ABC Waters Design Guidelines

Over the years, Singapore has developed a pervasive drainage network of 17 reservoirs and more than 8,000 km of drains, canals and rivers. To realise the full potential of this water infrastructure, PUB, the National Water Agency, launched the Active, Beautiful, Clean Waters (ABC Waters) Programme in 2006. This strategic initiative aims to harness the full potential of our waterbodies to improve the quality of not only our waters but also of our lives. By integrating drains, canals and reservoirs with the surrounding environment in a holistic way, the ABC Waters Programme aims to create beautiful and clean streams, rivers and lakes with picturesque community spaces for all to enjoy.

Since the inception of the ABC Waters Programme in 2006, we have seen many successful ABC Waters projects completed with many more in the pipeline. Our blue spaces are slowly being integrated with the urban fabric of Singapore. Yet, there remains a great deal of untapped opportunities: aside from our waterbodies and waterways, the catchment upstream has much potential to be unlocked. Going forward, proliferating or mainstreaming the ABC Waters concepts throughout the catchment will play an important role to improve the urban runoff quality and enhance the liveability of the urban environment as our city state continues to develop.

With investment in research and technology, Singapore has put in place a diversified and robust water supply through our Four National Taps, namely water from local catchments, imported water, NEWater and desalinated water. This diversification has allowed the nation to close the water loop, and helped her take a step towards water sustainability. It also forms the backdrop for ABC Waters, as Singapore moves beyond water sufficiency to capitalise on the potential of water to enhance the quality of life and to maintain the quality of water in our waterways and reservoirs.

ABC Waters Programme is a key example of our ongoing sustainable development efforts under the City in Nature pillar of the Singapore Green Plan 2030. Restoration of nature into the urban landscape is key to blue-green integration with the development of multifunctional stormwater management with development.

The aim of the ABC Waters Programme is to seamlessly integrate the Environment (Green), Waterbodies (Blue), as well as the Community (Orange) to create new community spaces and to encourage lifestyle activities to flourish in and around the waters. As the community gets closer to water, people will better appreciate and cherish our valuable water resource and hence develop a sense of stewardship towards water.

The three key strategies of the ABC Waters Programme are:

1. Development of ABC Waters Master Plan and Project Implementation

   Launched in 2007, the master plan guides the overall implementation of projects to transform the city’s utilitarian drains, canals and reservoirs into vibrant, picturesque and clean flowing streams, rivers and lakes that are well integrated with the environment. More than 100 potential projects across the island have been identified for implementation in phases by 2030. More than 50 ABC Waters projects have been completed by PUB as of March 2023.

2. Promoting Adoption of the ABC Waters Concept

   The ABC Waters Concept encapsulates Singapore’s ideology of harnessing the full potential of our waters and integrating them into our environment and lifestyles. A vital part of this concept is the implementation of ABC Waters design features, which are natural systems that detain and treat stormwater runoff on site before allowing it to flow into the waterways and reservoirs. At the same time, they enhance biodiversity and the living environment. To proliferate the concept, PUB encourages public agencies and the private sector to adopt ABC Waters design features in their developments to reap these environmental benefits and achieve sustainable stormwater management.

   The ABC Waters Design Guidelines was launched in 2009 as a call for partnership to encourage the private and public sectors to explore ways to implement ABC Waters design features and integrate waterways within their developments to enhance the environment. Over the years, PUB continues to update the Guidelines with more examples of projects and innovative designs.

   In 2010, PUB launched a new scheme, the ABC Waters Certification, to provide recognition to public agencies and private developers who embrace the ABC Waters concept and incorporate ABC Waters design features holistically in their developments. To date, many exemplary projects by public agencies and private sector have been certified and there are many innovative good designs in recent certified projects, signalling that the industry professionals have progressed in their capability on ABC Waters designs.

   In 2011, PUB and the Institution of Engineers Singapore (IES) rolled out the ABC Waters Professional Programme aimed at building the expertise of industry professionals in the area of ABC Waters design features. To date, there is a sizeable pool of ABC Waters Professionals who are trained to carry out ABC Waters design for developments.

   Moving forward, the direction is towards “mainstreaming” ABC Waters design to become a fundamental element of urban planning. The challenge is to chart the course to change ABC Waters design from a “good to have” option to a “vital public good” necessity that provides multiple benefits.

3. 3P (People, Public, Private) Partnership Approach

   The vision of attaining sustainable stormwater management would not be possible without buy-in from the community. PUB constantly engages the community to adopt and take ownership of Singapore’s waterbodies. For example, schools are encouraged to develop educational learning trails for the various ABC Waters projects so that students can learn and appreciate our waters more. Private companies, grassroots organisations and community groups also help to facilitate the trails and carry out various activities at our ABC Waters sites to encourage more people to enjoy the sites and related facilities in a responsible manner.

   

Create Communal Spaces and Areas

ABC Waters sites bring the community closer to water and create new recreational spaces for all to enjoy. Through adopting the ABC Waters concept, spaces near waterways and waterbodies are revitalised and enhance liveability. Blue-green integration creates a vibrant environment for residents and the greater community.

Enhance Aesthetics and Biodiversity of the Landscape

ABC Waters design features enhance the aesthetics and biodiversity of the landscape while slowing down the flow of stormwater runoff. This biophilic concept integrates nature into urban environment.

Detain and Treat Stormwater Runoff

ABC Waters design features are natural treatment elements to detain and treat runoff before it is discharged to downstream waterways and waterbodies. With upstream planning and seamless integration with the landscape and drainage system, both hydrological benefits and water quality improvement can be realised, in addition to other environmental benefits.

Educating the Public

At the core of the programme is the social aspect of getting the public involved in ensuring sustainability of scarce water resources by inculcating a sense of stewardship towards water. ABC Waters sites also provide experiential learning opportunities for the younger generation to learn about sustainable stormwater management.

Deploy ABC Waters Design Features to Meet Other Government Agencies’ Initiatives

ABC Waters design features are also recognised by other government agencies in meeting the requirements of their programmes.

The BCA Green Mark Certification Scheme provides a comprehensive framework for assessing the overall environmental performance of buildings to promote sustainable design. The scheme recognises ABC Waters design as one of the best stormwater management practices. Projects that attain PUB’s ABC Waters certification can be considered for points under Innovation.

Singapore receives about 2,500 mm of rainfall annually. Traditionally, the country negates the risk of flooding by channelling water into the reservoirs and the sea via a network of concrete canals and rivers. These rivers and canals are designed to quickly and efficiently convey stormwater runoff to the sea or the nearest waterbody. In the past, most waterways were designed as U-shape concrete channels to increase their conveyance capacity and reduce bank erosion. With continual urbanisation and climate change, stormwater runoff increases and the drainage channels need to be enlarged from time to time.

With two-third of Singapore’s land area as water catchment, it is important to improve surface water quality from urbanised catchment areas so as to ensure a cleaner water supply in Singapore’s reservoirs. Traditional concrete channel could do little in this aspect. As such, there is a need to develop a sustainable way to treat the stormwater runoff before channelling it into our reservoirs through the drains and canals.

Recognising that expanding canals and drains will not be sustainable, especially for areas that are more developed and have site constraints, PUB has gone beyond implementing pathway solutions (e.g. drain capacity improvements, diversion canals, centralised detention tanks and ponds, etc.) to work with developers to install source solutions (e.g. decentralised detention tanks and ponds, detention features, etc.) and receptor solutions in order to better manage stormwater runoff and protect developments from floods. By implementing a range of appropriate measures that cover the entire spectrum of the drainage system, flood risks can be significantly reduced and effectively managed.

To complement source solutions, ABC Waters design features also provide detention of stormwater and treat it closer to the source before it is discharged into public waterways.

A PUB R&D study “Derivation of Hydrological Curves for ABC Waters Design Features” in 2012 showed that ABC Waters design features designed for minor storms (such as those that occur 4 or more times a year on the average) could be very effective. They are able to detain and treat up to 85% of the annual rainfall volume of the catchment.

When adopted holistically as part of the drainage systems’ design, ABC Waters design features introduce additional flexibility within the system to cope with urbanisation and climate change. In particular, ABC Waters design features can be innovatively designed or integrated with other stormwater detention systems (i.e. detention tanks, stormwater ponds, etc.) to shave off the peak flows generated by intense rainfall. When implemented on a catchment-wide basis, they could reduce the risk of flooding at the development site and the larger catchment area. In addition, the features remove pollutants to mitigate the deterioration of runoff quality due to urbanisation.

Individual developments are therefore encouraged to implement ABC Waters design features to mitigate the impacts of urbanisation on waterbodies downstream. These environment-friendly features like rain gardens, bioretention swales and wetlands not only improve water quality, but also enhance the biodiversity and aesthetics of the surroundings (Refer to Chapter 4 for more details).

In Singapore’s highly urbanised environment, many developments are largely made up of impervious surfaces such as roofs, parking lots, streets and sidewalks that do not allow stormwater to infiltrate into the ground. With increased urbanisation, the replacement of green areas with impervious areas generates increased runoff that enters the stormwater drainage system. As a result, during intense storms, peak runoff from the urbanised catchment may exceed the design capacity of public drains, resulting in flash floods. Source solutions such as decentralised detention tanks and ponds provide temporary storage of stormwater on-site. This water is released at a controlled rate to the downstream drainage system.

In addition to reducing peak runoff, a detention tank can also be combined with a rainwater harvesting system to provide storage for non-potable reuse such as irrigation, external area washing, etc. Developers are encouraged to incorporate localised rainwater harvesting and on-site re-use of harvested water in their developments.

Managing the water quality of the harvested rainwater is an important consideration for a sustainable rainwater harvesting scheme. ABC Waters design features offer the advantage of water quality improvement via natural means. By channeling the runoff through these features, water is temporarily detained and pollutants are removed. The treated water can be collected and used for non-potable purposes.

When planners, architects and engineers include ABC Waters concepts in the upstream process of planning, there is an opportunity for building a holistic stormwater system that serves multiple functions of detention, treatment and drainage of stormwater runoff in a development. Combining architecture, landscape design and engineering, such integrated approach can create flexibility in the system and remove downstream implementation challenges. The example of Waterway Ridges, a collaboration between the Housing Development Board (HDB) and PUB, piloted the large scale implementation of ABC Waters design in a holistic manner within a public housing precinct.

With the success of Waterway Ridges, HDB has incorporated ABC Waters design in many public housing and mixed developments. Many housing precincts in Tengah New Town have obtained ABC Waters Certification (Gold) subsequently, demonstrating HDB’s commitment to sustainability.

ABC Waters design are part of green living in Singapore. ABC Waters design features are eco-friendly features for natural cleansing of stormwater runoff before it is reused within the development or channeled into our waterways and reservoirs. Such features also enhance biodiversity and contribute to creating a biophilic living environment for our residents.

As ABC Waters design progressively becomes entrenched as planning norms to be adopted, Singapore started to see more seamless and upscaling of ABC Waters projects. With wider adoptions by developers and the pervasive incorporation of ABC Waters design features throughout the whole water catchment, Singapore can realise the full potential of the ABC Waters management strategy in ensuring slower and cleaner runoff in our waterways and waterbodies.

This chapter highlights the key considerations that the designer should be familiar with when adopting the ABC Waters management strategy. These include:

• Surface water drainage

• Source solutions to manage stormwater on-site

• Flood control

• Stormwater quality

• Site safety and public health risks

The designer should also refer to the following documents listed below. To access the document, you may refer to Chapter 9 - Appendices.

• The Engineering Procedures for ABC Waters Design Features, which forms an integral part of the ABC Waters Design Guidelines. This publication gives specific guidance on selection, sizing, construction and maintenance of the ABC Waters design features.

• The Code of Practice on Surface Water Drainage, which specifies the minimum requirements for the surface water drainage systems of new developments.

• The Drainage Handbook on Managing Urban Runoff, which explains PUB's stormwater management strategies to manage flood risks.

• On-site Stormwater Detention Tank Systems Technical Guide

• The Code of Practice on Environmental Health, which addresses various aspects of anti-mosquito breeding.

1. Internal Drainage System

   All runoff within a development site must be discharged into a roadside or outlet drain/waterway. A system of internal drains is required to intercept, convey and discharge all runoff from the development site into the roadside or outlet drain.

   Any overflow, by-pass and treated runoff from ABC Waters design features, including constructed wetlands and retention ponds, could be stored on-site for reuse. Any excess water must subsequently be discharged to a roadside drain or an outlet drain/waterway.

   From October 2023, developers/owners for all developments greater than or equal to 0.2 hectare in size are required to manage their peak runoff by implementing on-site detention measures (e.g. detention tanks and/or ABC Waters design features) to hold back or slow down runoff before discharging it to the public drainage system in a regulated manner. These on-site detention measures will complement PUB’s on-going drainage improvement works to provide a higher level of protection against flood risks in the catchments.

2. Structure within or adjacent to a Drain/Drainage Reserve

   Subjected to the approval of PUB, ABC Waters design features can be located within/adjacent to the drainage reserve or adjacent to a drain. The following conditions apply:

   • The affected drain must meet the required hydraulic capacity or be upgraded in size.

   • All foundation structures must be independent. The foundation structures must be stable when excavations up to 1.0 m below the invert or proposed invert of the affected drain are carried out. The structures must be kept at least 300 mm away from the drainage structures.

3. Natural Hydrological Features

   Existing site conditions may present opportunities naturally conducive for the implementation of ABC Waters design features, for example:

   • Areas of permeable soil suited for infiltration

   • Existing vegetation that can function as bio-filters

   • Land forms (e.g. natural depressions)

   The designer could capitalise on the site condition for environmentally friendly and sustainable design.

1. Consideration for Flood Control

   The following criteria must be met to address public safety and protection of property:

   • Use of the Rational Formula to compute the peak runoff from the catchment. The peak runoff from design storms shall be used to size the overflow system for ABC Waters design features if the features are designed to cater for small frequent storms (such as 1 in 3 months storms or storms that occur 4 times a year, on the average).

   • Use of Manning’s Formula to compute the size of incoming and outgoing drains/ pipes connected to the ABC Waters design features.

   • For effective use of land, the ABC Waters design features can be designed for treatment of frequent storms. Proper by-pass and overflow system from ABC Waters design features should be provided and connected to the storm drain so that the surrounding area will not be flooded. The downstream storm drain should have adequate hydraulic capacity to cater for the peak f lows from the catchment of ABC Waters design features.

   • The minimum engineering requirements for surface water drainage are specified in the latest edition of the Code of Practice on Surface Water Drainage.

2. Consideration for Water Quality Improvement

   The stormwater quality objectives or the performance targets of ABC Waters design features are directed at the protection of urban waterbodies in Singapore such as the Marina Reservoir, Punggol Reservoir and Serangoon Reservoir etc. It is desirable that new developments incorporate ABC Waters management strategies that minimise the impact of the development on our waterways and reservoirs.

   POLLUTANT	STORMWATER TREATMENT OBJECTIVES
   Total suspended solids	80% removal or less than 10 ppm
   Total nitrogen	45% removal or less than 1.2 ppm
   Total phosphorus	45% removal or less than 0.08 ppm

Table 3.1 Stormwater quality objectives for Singapore

• Stormwater quality objectives may be revised as more monitoring results are gathered over time

  Performance curves developed to guide professionals in the design of ABC Waters design features are available in the Engineering Procedures for ABC Waters Design Features.

  The stormwater quality objectives have been developed to represent practical targets. In Singapore, based on preliminary assessment and monitoring of pilot projects, the objectives as shown in Table 3.1 have proven to be achievable. Achieving these objectives is a practical approach to institutionalising best practices in stormwater quality management.

3. Site Investigation

   Site investigation, including, but not limited to, topography, soil property test, groundwater table and services detection, are to be carried out before commencing physical works on site. It is necessary to take note of abnormalities or hindrances observed during site investigation so that design can be reviewed to suit site condition. This will also minimise delay of work during construction stage.

4. Plant Selection

   Plants are essential for the proper functioning of ABC Waters design features. Plants help to stabilise swales and batter slopes and maintain the infiltration capacity of the filter media. Not all plant species are suitable for all these functions. A list of plants that are used for the filter media in bioretention systems is in Chapter 6 of the Engineering Procedures for ABC Waters Design Features. The list can serve as a guide but their suitability, based on site conditions, must still be assessed by the designer. Designers can also make reference to “Sustainable Landscape”, a publication by the Centre for Urban Greenery and Ecology (downloadable from NParks website https://www.nparks.gov.sg/-/media/cuge/ebook/sustainable-landscape/ sustainable-landscape.pdf).

   1. Within Treatment Area

      Plants with fibrous roots are generally better in keeping the infiltration capacity of the soil media. Hardy plants, that can survive in sandy and low-nutrient soil as well as wet conditions, are required for features like bioretention systems that get inundated during rain events. Water plants are suitable for constructed wetlands. Additional considerations include capability of plant species for better removal of pollutants like nutrient and heavy metals.

   2. Channel and Batter Slope

      Ground covers are normally used for vegetated swales and batter slope of bioretention systems to prevent soil erosion. Tall plants are normally not recommended for the flow channel of swales, as they obstruct the flow of runoff and increase the roughness coefficient of the channel.

   3. Surrounding Area

      • Use shrubs as soft barrier around bioretention systems, especially when there is a steep slope or a big drop in level.

      • To minimise the usage of thorny plants (eg: Caesalpinia pulcherrima) alongside footpath.

      • To minimise encroachment of plants onto footpaths with a buffer zone along planting verges that abut the path edges.

      • To minimise usage of hefty and large growing plants at corners (potential blind spots).

      • Avoid having long stretches (>20m~) of monoculture planting to minimise undesirable pest issues that targets specific species (for example, planting one species of Ipomea pes-caprae along the whole stretch of a waterway could attract large swarms of leaf footed bugs).

5. Provision of Maintenance Access

   1. Maintenance gates for workers to access workzones beyond railings

   2. Vehicular maintenance access (if necessary)

6. Subsoil Pipes

   Subsoil pipes shall be provided with standpipes for flushing and connected to a sump (either overflow or a separate sump) instead of discharging directly into surrounding drains for ease of maintenance checks.

7. Inlet Zone

   Provide a forebay at point inlets of features to prevent scouring / erosion and facilitate sedimentation. The overflow and outlet of the feature shall be positioned away from the inlet as to prevent short circuiting of flow path.

8. Gravels

   Gravels used in the forebay or bottom of swales are to be appropriately sized or embedded to prevent being washed away.

9. Safety Considerations

   A risk and safety assessment shall be conducted to identify potential safety hazards that might occur after the implementation of stormwater management measures. It is foremost to put public safety as the most important consideration and is the responsibility of the developer and / or Qualified Person (QP) to ensure that all applicable safety standards are met and a system of safety is set up and in place. The designer shall develop a risk assessment form or a safety design checklist to check the safety aspect of the design. The checklist should be reviewed early during project development, and identify factors in the design that ensure safe construction, operations and maintenance. Inputs from the construction team and maintenance agent should be sought when drawing up the checklist.

Rainwater is relatively clean. When it comes in contact with the surfaces of a catchment, it picks up sediments, nutrients and other impurities. Typically, stormwater runoff is conveyed by drains and canals into reservoirs for storage or to the sea without treatment.

With the use of ABC Waters design features, this runoff will be temporarily detained and cleaned before it flows into waterways and reservoirs. In essence, ABC Waters design features help to minimise the hydrological impact of urbanised catchments, and safeguard water quality in our reservoirs and waterways. They also beautify the surroundings while improving biodiversity. With water catchment areas covering two-thirds of Singapore's land, it is critical that ABC Waters design features are incorporated into the development plans.

In this section, we will examine the elements involved in a typical stormwater passage and discuss the following elements in detail:

4.1 Catchment Elements

4.2 Treatment Elements

4.3 Conveyance and Storage Elements

The surfaces found in our urban environment (catchment elements) vary and can be categorised broadly as architectural structures (buildings, shelters), circulation infrastructure (vehicular roads, bicycle paths and pedestrian walkways) and open spaces (urban plazas, parks).

In this section, we will discuss the planning strategies involved and the various ABC Waters design features that could be integrated into the various catchment elements.

Before starting the design of a development, it is essential to understand the constraints and potential of the site and factors that would affect stormwater flow:

• Topography (natural slopes/depressions)

• Geology (soil type and quality – porosity, infiltration and conveyance properties)

• Internal drainage, sub-catchments and the connection points to public drains.

The design of a development is also bound by basic urban planning parameters such as site coverage, plot ratio, height restrictions, and land use. Blue-green integration at the start of the masterplan or site design is optimal for integration at the planning stage, whether it is planning for a masterplan of a mixed-use district, housing precinct, or individual plot scale.

In addition to being part of a sustainable stormwater management system, it is important that ABC Waters design features complement the land use requirements and functions of the space. For example, rain gardens can serve as multi-functional blue-green design features that can hold and treat run-off as well as enhance the landscape. There are many benefits to blue-green integration. ABC Waters design features can be used to meet source control requirements and help to relieve pressure on existing stormwater drains. This is showcased in Case Study 10.2: Alkaff Lake.

Due to urban planning parameters, various spatial configurations, each with a different landscape strategy, can be employed, as illustrated in the diagrams below. Design elements and ABC Waters design features can be customised for each of the different landscape strategies employed. This will be elaborated upon in the subsequent sections.

The diagram above illustrates how the different catchment elements and ABC Waters design features can be integrated holistically in our urban landscape. Holistic blue-green integration is best achieved at the early planning stages with consideration of platform levels, building design, drainage, circulation & open space. Opportunities for co-location of different ecosystem services are best discussed during planning for a smooth implementation process and subsequently, maintenance regime.

In Singapore, the most common applications of ABC Waters design features for buildings can be located at the following building elements:

• Rooftop

• Sky garden or terrace

• Balcony

• Planter box

• Ground level greenery

• Green wall/ Vertical Greenery

To implement the ABC Waters design concept, different ABC Waters treatment elements can be applied to each of the building elements mentioned above or in combinations.

Intensive Green Roofs

Intensive green roofs are large green spaces at rooftops that are designated as recreation areas. The development of public recreational spaces and gardens on the rooftops of commercial buildings has had a long history in Singapore and continues to be highly popular. Examples include Orchard Central, Suntec City and VivoCity. Nowadays, green roofs have gained popularity in public and private residential developments as well as utility developments.

There is, however, greater potential for synergistic integration of greenery, water features and the building itself. Plants can serve many functions apart from creating aesthetically pleasing environments.

Stormwater runoff can first be collected and cleansed (using rain gardens or vegetative filtration planter) on the roof, then channelled to the various water features on lower levels. Alternatively, the cleansed water can be used to irrigate the plants on the planters and balconies, or for the washing of pavements and walkways.

Extensive Green roofs

An extensive green roof is a low-maintenance vegetated roof system that uses hardy ground-cover plants and a lightweight plant growing medium with shallow drainage/storage layer to store rainwater that could be supplied to plants when there is no rain. It is not designed as a recreational space.

As a result, less water runs off the roof as compared to conventional rooftops without any extensive green roof. In addition to conserving potable water for irrigation and improving air quality, extensive green roofs also cool down buildings and reduce the “heat island” effect by providing a permeable and moist layer to shade the building from sunlight.

The Housing & Development Board (HDB) has piloted extensive green roofs in existing HDB public housing blocks since 2006 to reduce heat build-up on exposed concrete roof surfaces in public housing estates. Besides enhancing the greenery in estates, it also helps to slow down stormwater runoff.

Balconies, Planter Boxes and Vertical Green

The use of treatment elements does not have to be limited by the lack of space. Cleansing biotopes and bioretention planter boxes can be implemented in a tiered or multi-level and sequential system to achieve the high purification standards.

Currently in Singapore, individual families and collective residential bodies (facility-managed condominium or apartments) alike have shown keen interest in incorporating vertical greeneries into the living environment.

These existing trends could be combined with sustainable stormwater management to harness effective stormwater harvesting capabilities with improved water quality.

The following is an example taken from Kampung Admiralty, where multi-level vegetative filtration planter boxes cleanse runoff from the roof while creating a pleasant atmosphere in the building all year round. The cleansed water is stored in the rainwater harvesting tank that provides irrigation water.

Overflow from the harvesting tank is channelled to ABC Waters design features (such as vegetated swales, cleansing biotope) at ground level, which are integrated with the plaza.

The typical road in Singapore comprises carriageways that are sloped towards either the roadside kerbs or central dividers, where drop inlet chambers channel the stormwater runoff into drains and culverts that bring it to the main stormwater canals.

Bioretention swales and basins can be incorporated relatively easily and employed effectively in this situation, not only for detention purposes (to slow down the flow of runoff into the drains and canals), but also as a way of cleansing stormwater runoff before it is discharged to roadside drains.

For small catchments, vegetated swales can be used as roadside drains to convey the runoff. The swales slow down runoff and allow some sediments to settle.

Existing roads (including side verges) in Singapore typically comprise footpaths, carriageways, green verges and roadside drains running in parallel alongside each other. Where there is sufficient space (e.g. a road beside a park), footpaths can be made to meander and integrate with drains or design features as a way of enhancing the experience of the pedestrian.

Analysis of a typical plaza

Analysis of a typical plaza Public plazas are common features in Singapore’s urban landscape, particularly in commercial and retail spaces where large crowds gather, such as Orchard Road and Shenton Way. The following are common but unsustainable approaches to the design of a typical plaza:

1. Separation of landscape and hydrology

   In Singapore, landscape and hydrology are often kept as separate systems in the design of urban public plazas. Water features are common but they are seldom natural elements. They are typically tiled concrete pools with little or no landscaping. Where plants are included in these water features, they remain only as aesthetic elements, often planted in separate pots and planters.

2. Separation of recreational water feature and stormwater management system

   Fountains are increasingly provided for recreation in public plazas. However, they play mostly aesthetic roles. They seldom take on stormwater management functions, and are usually replenished with fresh tap water, thus adding to potable water consumption.

An integrated plaza with ABC Waters design features

The ABC Waters concept of integrating the environment, waterbodies and the community, albeit on a smaller scale, would be simple to implement and help to develop a more efficient and sustainable plaza design. Specifically, they contribute to the following design factors:

1. Cleansing

   The plants take on a cleansing or treatment function for runoff that improves water quality by uptaking nutrients and other pollutants.

2. Detention

   ABC Waters design features are green features that slow down runoff. Rain gardens, wetlands and other features can be designed to provide detention of stormwater runoff and reduce the size of structural detention tank.

3. Low Maintenance

   ABC Waters design features are self-sustaining natural systems that require minimal maintenance.

4. Aesthetics

   While meeting stormwater treatment and management functions, ABC Waters design features, with the integration of water features and plants, provide a dynamic yet relaxing environment for social enjoyment and enhanced biodiversity.

Treatment elements (or ABC Waters design features) can be applied to urban components to slow down, detain or retain the first flush of stormwater runoff while simultaneously cleansing it.

They are cost-effective, natural and environment-friendly green features for sustainable stormwater management. The cost is a small percentage of the total capital cost of the development, while the resulting environmental benefits are many.

As ABC Waters design features are natural systems of plants and soil, minimal maintenance is required. Please refer to “Engineering Procedures for ABC Waters Design Features” for generic maintenance requirements. The document also gives guidance on selection and sizing of the treatment elements with worked examples and checklists.

Every treatment element covered in this chapter has different water treatment or cleansing capabilities. They cleanse runoff either in one or a combination of the processes described in Table 4.1. For example, a sedimentation basin has negligible ability to remove fine particles or soluble nutrient compounds, but is very effective in allowing large to medium size pollutants to settle and be separated.

Each treatment element can be understood in two basic properties:

1. What treatment process(es) it primarily employs (sedimentation, filtration or biological uptake)?

2. What is its primary stormwater management function (conveyance, detention or retention)?

Introduction

Vegetated swales are natural drainage channels with mild slope. They are used to convey stormwater via overland flow at a slower speed to allow settlement of sediments. They protect downstream treatment elements or waterways from damage by erosive flows from frequent storm events because flow velocities are slower for vegetated swales than concrete-lined drains. They can be used in combination with bioretention systems (eg. located upstream of a bioretention swale).

Application and Principles

Vegetated swales are widely applicable at residential estates, parks and other sites. The landscape design of vegetated swales addresses stormwater quality while incorporating landscape functions. As such, it is important that vegetated swales are carefully designed to integrate with the characteristics of the surrounding landscape. In Singapore, where rainfall intensity is high, vegetated swales are applicable for small catchment areas (e.g. small perimeter or compound drains, park drains and roadside drains near the summit point or use with an overflow system).

The interaction between stormwater flow and vegetation within the vegetated swales facilitates the settlement and detention of coarse to medium-sized solids in the stormwater runoff. Vegetated swales alone usually cannot provide sufficient treatment to meet stormwater treatment or water quality objectives as it has limited capability to remove soluble nutrients. However, vegetated swales are particularly good at removing coarse sediments and can provide the necessary pre-treatment for downstream treatment systems such as wetlands and bioretention systems.

Benefits

• Reduces flow velocities and remove solids like stones and other particles to protect downstream waterways from erosive flows during storms.

• Provides effective pre-treatment for downstream ABC Waters design features like bioretention swales, rain gardens or constructed wetlands.

• Beautifies the surrounding landscape, integrates well with green area and provides drainage.

• Functions as a cost-effective natural drainage system for small catchments.

Operation & Maintenance

Vegetated swales have a flow conveyance role that needs to be maintained to ensure adequate flood protection. In this regard, a key maintenance requirement is to ensure that the cross-section and longitudinal profile of the vegetated swale are maintained and that it is not subjected to erosion or excessive deposition of debris and sediments or overgrown vegetation that may impede the passage of stormwater.

Maintenance of vegetated swales primarily consists of:

• Routine inspection of inlet and overflow points to clear any blockage

• Routine removal of litter, debris and sediments

• Maintain the height of vegetation within the flow channel

• Routine inspection and repair of the vegetated swale profile

• Maintaining healthy vegetation growth – regular care, such as weeding, mowing, pruning and pest-control, is necessary

• Removal and management of invasive weeds

• Irrigation may be needed during drought

Introduction

Bioretention swales are vegetated swales with bioretention systems located within the base. They provide efficient treatment of stormwater runoff and are designed with gentle gradient and temporary ponding (extended detention) to facilitate infiltration. Runoff is cleansed as it percolates downwards. The filtered water is then collected by perforated subsoil pipes and re-used on-site or conveyed to downstream waterways.

Application and Principles

Bioretention swales can be widely applied to treat runoff from roads, carparks, residential, commercial, industrial areas and parklands, etc. They could form attractive streetscapes and landscape features in many urban developments.

Surface runoff is first filtered through the surface vegetation, removing coarse to medium sediments. It then percolates through a filter media where fine particles are removed and soluble nutrients are taken up by the plants and soil microbes. Vegetation plays a key role in maintaining the porosity of the soil media of the bioretention system and also in the taking up of nutrients from the percolating surface runoff. The plants selected must be able to withstand both wet and dry conditions. They should have fibrous root systems to help keep the filter media porous. It is preferable for plants with good nutrient removal capabilities to be selected.

Benefits

• Reduces flow velocities and settles coarse sediments

• Encourages habitat creation and promotes biodiversity

• Beautifies surrounding landscape

• Filters and cleanses water naturally without the use of any chemicals

Operation & Maintenance

Bioretention swales have a flow conveyance role that needs to be maintained to ensure adequate flood protection. In this regard, a key maintenance requirement is to ensure that the shape and slope of the bioretention swale are maintained and that it is not subjected to erosion or excessive deposition of debris and sediments that may impede the passage of stormwater. The inlet points and overflow points or pits have to be kept clear.

Maintenance of bioretention swales primarily consists of:

• Routine inspection and repair of the bioretention swale cross-section and longitudinal profile

• Routine inspection of inlet and overflow points to clear any blockage and repair any damage.

• Routine removal of litter, debris and sediments

• Maintain the height of vegetation within the flow channel

• Raking of the bioretention swale surface and flushing of the subsoil perforated pipes if there is evidence of clogging

• Maintenance of healthy vegetation growth, as it plays a key role in maintaining the porosity of the soil media and the taking up of nutrients from percolating surface runoff. Regular care such as irrigation, weeding, mowing, pruning and pest-control is necessary.

To facilitate ease of construction at tight sites, a modular bioretention swale can be used. A modular bioretention swale consists of three basic modules: an inlet module, middle modules and an outlet or overflow module. The inlet module contains an inlet pipe to direct stormwater runoff from the catchment area into the bioretention facility. The middle modules are connecting modules to join the inlet module to the outlet module. The number of middle modules added depends on the size of catchment area and the desired length of the swale. The outlet or overflow module allows stormwater runoff to overflow when the influent stormwater runoff exceeds the designed capacity of the swale. The subsoil drainage pipe runs through all the modules installed and discharges at the outlet module.

Such a design facilitates easy construction as the system can be manufactured offsite and assembled on-site to shorten construction time. Fig 4.30 shows the typical cross-section of a modular bioretention swale system.

Bioretention basins or rain gardens are vegetated land depressions designed to detain and treat stormwater runoff. Their treatment process is the same as bioretention swales; the runoff is filtered through densely planted surface vegetation and then percolated through a prescribed filter media (soil layers). Unlike bioretention swales, they do not convey stormwater runoff.

Application and Principles

Similar to bioretention swales, impurities are removed through sedimentation, f iltration and some biological uptake (by plants, bacteria, etc). Rain gardens can be installed in various scales and shapes: in planter boxes or integrated with streetscapes. They can also act as ‘standalone’ soil filtration systems within residential areas, parklands, schools, carparks and other developments.

As the bioretention basin is configured for the removal of finer particles and soluble pollutants, it is advisable that a small sedimentation basin (refer to Section 4.2.4) or a vegetated swale be constructed upstream of the bioretention basin as a pre-treatment measure to remove coarse to medium-sized sediments. This helps to ensure that the treatment efficiency of a bioretention basin is sustained over time, and minimises the maintenance requirements of the bioretention basin. If space is limited, a sedimentation forebay can be included as an integral part of the rain garden.

The vegetation in a bioretention system is a vital functional element of the system both in terms of maintaining the hydraulic conductivity of the filter media and the taking up of nutrients. The plants selected for bioretention basins should have f ibrous root systems to help keep the soil porous, and be able to withstand wet and dry conditions. It is also good to select plants with good nutrient-removal capabilities.

Soak Away Rain Garden

Typically, subsoil pipes are installed in the drainage layer to discharge the filtered water to a nearby drain. However, if there is no suitable drain nearby, a soak away type of rain garden can be used if the surrounding soil is adequately permeable. A soak away rain garden is easy to construct as it only has one filter layer and no subsoil pipe. It is suitable for small developments like schools or even private homes. Test-bedding of soak away rain garden has been carried out. The results showed that to achieve the water quality objectives (Section 3.2), a larger treatment area is needed for soak away as compared to the conventional rain gardens for the same catchment.

Benefits

• Ease of design

• Encourages habitat creation and promotes biodiversity

• Beautifies surrounding landscape

• Filters and cleanses water naturally without the use of any chemicals

Operation & Maintenance

Vegetation plays a key role in maintaining the porosity of the surface of the f ilter media and the taking up of nutrients from percolating surface runoff. It also facilitates the transport of oxygen to the soil microbial communities for the biological transformation of pollutants. Thus, a well-covered healthy growth of vegetation is critical to its performance.

Maintenance of bioretention basins primarily consists of:

• Maintenance of depression profile to keep a clear flow path to and through the bioretention basin

• Routine inspection of inlet, outlet and overflow points to clear any blockage

• Routine removal of litter, debris and sediments from the forebay

• Raking of the bioretention basin surface and flushing of the subsoil perforated pipes if there is evidence of clogging

• Maintaining healthy vegetation growth, as it plays a key role in maintaining the porosity of the soil media and the taking up of nutrients from the percolating surface runoff. Regular care such as irrigation, weeding, mowing, pruning and pest-control is necessary. It is good to use a variety of plants to control plant damage by pests.

Introduction

Sedimentation basins are ponds that provide temporary detention or longer time retention of stormwater runoff as well as reduction of the flow velocity to promote the settling of particles by gravity. They are designed to capture 70 to 90% of coarse to medium-sized sediments (typically above 125µm). The settled sediments can then be removed periodically. Sedimentation basins are used as pre-treatment features for constructed wetlands and bioretention basins. Larger sedimentation ponds can be used as water storage ponds or pre-treatment upstream of aesthetic water features if integrated with lush landscape. At the same time, sediments are settled in the pond and cleaner water in the upper part can be channelled for use like irrigation.

Application and Principles

Sedimentation basins can be permanent water features in an urban setting or temporary measures to control sediment discharge during construction. Its primary function is to capture coarse to medium-sized sediments as a pre-treatment measure before the water enters a downstream treatment system (e.g. macrophyte zone of a constructed wetland or a bioretention basin) configured for the removal of f iner particles and soluble pollutants.

The second function of sedimentation basins is to control or regulate flows entering the downstream treatment system. The outlet structures of sedimentation basins are designed such that flows up to the design flow will enter the downstream treatment system, whereas excess flows are bypassed around the downstream treatment system (e.g. via a spillway). In providing this function, the sedimentation basin protects the downstream treatment system against scouring and other damages during extreme high flows. It can also be used as a stormwater detention pond.

Benefits

• Pre-treats the runoff to facilitate further treatment by downstream ABC Waters design features

• Slows down the runoff to protect downstream features and waterways

• Provides easy sediment removal

• Can be designed as an aesthetic water feature with wetland plants around the edge

• Stored water for detention purpose and for non-potable uses

Operation and Maintenance

• Ensuring proper operation of inlet scour protection or energy dissipation structures

• Monitoring of sediment accumulation and timely removal of sediment

• Removal of debris to ensure that outlet is not blocked

• Weed management to ensure the healthy growth of species as required in the design of each specific site

Introduction

The use of constructed wetlands for stormwater management is widely adopted in many urban and rural areas. Constructed wetland systems are shallow and extensively vegetated waterbodies that generally consist of the following zones:

• An inlet zone (designed as a sedimentation basin to remove coarse to medium- sized sediment – see Section 4.2.4)

• A macrophyte zone (a shallow heavily vegetated area to remove fine particles and soluble pollutants)

• A high flow bypass channel (to protect the macrophyte zone)

Constructed wetlands are designed primarily to remove suspended particles and dissolved contaminants. The wetland needs to be configured such that system hydraulic efficiency is optimised, healthy vegetation is sustained and a balance eco-system is maintained.

Application and Principles

Wetlands can be constructed on different scales, from building scale, park scale to large regional systems. The design of constructed wetlands is scalable according to the size of the contributing catchment and this has made its application extremely versatile. In highly urbanised areas, they can have a hard edge form and be part of a streetscape or forecourts of buildings. In regional settings, they can be over 10 hectares in size and provide significant habitats for wildlife.

Wetland processes involve slowly passing runoff through heavily vegetated areas. Sediment settles and plants filter fine sediments and uptake soluble pollutants from the runoff. Microorganisms that grow on the plants and soil can absorb nutrients and other associated contaminants from the runoff.

In Singapore, wetlands can perform very efficiently due to warmer climate, faster plant growth and other biological activities.

In general, wetlands can be categorised into surface flow, sub-surface flow and floating wetlands. Among them, the surface flow wetland is most suitable in treating surface runoff for sustainable stormwater management. Wetlands also create habitats and promote biodiversity.

1. Surface Flow Wetland

   A small scale surface flow wetland comprises a shallow marsh of mainly emergent water plants through which water slowly flows. The water level is kept at a fairly constant depth. The plants help to remove impurities in the water, resulting in cleaner water at the outlet.

2. Sub-surface Flow Wetland

   In this wetland, no water can be seen as it is flowing below the surface, through the filter media, which retains suspended solids. The roots of the plants absorb impurities in the water, thereby cleansing it. The filter media sustains a vast bacteria population that can consume and break down pollutants. This wetland type is typically used to cleanse water with more organic content.

3. Floating Wetland

   A floating wetland is an engineered system that employs plants growing on a floating mat on the surface of the water. Rooted emergents (plants that grow in water with leaves and flowers above the water surface) are selected for planting on floating wetlands.

   The plant’s roots also serve as a natural environment (or substrate) for the growth of a community of microorganisms that breaks down organic pollutants in the water.

Benefits

• Filters and cleanses water naturally without the use of any chemicals

• Encourages habitat creation and promotes biodiversity

• Beautifies surrounding landscape

Operation and Maintenance

• Maintain continual flow to and through the wetland system

• Maintain vibrant vegetation. Suitable plants must be chosen for survivability and ability to remove pollutants like nutrients

• Routine removal of accumulated sediment

• Routine weeding, removal of dead plants and harvest of overgrown plants

• Routine removal of litter, debris and sediments

• Inlet zone needs to be maintained in the same way as the sedimentation basins

Introduction

Cleansing biotopes are a form of artificially constructed vertical flow wetland, typically with recirculation. They consist of nutrient-poor substrates that are planted with wetland plants that are known for their water cleansing capacity.

Application and Principles

Cleansing biotopes can be implemented in a variety of situations, such as in the revitalisation of lakes and the cleansing of urban waterbodies. They can also be added in outdoor areas such as parks, open fields, ponds and lakes. Areas such as rooftop gardens, gardens in building interiors, open plazas next to buildings or even under elevated structures can also be integrated with such features. The cleansing biotope can be subdivided into smaller areas (such as small sky gardens and planters) that work together in sequence for incremental cleansing.

The degradation of pollutants in a cleansing biotope occurs with the help of microorganisms within the substrate that is fed by oxygen from the root zones of the wetland plants. The layers of substrate filter out particulates and have mineral composites that bind and remove phosphates. The dense planting also filters out sediment while partially feeding off and removing nutrients in the water. If higher water quality is needed, the cleansed water is often recirculated for another pass through the cleansing biotope.

Benefits

• Filters and cleanses water naturally without the use of any chemicals

• Encourages habitat creation and promotes biodiversity

• Beautifies surrounding landscape

• Achieves high water quality by multiple passes

Operation & Maintenance

• Routine weeding, removal of dead plants and harvest of overgrown plants.

• Routine removal of litter, debris and sediments.

• Maintain healthy vegetation growth, as it plays a key role in maintaining the porosity of the soil media, taking up of nutrients and promoting the growth of microorganisms that degrade pollutants from the percolating surface runoff. Regular care such as irrigation, weeding, mowing, pruning and pest-control is necessary.

• Cleansing biotopes can be divided into several areas that are alternately activated. This allows each section to be deactivated regularly for regeneration.

• Under extreme conditions, the filter media may become clogged at the surface by organic matter. When this happens, the water feed is switched off or diverted to allow the substrates and organic matter to dry for several days and the biotopes surface to be mineralised. The top layer of the filter media should also be raked to loosen it. The cleansing biotope system can then be turned on again.

Singapore’s extensive stormwater network comprises of 17 reservoirs and more than 8,000 km of canals and drains.

Without attempting to exhaust the many possible permutations of the ABC Waters elements, this section aspires to demonstrate some of the many possible interventions that can be applied to waterways and waterbodies.

It is, however, important to note that there are many factors that influence the feasibility and suitability of implementing specific ABC Waters elements, including the following:

1. Land Use

   • Affects the kind of pollutants

     Stormwater pollutants from urban development originate from a variety of sources in the catchment. Suspended solids are mainly from soil erosion; nutrients, organic matters and microorganisms are from sullage discharge, animal droppings and fertilisers; oils are generally from vehicles and petrol stations; litters are from populated areas and dry leaves are from landscaped areas. Suspended solids, nutrients, organics, oils and litters have a negative aesthetic impact, which is often a cause for concern for the community.

   • Affects facilities and activities

     Recreational facilities are commonly integrated along the edges of rivers close to business or residential areas, and reservoirs that are close to residential areas. On the other hand, rivers and reservoirs within and close to the nature reserves, such as Sungei Buloh and Kranji Reservoir, are kept tranquil and natural to benefit the flora and fauna community found there.

   • Affects quantity of runoff

     The high density of buildings and paved areas has an inverse effect on stormwater infiltration levels, and increase the runoff rates. Detention of stormwater on-site is necessary for urban developments and ABC Waters design features can be used as detention measures.

   

2. Soil and Geological Condition

   The composition of soil has an effect on a variety of properties. Soil that is predominantly clay in nature would impede infiltration but facilitate conveyance. It would also be more plastic and can sustain a steeper slope along banks and in landforms. However, it may not be as suitable for bioengineering as plants may not thrive due to the lower porosity and hence decreased capacity for containing oxygen.

   Surface roughness of the coarse soil that contains larger rocks and aggregates would also decrease the velocity of the water flow as compared with a concrete-lined canal.

3. Ecological Integration

   Each canal is part of a larger drainage system and catchment area. Careful analysis to determine the effect of any intervention on upstream and downstream conditions prior to any changes is imperative.

   The biodiversity of a natural system is highly sensitive and susceptible to the slightest change. Careful studies to identify existing species of plants and animals would ensure the preservation of the delicate ecological balance.

1. Incorporating Amenities to Bring People Closer to Water

   Areas next to waterways can be transformed into attractive promenade spaces to encourage the community to enjoy our waterways. Amenities such as benches, pavilions, look-out decks and other outdoor facilities can be added to bring people closer to the water edge. These amenities can also be used to improve connectivity and accessibility to the water.

2. Greening of Waterways

   A technique that can be used to enhance waterways without demolition of the concrete canal is the greening of waterways with the use of creepers and shrubs. These have been implemented by PUB at some of the canals in Singapore and an example is shown below.

   

   Another method to green our waterways and improve aesthetics is via the use of gabions, which can be integrated into canal walls that are partially removed. The combination of a natural material (e.g. stones in the gabions) and the lush creepers enhance the overall look and feel of the waterway. This is illustrated in the picture shown below.

   

   An innovative way of enhancing the waterway’s riparian habitat is with the introduction of ‘habitat cells’ along Sungei Ulu Pandan (downstream of the iconic railway bridge). Habitat for biodiversity is improved with the additional greenery as well. More information on habitat cells can be found in Case Study 10.3: Sungei Ulu Pandan.

   Where there are space limitations, a full naturalisation of a waterway with bioengineering techniques like Kallang River @ Bishan-Ang Mo Kio Park is difficult to achieve. An option could be a partial naturalisation on one side of the waterway (where space permits). Naturalisation of the base of the waterway with rocks and/or planting will also improve the aesthetics of the waterway, particularly in waterways that are mainly dry. Hydraulic checks should be done to ensure that there is adequate capacity after taking these into consideration.

3. Creating a Permanent Waterbody

   Sometimes, there is little or no dry weather flow available in the canal. To provide a permanent pool of water in the waterway, weirs or dams can be constructed downstream to allow a buildup of water, thus creating a permanent waterbody in the waterway. This can help to improve the aesthetics and invite biodiversity into the waterway. The design of weirs or dams, however, has to take into consideration hydraulic and maintenance requirements.

4. Soil Bioengineering

   Soil bioengineering is a construction technique that harnesses the inherent qualities and capabilities of natural materials (plants, stones, branches, roots, etc.) for the purpose of providing structural integrity while being ecological and aesthetically pleasing. Soil bioengineering is typically employed in natural environments to stabilise a river embankment.

   In the context of enhancing waterways, soil bioengineering can be used to naturalise them. Soil bioengineering not only stabilises the slopes of the river bank, but also protects the slopes from erosion during storm events. The first of its kind in Singapore, the Kallang River @ Bishan-Ang Mo Kio Park project, is an example of a naturalised waterway completed in 2012.

   

   Some soil bioengineering techniques are “softer” in that they rely almost entirely on plant matter for their construction materials. These include techniques such as brush mattresses, fascines and geotextile with planting. Alternatively, there are “harder” soil bioengineering techniques, such as rip rap and gabion walls, which are predominantly constructed using rocks and come closer to traditional engineering.

   Application and Principles

   The suitability of specific techniques depends on site conditions such as the gradient of slope banks, soil type as well as the water velocity along the waterway. These would determine whether techniques that are more resilient are required. Professional soil bioengineering consultants should be engaged to provide an accurate assessment of the site conditions and to propose appropriate techniques. As soil bioengineered banks have higher roughness coefficient, hydraulic capacity of the waterways also need to be checked for compliance.

   Benefits

   Several benefits can be reaped from such soil bioengineering techniques. For example, soil bioengineering protects the soil surface from erosion caused by climatic elements (rain, wind) and increases soil integrity through establishing root networks. It also reduces the velocity of water flow, facilitates settlement and deposition of sand and silt, thus protecting the water quality of downstream waterbodies. In this way, soil fertility is enhanced through retention of nutrients. As soil bioengineering techniques employs only natural materials, it beautifies surrounding landscape and encourages habitat creation and promotes biodiversity.

   Operation and Maintenance

   As long as appropriate conditions for plant growth are maintained, soil bioengineering techniques are dynamically sustained, self-regulated and enhanced without the need for excessive maintenance. The deepening of the roots over time improves soil stabilisation and protects against erosion.

   Unlike hard structures, soil bioengineered waterways comprise live, dynamic and loose elements. Bedrock movements (e.g. stones and pebbles moved and carried along by high water velocity) and sedimentation (debris and silt generated from eroded rocks, plant damage and degeneration) are natural processes along the river. Periodically but infrequently, minor maintenance works (like replacement of displaced rocks, trimming of plants to prevent breakage, etc.) are necessary.

   Some of the routine maintenance requirements are as follows:

   • Litter and debris removal from the natural river channels and slopes

   • Removal of sediment accumulated at designated sedimentation basins

   • Maintenance of healthy vegetation growth. Regular care such as weeding, mowing, pruning and pest control is necessary.

   The naturalisation of waterways and waterbodies does not have to be limited to public projects or large developments. ABC Waters design features can be applied to a short segment of a canal that intersects or passes through a private development. Likewise, sections of an artificial pool or just small segments on one side of a canal bank can be naturalised to enhance the aesthetic, ecological and social value of adjacent developments.

1. Site Investigation

   During construction stage, site investigation works (especially soil property test and services detection) must be carried out before commencing physical works on site. Feedback should be given promptly if abnormalities or hindrances are observed during site investigation so that design can be reviewed early to suit site condition.

2. Site Coordination and Supervision

   Holding points in construction of ABC Waters design features are important and have to be carefully coordinated. Supervision by ABC Waters Professionals is needed at the following holding points:

   • Site Setting Out to prevent excessive excavation. For example, excessive excavation may lead to the need for safety railings (arising from a sharp drop) around the bioretention system due to proximity to pedestrian traffic.

   • Checking of catchment area to ensure that the catchment area designed to be treated is maintained during construction stage. This must be coordinated by the different disciplines: C&S, landscape architecture, architecture & ABC Waters works.

   • Leak test for geo-membrane liner (before the various soil layers are installed) if this is installed for the bioretention system.

   • Checking of materials used in the different layers of the ABC Waters design features before they are installed at site. Each batch of material delivered to site should be checked.

   • Inspection of each layer of the ABC Waters design features during installation. For example, in the installation of bioretention systems, the drainage layer, transition layer and filter media layer should always be supervised and inspected. It is a good practice to specify “holding points” for inspection after the subsoil pipes and each layer of soil media have been laid.

3. Implementation of Earth Control Measures (ECM)

   It is important to prevent silt and sediments from construction sites from flowing into the ABC Waters design features and the downstream drains during rain events, as these particles will clog up the filter media of bioretention systems. Silt and sediments from construction site shall be treated with ECM put in place. The specific requirements on ECM can be found in the Code of Practice on Surface Water Drainage.

   The following ECM shall be taken into consideration during the construction of ABC Waters design features:

   • When forming or excavating the profile of the ABC Waters design features;

   • After various soil layers are installed to prevent silt getting in to clog the layers;

   • Protection of ABC Waters design features shall continue until the bare areas on site have been stabilised.

   The ECM implemented on site shall be checked and maintained regularly to ensure that the ECM remains effective throughout the whole duration of works.

   

4. Construction Sequence

   Laying of various soil media is to be carried out immediately after the profile of the ABC Waters design features is formed or excavated. It is to prevent slope erosion as well as to prevent the excavated area from collecting water and becoming a potential mosquito breeding ground.

   No heavy vehicle movement is allowed within the ABC Waters design features after the profiles of the design features are formed. This is to prevent soil compaction which would inevitably affect the performance of the ABC Waters design features.

5. Workplace Safety and Health

   It is imperative that all construction projects adhere to the requirements stated in the Ministry of Manpower’s Workplace Safety & Health Act to ensure the safety of all employees, consultants, contractors and the general public during the site preparation, construction and site handover phases.

6. Mosquito and Pest Control

   The ABC Waters design features should be designed to prevent mosquito breeding by eliminating conditions that are favourable for mosquito breeding. These include:

   • the use of filter media with adequate permeability or hydraulic conductivity to prevent prolonged water stagnation,

   • keeping a constant flow through constructed wetlands and

   • avoiding the use of plants with receptacles or thick axils that can trap water.

   Notwithstanding the above, effective pest control measures should be adopted in construction sites and in completed premises as necessary to safeguard public health. The designer should also refer to the Code of Practice on Environmental Health, which addresses the various aspects of mosquito control.

1. Mosquito Control

   Efforts to prevent, detect, identify and destroy any mosquito breeding spots, as well as to eliminate potential habitats (places that could collect water or contain water stagnation) require the implementation of environmental management measures. These include:

   1. Routine surveillance (at least once a week) to eliminate potential habitats. This includes:

      • Ensuring proper drainage of places that could collect water or contain water stagnation

      • Removal of discarded items (litter, debris etc.)

      • Clearing of choked subsoil pipes or discharge outlets

      • Removal of plants with thick axils

   2. Regular monitoring and maintenance of subsoil drain pipes and sumps to ensure no water stagnation.

   3. Regular monitoring of the time taken for the detained runoff to infiltrate through the filter layer of bioretention systems. Prolonged detention times exceeding 1-2 days are likely to indicate clogging within the filter layer or subsoil pipes. As such, the following actions will need to be taken:

      • Flushing of subsoil pipes through the capped maintenance standpipes

      • Raking of the soil surface of the filter layer

      • Replanting of bare patches on the filter media.

   4. Introduction of fishes in surface flow wetland systems to aid in the control of mosquito larva.

   5. Engagement of a Pest Control Operator (PCO) to implement mosquito control programmes on-site.

2. Safety Audit

   The developer, consultants and external safety auditor shall conduct audit checks at the site to ensure that adequate safety measures have been put in place within the project site, and that water activities are carried out properly and safely (if applicable), and in accordance with safety procedures. Such audit checks shall take place periodically.

3. Public Education

   The following can be adopted to educate the public on the functions of the ABC Waters design features:

   • Signage

   • Workshops/educational programmes

   • Media (e.g. brochures/videos/websites)

4. Raising Awareness of Individual Responsibility

   While safety measures have been implemented, the public is encouraged to exercise individual responsibility and good sense when having fun near ABC Waters design features or at waterbodies. Where areas have been designated for water-play, parents shall educate their children on general safety measures. In general, the public should not enter any waterway as there may be swift currents due to a sudden surge of rapid water flow caused by a storm. For naturalised river like Kallang River @ Bishan-Ang Mo Kio Park, the public should observe all safety precautions when they enter the f loodplain of the river.

Like any system, maintenance is a necessary and important consideration, and sufficient provision shall be given to long-term maintenance during the design stage. The facilities and features must be monitored, inspected and maintained regularly to sustain their functions and benefits. Routine inspections and maintenance programmes also help to prolong the lifespan of these facilities and features. By detecting problems early, the maintenance cost can be reduced and any major repair or high replacement costs can also be avoided. Poor or irregular maintenance will result in system failure, additional expenses and adverse environmental impacts such as mosquito breeding, deterioration of water quality in downstream waterbodies, and flooding.

ABC Waters design features are green infrastructures that mimic natural systems. They are cost effective, sustainable, and environment friendly. These features harvest the natural cleansing capability of plants and soil to remove pollutants like nutrients and suspended solids without the need for sophisticated mechanical equipment and chemicals. As such, plant and soil (filter media) form the two main items for maintenance.

The following are key considerations to be taken into account when maintaining ABC Waters design features:

1. Landscape Maintenance

   ABC Waters design features (e.g. bioretention systems, vegetated swales, and wetlands, etc.) rely on the establishment of good vegetation to cleanse stormwater runoff. Vegetation also plays a key role in maintaining the permeability of the filter media of bioretention systems, while a uniform turf layer is important for vegetated swales to prevent scouring and soil erosion. Hence, ensuring adequate vegetation growth is a key maintenance objective as a healthy growth of vegetation is critical to the good performance of the systems. In the case of swales, overgrown vegetation is to be avoided as this may cause frictional force to rise sharply and greatly reduce the flow capacity of the swales.

   The most intensive period of maintenance is during the plant establishment period when replanting may be required. The use of fertilisers is to be restricted as far as possible. Replanting is necessary if there are bare patches on the f ilter media.

2. Maintenance of Bioretention Filter Layer

   The filtration of stormwater runoff through the filter layer is a key treatment process for bioretention systems. In addition to ensuring healthy vegetation growth to maintain the permeability of the filter layer, regular monitoring of the time taken for stormwater runoff to infiltrate through the filter layer shall be undertaken. Prolonged detention times exceeding 1-2 days are likely to indicate clogging within the filter layer or subsoil pipes. As such, the following actions will need to be taken:

   • Raking of the soil surface of the filter layer

   • Flushing of subsoil pipes through the capped maintenance standpipes

3. Cleaning Maintenance

   Routine cleaning maintenance for ABC Waters design features is essential, especially after a storm event, in order to clear any blockage to inlets, outlets and overflow points, and to remove litter and debris from the systems. Routine inspection to identify areas of sediment accumulation and to remove the sediments are necessary.

   Swales play an important role in the conveyance of stormwater runoff. It is important to inspect the swale profile to ensure that the swale has adequate conveyance capacity and a good slope so that there is no water stagnation hindrance to the conveyance of stormwater runoff.

4. Specific Checklists

   The major types of ABC Waters design features can be found in Section 4.2. The specific maintenance checklists are provided in the Engineering Procedures for ABC Waters Design features

5. Maintenance for ABC Waters design features used as detention measures

   ABC Waters design features such as bioretention basins, bioretention swales, sedimentation ponds, and wetlands can be utilised as detention measures for stormwater runoff, helping to regulate peak flow rates from developments.

   For these types of features, maintenance is crucial to ensure the designated detention volume is maintained. The developer must ensure that the maintenance agency maintains a high standard of upkeep for these ABC Waters design features upon their completion. Detailed maintenance requirements, as outlined in the maintenance checklists and drawings of the ABC Waters design features, will be shared in detail with the maintenance agency, along with necessary training.

   For more information, please refer to the videos on the maintenance for ABC Waters design features in the PUB website (https://www.pub.gov.sg/ Public/Places-of-Interest/Our-Reservoirs-and-Waterways/ABC-Waters/ Maintenance).

Under the ABC Waters Programme, Singapore’s waterways and reservoirs will be enhanced aesthetically, creating new community spaces to bring people closer to the water.

We hope that the community will enjoy these new spaces and forge a closer bond with water, ultimately becoming a Friend of Water. Friends of Water are made up of individuals and organisations that participate in PUB-organised activities, initiate water activities for their community or start their own initiative to educate the public. With more than 300 Friends of Water adopting ABC Waters sites, we hope more will continue to step forward as stewards of our waterways.

Public education is essential for ensuring responsible usage of public spaces. The 3P (People, Public, Private) sectors are encouraged to conduct educational activities in and around our waterways and waterbodies. ABC Waters Learning Trails utilise ABC Waters sites as experiential learning venues to educate the public on ABC Waters design features, river ecology, and the impact of their actions on our waterways and waterbodies.

Several schools have ABC Waters design features within their premises and utilise them for educational purposes across multiple platforms. For instance, West Grove Primary School’s Environment Club members learn about the multifunctional uses of the Rain Garden within their school during their sessions as part of their extracurricular activities. In collaboration with the National Parks Board (NParks), biodiversity surveys are conducted as part of NParks’ Community in Nature Initiative, Bioblitz, alongside volunteer scientists.

Rain gardens not only enhance biodiversity within the school grounds but also provide learning opportunities for students to better understand how natural materials such as soil media and plants can be used to cleanse stormwater runoff.

Ngee Ann Polytechnic partnered with the start-up Terraformers World for an ABC Waters Learning Trail at Sungei Tampines. Year 2 Diploma in Environmental & Water Technology (EWT) students took on the role of ABC Waters Learning Trail Guides for participants from the community. This event was part of EWT’s Year 2 ABC Waters Management module. The students shared how the use of natural materials in ABC Waters design features helps to improve water quality in our waterways and water bodies. EWT students also conducted an ABC Waters Learning Trail at Jurong Eco-Garden, an ABC Waters certified project as part of the Jurong Community Festival.

PUB collaborates with and empowers community partners to develop their own programmes at ABC Waters projects. As part of Singapore World Water Day 2023, Tanjong Katong Girls’ School developed and conducted guided community learning trails along Geylang River. Educational materials were made available to the public via QR codes. Geylang River, one of Singapore’s oldest rivers, was transformed and revitalised under the ABC Waters programme in 2014, with design elements reflecting the area’s past heritage as a Malay settlement. Students from Kong Hwa School and Geylang Methodist School (Primary) enjoyed the learning journey and learned about the importance of water sustainability.

PUB recognises the importance of actively engaging the community in the ABC Waters Programme. One of the key aims of the programme is to ensure community ownership of the water assets upon completion. The projects are customised to meet the public’s needs through community consultation during the early conceptualisation stages.

ABC Waters @ Sungei Tampines was officially opened in 2023. Drainage improvements, along with ABC Waters enhancements, provide the residents of Tampines with improved infrastructure and a beautiful blue-green environment. ABC Waters features such as naturalised canal banks, rain gardens, and lookout decks have been incorporated to enhance overall livability and create vibrant community spaces. To encourage community appreciation, Tampines North Grassroots Organisations (GROs) organised a National Day celebration with fun f illed carnival programmes and activities along the banks of Sungei Tampines.

Tampines North GROs will continue to organise more events for residents to bond and enjoy the beautiful communal space. This includes a Mid-Autumn Festival where families can participate and bond during the lantern procession along Sungei Tampines.

This is in addition to the many regular activities that residents of Kolam Ayer have been enjoying along the waterway at the Kolam Ayer ABC Waterfront, with the CCC organising festive celebrations on the deck and the annual kayaking expedition as part of the Singapore World Water Day celebrations.

Private sectors have also taken ground-up initiative to promote ABC Waters Programme. One of them is Systems on Silicon Manufacturing Company Pte. Ltd. (SSMC) who have plans to educate the community on the importance of keeping our catchment and waterways clean. They have started training staff volunteer docents for Lorong Halus Wetlands Learning Trail since 2023. So far, about 40 SSMC employees have completed the training and can lead future guided tours.

The ABC Waters Programme calls on the efforts of the public to keep our waters clean. Under the Programme, well used community spaces are created where the waters integrate seamlessly with the surrounding landscape. Hence, PUB encourages private developers and landowners to incorporate waterways into their developments and implement ABC Waters design features which will contribute to a beautiful, clean and green living environment.

With applications open throughout the year, developers of completed projects or projects that have the detailed design finalised are encouraged to apply for ABC Waters Certification, which is valid for three years. Evaluation and assessment of the projects is conducted based on the information and declaration submitted in the application form. For completed projects, site checks will be carried out to verify the information given in the application documents.

For projects before completion, applicants are to ensure that the information provided is accurate and up-to-date. Site checks will be conducted during the Temporary Occupancy Permit (TOP) stage to verify that the certified projects are executed in accordance to the design declared in the application documents.

Under this scheme, public agencies and private developers of the ABC Waters certified projects are allowed to make use of the ABC Waters logo to promote their developments as ABC Waters-certified.

The ABC Waters Certification application form can be downloaded from https://www.pub.gov.sg/Professionals/Awards-and-Certification/ABC-Waters-Certification. Projects that have received ABC Waters certification are publicised on the same website.

PUB launched the ABC Waters Certification on 1 July 2010 to provide recognition to public agencies and private developers who embrace the ABC Waters concept, and incorporate ABC Waters design features in their developments.

The ABC Waters Certification Scheme is evaluated based on four categories – Active, Beautiful, Clean and Innovation.

For a project to be certified, it needs to receive a minimum of 45 points, with at least 5 points in each of the first 3 categories.

In August 2017, a higher tier of certification, ABC Waters Certified (Gold), was launched to recognise entries of exceptional standards.

For a project to be ABC Waters Certified (Gold), the project needs to attain a minimum of 65 points, with at least 5 points from the Active and Beautiful categories. Under the Clean category, treatment of surface runoff from at least 40% of the total site area must be attained through the use of ABC Waters design features.

Projects which attain ABC Waters Certified (Gold) are also entitled an additional score point in the certification for BCA Green Mark for New Residential Buildings 2016 (GM RB: 2016).

Under BCA Green Mark Certification’s Resilience Innovation Guidance Notes: RE 1 Protect, where projects incorporate Active, Beautiful, and Clean Waters (ABC Waters) design features for sustainable stormwater management to maintain the quality of water in waterways and reservoirs and enhance biodiversity and the living environment. Projects that attain PUB’s ABC Waters certification can be considered for points under Innovation.

Active Category

This section aims to encourage vibrancy and activity at each site by providing new community spaces for people to enjoy recreational activities. This will bring people closer to water.

Beautiful Category

This section focuses on achieving integration between water and greenery to achieve scenic waterscapes which enhances the aesthetics and biodiversity of the site.

Clean Category

This section focuses on sustainable and holistic stormwater management through the adoption of ABC Waters design.

Innovation Category

This section recognises creativity and innovation in incorporating ABC Waters design or other environment-friendly features to minimise the impact of urbanisation on the quality and quantity of stormwater runoff. It also acknowledges exemplary designs that go beyond the standard criteria listed in the ABC Waters Certification Scheme.

Recognising the importance of developing the industry’s competence to bring the ABC Waters design concept to fruition, PUB collaborated with the Institution of Engineers Singapore (IES) to launch the ABC Waters Professional Programme with the support of the Singapore Institute of Architects (SIA), Singapore Institute of Landscape Architects (SILA), HDB, LTA and NParks in 2011. The programme, comprising of 4 core modules and 5 elective modules, aims to equip industry professionals with the necessary expertise in various aspects of ABC Waters design features from design to construction and maintenance. The 4 core modules are:

1. Understanding ABC Waters Design Guidelines and Certification

2. Stormwater Quality Management – Planning and Designing ABC Waters Design Features

3. Design, Construction and Maintenance of Swales and Buffer Strips

4. Design, Construction and Maintenance of Bioretention Basins and Bioretention Swales

More information on the ABC Waters Professional Programme can be found at the following link: https://www.ies.org.sg/Registries/ABC-Waters-ProfessionalRegistry.

Following the introduction of the ABC Waters Professional Programme, the ABC Waters Professional Registry was launched in May 2013. Professionals who have successfully completed all 4 core modules and 2 elective modules of the ABC Waters Professional Programme are eligible to be registered as an ABC Waters Professional with IES, SIA or SILA, if they also meet the registration criteria of the respective professional bodies. The Registry aims to enable the industry to recognise the quality design work of ABC Waters Professionals.

Workshops, seminars and talks related to the ABC Waters design and case studies are conducted regularly to keep ABC Waters Professionals abreast on innovative designs and ideas adopted in ABC Waters design features to achieve sustainable stormwater management.

As of Apr 2024, there is a pool of more than 120 registered ABC Waters Professionals in the industry (including Professional Engineers, Professional Architects and Accredited Landscape Architects) to carry out work on ABC Waters design features.

The developer/owner shall engage ABC Waters Professionals to plan, design, oversee construction, and develop a maintenance plan for ABC Waters design features.

For developments exceeding 0.4 hectares, Development Control (DC) submissions for ABC Waters design features shall include the following items to be submitted to the Board as part of the DC submission:

1. Hydraulic calculations for the ABC Waters design features, endorsed by an ABC Waters Professional who is a registered Professional Engineer (Civil). The calculation shall be accompanied by completed relevant design templates in Excel format, available on the PUB website.

2. Catchment/location plan of ABC Waters design features endorsed by an ABC Waters Professional who is an Accredited Landscape Architect or a registered Professional Architect.

3. Design drawings and maintenance checklists endorsed by an ABC Waters Professional of any relevant profession.

If there is any change to the catchment or design of the ABC Waters design features post-DC approval, the Qualified Person (QP) shall submit a DC amendment with the full set of updated items 1, 2 and 3 above with the respective endorsements and a summary table of all the amendments.

When ABC Waters design features are utilised for detention purposes to meet peak runoff reduction requirements, an ABC Waters Professional shall inspect these features at the Temporary Occupation Permit (TOP) stage. This inspection ensures that the features are functional and constructed according to their designed detention volume.

The ABC Waters professional should also ensure that the maintenance checklist is handed over to the relevant maintenance agent. This step ensures that the features will be maintained to the required detention volume capacity.

The Drainage Handbook on Managing Urban Runoff was jointly developed by PUB and IES. Launched in May 2013 and subsequently updated in 2024, this book serves as a valuable resource for developers, architects, and engineers. It provides an in-depth understanding of the holistic Source-Pathway-Receptor approach to stormwater management, focusing on the technical considerations of “Source,” “Pathway,” and “Receptor” measures.

The handbook covers various concepts and case studies of on-site stormwater management and flood protection practices. It also includes information on ABC Waters design features and structural detention and retention measures that can be adopted to ease surface runoff and reduce peak flow of stormwater into the public drainage system. The updated version offers enhanced insights on the “Pathway” aspect and presents more recent and local examples for each of the three measures. ABC Waters Professionals can use this guidebook as a reference when integrating ABC Waters design features with other drainage elements such as detention tanks

Average Recurrence Interval (ARI)

An estimated time period between storm events of a given magnitude. Typical ARIs include 1 in 25 years, 1 in 10 years and 1 in 3 months.

Biodiversity

Biodiversity is the variation of life forms within a given ecosystem, biome, or for the entire Earth. Biodiversity is often used as a measurement of the health of biological systems.

Catchment

An area of land from which stormwater flows to a common point, usually ending in a river or canal, and eventually a reservoir or the sea.

Ecology

Ecology is the scientific study of the distribution and abundance of life and the interactions between organisms and their natural environment.

An ecosystem is a natural unit consisting of all plants, animals and microorganisms (biotic factors) in an area functioning together with all of the non-living physical (abiotic) factors of the environment.

Floodplain

The flat, or nearly flat area adjacent to a waterway that is designed to be inundated during a heavy storm.

Nutrients

These are substances that promote growth of plant and algae such as nitrogen and phosphorus. Excessive nutrients in waterways contribute to algal blooms and degrade our waterways.

Plot Ratio

The ratio of the gross floor area of the building(s) in a development to its site area.

Pollutants

Substances that may naturally occur but are present at harmful levels (e.g. sediment or nutrients in a waterbody) or which may be unnatural in the environment and capable of producing environmental harm (e.g. chlorinated pesticides).

Receiving Water

This is a waterbody that may receive runoff from the catchment area, and generally has some environmental value or beneficial use. Natural wetlands are included in the definition of receiving waters, as opposed to constructed wetlands that have been built primarily for the purpose of stormwater treatment.

Treatment Train

A series of stormwater treatment devices that collectively address all stormwater pollutants.

Sediment

Particulate matter such as sand or mud that is generally derived from the lands and can be suspended and transported by fluid flow.

Scouring

Erosion caused by flowing water.

Site Area

The area of a development plot measured between the survey boundary lines. The boundary line defines the legal ownership of the property or development site.

Stormwater Runoff

Surface water runoff following a rain event, which includes piped flows from catchment surfaces such as roads, pavements, rooftops, carparks, vegetated area and open space.

Urban Development

Non-rural development forms such as rural-residential, suburban and dense urban, which includes residential, commercial, and non-rural industrial areas. Urban development forms could comprise greenfield, redevelopment, infill and retrofit of urban built infrastructure.

Water Quality

Physical, chemical, biological and radiological characteristics of water. It is a measure of the condition of water relative to the requirements of one or more biotic species and/or to any human need or purpose.

It is important that all designs and implementations comply with the various building and planning authorities’ regulations. The following is a suggested list:

Building & Construction Authority (BCA)

• http://www.corenet.gov.sg/einfo/

• http://www.bca.gov.sg/GreenMark/green_mark_projects.html (Green Mark Awards)

• http://www.bca.gov.sg/BarrierFree/barrierfree_buildings.html (BCA Code of Accessibility)

Housing & Development Board (HDB)

• http://www.hdb.gov.sg/

Land Transport Authority (LTA)

• http://www.lta.gov.sg

• http://www.lta.gov.sg/content/ltaweb/en/industry-matters/development-and building-and-construction-and-utility-works.html

  (Development, Building, Construction & Utility Works)

Ministry of Manpower (MOM)

• http://www.mom.gov.sg

• http://www.mom.gov.sg/workplace-safety-health/wsh-regulatory-framework (WSHA - Workplace Safety & Health Act)

National Parks Board (NParks)

• http://www.nparks.gov.sg

• http://www.nparks.gov.sg/cms/index.php?option=com_content&view=article &id=36&Itemid=150 (Development Plan submission requirements)

Urban Redevelopment Authority (URA)

• http://www.ura.gov.sg

• http://www.ura.gov.sg/uol/publications/technical/dc-handbooks.aspx

  (Development Control Handbooks)

• http://www.ura.gov.sg/uol/circulars/2009/apr/Iushprogramme.aspx

  (Circular Package: LUSH Programme - Landscaping for Urban Spaces and High Rises Programme)

• http://www.ura.gov.sg/uol/circulars.aspx

  (Circulars)

National Environment Agency (NEA)

• https://www.nea.gov.sg/docs/default-source/resource/practices-/copeh-2021.pdf

  (Code of Practice on Environmental Health)

The following provides detailed information regarding the implementation of ABC Waters design features:

Engineering Procedures for ABC Waters Design Features

• Engineering Procedures for ABC Waters Design Features gives specific guidance on selection and sizing of the features, computational procedures with worked examples, performance charts to develop the detailed designs and checklists for construction and maintenance.

• https://www.pub.gov.sg/-/media/PUB/Reservoirs/ABC/PDF/CondensedBooklet_of_Engin_Procedures.pdf

Code of Practice on Surface Water Drainage

• https://www.pub.gov.sg/Professionals/Resources/Code-of-Practices

Drainage Design Handbook on Managing Urban Runoff

• https://www.pub.gov.sg/-/media/PUB/PDF/managingUrbanRunoff.pdf

The following are additional resources:

A Selection of Plants for Bioretention Systems in the Tropics

• https://www.cuge.com.sg/research/download.php?product=47

Sustainable Landscape

• https://www.cuge.com.sg/landscapeservices/main/landscape-weed-mgmt and-sustainable-landscape-e-book.html

Concept Design Guidelines for Water Sensitive Urban Design (Southeast Queensland, Australia)

• http://www.waterbydesign.com.au/conceptguide

Adoption Guidelines for Stormwater Biofiltration Systems (Corporative Research Centres Programme for Water Sensitive Cities, Australia)

Green Roofs and Heat Island Effect (United States Environmental and Protection Agency)

• http://www.epa.gov/heatisland/mitigation/greenroofs.htm

A Selection of Plants for Waterways and Waterbodies in the Tropics (Jean W.H. Yong, Tan Puay Yok, Nor Hafiz Hassan, Tan Swee Ngin)

Sungei Tampines is a 3.3 km-long waterway leading to the sea that runs through the housing estates of Tampines and Pasir Ris. It serves a catchment area of 919 ha which includes Tampines Eco Green Park and Pasir Ris Park. In 2015, a 1.1 km stretch of the canal between the Tampines Expressway (TPE) and Pasir Ris Drive 3 received a makeover, under National Water Agency PUB’s Active, Beautiful, Clean Waters (ABC Waters) programme. Enhancements such as new community spaces along the waterway and rain gardens were introduced to educate the public and improve water quality.

In 2018, a 1.4 km upstream section of Sungei Tampines from Tampines Avenue 7 to TPE was identified for upgrading to serve new HDB estates in Tampines North. Works began in May 2018 and were completed in July 2022.

As part of this drainage improvement project, PUB also introduced new features along the waterway to enhance overall liveability. Under the makeover, PUB transformed a concrete canal into a naturalised river, constructed new recreation and community spaces for residents and enhanced the area’s connectivity to Tampines Eco Green.

Sungei Tampines is the first PUB project to include an extensive stretch of naturalisation (about 1 km) along one bank of the canal (at Tampines Eco Green), using soil bioengineering techniques similar to Kallang River – Bishan-Ang Mo Kio Park, and greening at the canal base. The other bank is integrated seamlessly with a concrete cantilevered park connector adjacent to the nearby housing estates, along with lookout decks to bring the public closer to the waterway. Together with ABC Waters enhancements such as rain gardens and greening of the canal walls, these features have created a vibrant and liveable space for all to enjoy.

Key Features

Naturalised Riverbank

The naturalised riverbank along Sungei Tampines is constructed using soil bioengineering materials. Plants on the slope were selected for slope stabilisation as well as to foster a robust, native riparian habitat for biodiversity.

Plants and shrubs were planted at various sections on the base of the canal, with island planters along the meandering dry weather flow. The greenery helps to soften the concrete hardscape.

Rain Gardens

There are three rain garden nodes along Sungei Tampines - designed to detain and cleanse stormwater runoff from Tampines Eco Green and the surrounding areas before it is discharged into the river. The rain gardens also provide a conducive habitat for a wide range of flora and fauna to foster rich local biodiversity.

Lookout Decks

Residents can now enjoy newly added recreational spaces such as the lookout decks that are provided on the northern bank adjacent to Tampines Eco Green and are sited strategically to conceal and integrate the sewer line that runs beneath the naturalised riverbank into the reconstructed canal.

In addition, new seats and shelters have been constructed, while existing ones were refurbished to provide residents with a better view of the scenic waterway. Additional shrubs along the riverbanks and new footpaths were also added to enhance the experience for park users and encourage residents to spend time by the waterway to enjoy the blue-green corridor that runs through their housing estate.

The existing crossing (Garden Link) next to TPE was re-constructed with additional plantings, to enhance the experience of residents. In addition, a new bridge (Garden bridge) was constructed near Block 496C to provide additional connectivity for residents travelling between the housing estate and Tampines Eco Green.

Jointly developed by PUB and HDB, the new Alkaff Lake demonstrates PUB’s approach to manage flood risks in land-constrained Singapore – a multifunctional solution that improves flood resilience and provides new recreational spaces.

Managing storm water and improving flood resilience

Integrated within the 10-hectare Bidadari Park, Alkaff Lake serves as a retention pond that slows down and reduces stormwater runoff during a heavy storm, taking pressure off the downstream public drainage system and thus reducing the risks of flash floods.

Alkaff Lake is a “pathway” solution under PUB’s holistic “Source-Pathway-Receptor” approach to manage storm water, which introduces adaptability and flexibility to Singapore’s drainage system when looking at solutions for flood protection.

This is the first project since Kallang River at Bishan-Ang Mo Kio Park with multifunctional blue-green space. On dry days, the lake’s banks are used for recreational activities; on rainy days, water levels will rise within the banks of the lake for temporary storage of stormwater.

Peaceful green spaces for the community

Alkaff Lake is integrated seamlessly with Bidadari Park, along with a nest-shaped deck with panoramic views of the park, to provide additional recreational spaces for the community, as well an island in the middle of the lake where a conserved rain tree stands. Active, Beautiful, Clean Waters (ABC Waters) features, such as the terraced wetlands and cascading creek, help to cleanse stormwater runoff, before discharging into the lake.

Members of the public can enjoy the scenic surrounds of Alkaff Lake with peace of mind. Water level sensors in the lake trigger a warning system when it rains, with public announcements and warning lights to alert the public to move out of the lake.

Built in 1977, the 2.5 km long Sungei Ulu Pandan stretches from Clementi Road to Ayer Rajah Expressway (AYE). The canal’s upstream portion (about 600 m) was enhanced under PUB’s ABC Waters Programme in 2013, creating Singapore’s f irst river-side classroom where residents and students from nearby schools can learn more about our waterways and the ABC Waters design features (e.g. rain gardens, vegetated swales) that were added.

Works to improve the remaining 1.9 km stretch were completed by PUB in 2022. The existing canal, with its concrete channel and turfed banks, has been enhanced further with a wider plant palette along the riverbanks and the addition of “habitat cells” at five locations. Habitat cells consist of a shallow stream with riverine planting carved within existing riverbanks which are located away from the main f low of the waterway and provide nesting spots and shelter for various fauna species. These were constructed using soil bio-engineering techniques to retrofit an existing manmade waterway. A rain garden and vegetated swales were also implemented along the riverbanks to cleanse stormwater runoff before it enters the waterway.

Habitat Cells

The project objective was to tap on the potential of the existing waterway and natural greenery in the area to create a rich, biodiverse riverine corridor along the canal using habitat cells, which are shallow streams with riverine planting along its banks. Located at the edge of the riverbanks away from the canal’s main f low, they provide nesting spots, shelter and food source for waterfowl and other fauna. This is the first time PUB is implementing such features along a waterway.

Lookout decks were also built at strategic locations to provide vantage points overlooking the habitat cells, allowing public to observe the flora and fauna up close.

A baseline biodiversity survey was carried out in May 2018 to identify the existing riparian fauna communities, which guided the design of the project to minimise disturbances to a potential otter holt as well as areas that serve as habitats for woodland-dependent species such as the endangered Changeable Hawk-Eagle and the critically endangered Grey-headed Fish Eagle.

PUB worked closely with NParks and the Nature Society (Singapore) to ensure that the project was implemented in a sensitive manner. The results of the study, together with the feedback received, influenced the final location of the lookout decks and habitat cells. Plant species were also selected to attract butterflies, bees, small birds and waterfowl as well.

Jurong Lake, one of Singapore’s 17 freshwater catchment reservoirs, was formed by the damming of Sungei Jurong and is an important source of Singapore’s water supply.

Nestled within Jurong Lake Gardens, Singapore’s first national garden in the heartlands opened by the National Parks Board (NParks), Jurong Lake has been transformed under PUB’s Active, Beautiful, Clean Waters (ABC Waters) programme into a venue for recreation and community bonding to bring people closer to the water.

Completed in July 2021 by PUB, the ABC Waters project at Jurong Lake introduced new floating boardwalks and wetlands along the northern shore of Jurong Lake to provide communal spaces for the public to enjoy scenic views of the lake and get up close to the flora and fauna thriving on the floating wetlands.

Floating Wetlands

With an area of 3,850 m2, the floating wetland at Jurong Lake is the largest man made floating wetland system in Singapore to date. Other floating wetlands can be found at Punggol Reservoir (Sengkang Floating Wetland next to Anchorvale Community Club) and Pang Sua Pond (next to Senja-Cashew Community Club).

The floating wetlands at Jurong Lake is an engineered system with plants growing on a floating mat on the surface of the water. Rooted emergent (i.e. plants that grow in water with leaves and f lowers above the water) are selected for planting on the floating wetland. The uptake of nutrients by the plants on the f loating wetland reduces nutrients in the water; this helps to minimise excessive algal growth. The plants’ roots also serve as a natural environment (or substrate) for the growth of a community of microorganisms that breaks down organic pollutants in the water.

This makes floating wetlands a low energy and self-sustaining treatment feature as sunlight, plants and microorganisms are the main active agents in treatment processes. In addition, plants help to beautify the environment and enhance the biodiversity of natural habitats.

Various wildlife have been observed making themselves at home in and around the floating wetlands, including grey herons, egrets, kingfishers, waterhens, monitor lizards, bees, butterflies, dragonflies and damselflies, as well as the iconic smooth coated otter.

The Keppel Marina East Desalination Plant (KMEDP) is an ABC Waters Certified (Gold) project. Managed by Keppel, KMEDP is designed to produce potable water by treating either seawater or reservoir water depending on the prevailing weather conditions. Using reverse osmosis, the desalination plant can produce 30 million gallons of drinking water per day. KMEDP is the first large-scale, dual mode desalination plant with an extensive landscape and ABC Waters design features. The iconic large green roof and cascading water feature are opened to public, promoting public recreation.

The project has an integrated sustainable stormwater management system, where stormwater runoff from the large green roof (65 % of the total site area) f lows into three bioretention basins (rain gardens) for treatment and later collects in a rainwater harvesting pond to be recycled in a cascading water feature as well as used for irrigation.

Bioretention Basins and Rainwater Harvesting Pond

The bioretention basins receive runoff from the green roof, detains, treats and discharges the rainwater at a reduced flow rate, into the detention tank. Butterflies and bird-attracting native plant species are proposed on the rooftop bio-retention basins to connect and integrate with the pollination garden along the promenade, hence improving the overall aesthetics of the development.

The rainwater harvesting pond acts as a retention and detention pond and is designed as a natural-looking pond containing native aquatic plants in planter boxes, on the edge of the pond along the promenade, as well as inside the pond. This rainwater harvesting system blends in nicely with the surrounding lush green environment, and water features.

Cascading Water Features

The cascading water features are an aesthetic element in the development with circulated water from the harvesting pond.

Green Roof

The iconic rooftop of KMEDP is covered with 1.96 ha green lawn dotted with trees and surrounded by bioretention basins. The green roof functions as an activity lawn for various recreational activities. Users can rest on sheltered seatings provided on the lawn or non-sheltered seatings provided along the perimeter walkway.

Developed by Housing and Development Board, Rivervale Shores is an ABC Waters Certified (Gold) project that showcases an extensive array of biophilic water features, lush landscape comprising e-deck, intensive/ extensive green roofs, vertical greenery, sky terraces, aesthetic features like water-walls and a staircase integrated with a rock garden. Overlooking the Serangoon Reservoir, the 10-hectare public housing precinct is seamlessly integrated with the reservoir’s waterfront. The precinct is also easily accessible via Sungei Serangoon park connector and an overhead bridge that links a park across the precinct.

The development features a network of environmentally sustainable ABC Waters Design Features such as bioretention basins (rain gardens) and bioretention lawn. These were designed to detain and treat runoff from 51% of the total site area with the use of plants and layers of soil filters, before discharging cleansed runoff into the Serangoon Reservoir. Facilities like the precinct pavilion, an outdoor refreshment area, sheltered walkway, footpath, decks, fitness facilities, playgrounds are located near the ABC Waters design features to bring people closer to the water.

Rain Gardens

Spreading across 7 clusters within the precinct, there are 24 bioretention basins integrated with various landscape features. The bioretention basins incorporate features that allow residents to appreciate the flow of stormwater and its treatment. Attractive features such as fish sculptures, water-wall and boulders (part of a grand staircase) create a distinct experience for these ABC Waters design features.

Bioretention Lawn

The bioretention lawn is a type of bioretention basin that serves as a water collection area in the event of rain, while offering an open space for outdoor recreational activities during dry weather.

Landscape Deck, Extensive and Intensive Green Roofs

Vertical greenery is implemented throughout the landscape deck’s perimeter and sky terraces, providing a more pleasant living environment for residents.

The extensive green roofs help to slow down runoff and create habitats for micro biodiversity. They are non-accessible to the public and contain plants of less than 300 mm high. Besides slowing down runoff and adding aesthetic appeal, the extensive green roofs will also lower the building’s temperature. On the other hand, the intensive green roofs which contain plants of about 300 to 500 mm high, are accessible to the public. They are equipped with auto irrigation system supplied with treated stormwater from one of the rain gardens, to water the plants.

Situated in the heart of the new Bidadari estate, The Woodleigh Mall and The Woodleigh Residences is an ABC Waters certified (Gold) mixed-use development comprising of a shopping mall and private residential flats easily accessible via Woodleigh MRT station and Bidadari Park. Jointly developed by Kajima Development Pte Ltd and Cuscaden Peak Investments Pte Ltd, the project is designed to be contemporary and timeless, offering residents and the public a sense of tranquility and serenity by integrating the communal and lifestyle facilities with a myriad of green spaces.

ABC Waters design features such as bioretention basins (rain gardens) were built to treat stormwater runoff as well as enhance the aesthetic value of the area. By decentralising the rain gardens and locating them close to source, treatment of surface runoff from 51 % of the site area is made possible. A wide selection of plant species was planted in the rain gardens to attract birds and butterflies, improving biodiversity.

Rain Gardens

More than 80 rain gardens of varying sizes are well distributed throughout the landscape deck at level 3 in The Woodleigh Residences. They are situated alongside circulation footpaths and communal facilities to enhance the proximity between residents and these rain gardens.

Extensive Landscape Deck at Level 3

Decorated with a lawn and themed gardens, vertical greeneries are provided to add lushness and enhance the living environment of the residents. The Green Bridge is part of the L3 landscape deck with facilities. Part of the area at the end of Bridge at L2 is accessible by the public and serves as a vantage point to the adjacent Bidadari Park and scenic Alkaff Lake.

The landscape design concept of The Woodleigh Residence encompasses Japanese design elements like Shizen (Naturalness), Seijaku (Tranquility) and Miyabi (Elegance) to seamlessly connect nature with the community and individuals to achieve the overarching concept of Wa (Harmony) which symbolises the ethos of unity between man and the natural environment.

Developed by Housing and Development Board, Garden Terrace @ Tengah is an ABC Waters Certified (Gold) project that will be located within the Garden District in Tengah Town. Taking inspiration from garden elements, roof gardens located at different heights in the development will step down towards the common green. The development has a total site area of 3.26 hectares with 16 bioretention basins (rain gardens) and 1 vegetated swale that will treat runoff from about 53 % of the entire site area. Lush greeneries planted in the development comprising 51.5 % native species will enhance biodiversity.

Rain gardens and vegetated swales will be located near well-frequented amenities like drop-off porches, sheltered walkways, playgrounds, fitness stations, childcare centre and community living space. The ABC Waters design features are part of HDB’s Eco initiatives. The features could form part of children’s learning in helping them to appreciate nature and water as an asset.

ABC Waters design features and Native Plants

16 rain gardens and one vegetated swale will be distributed throughout the development treating runoff from roof, ground hardscape and ground softscape areas in their vicinity. These ABC Waters design features are strategically located so that residents and visitors will be able to see them in both wet and dry conditions. The precinct will be planted with more than 50 % native species that are essential to preserve biodiversity and create healthy ecosystems.

Roof Gardens

An intensive (accessible) roof garden will be located on the Multi-story Carpark and an extensive green roof (non-accessible) will be located on the childcare centre. Accessible sky terraces will also be provided in 3 residential blocks. They help to slow down roof runoff, provide community space and temperature control for the blocks as well as architectural aesthetic enhancement to the surrounding area.

Rainwater Harvesting Tank

Treated stormwater from three rain gardens and the vegetated swale will be channeled to the underground rainwater harvesting tank. It will be further treated by mechanical filtration system before storage and reuse for general cleaning and landscape irrigation.

Located in the heart of Punggol Digital District, Singapore Institute of Technology (SIT) Campus @ Punggol North is the first of its kind to be designed as a “Campus-in-the-Park”, aptly complementing the campus’ location by the Punggol Waterway Park and Serangoon Reservoir. The campus is divided into East and West zones and is estimated to be completed by 2024. This is an ABC Waters Certified (Gold) project.

10.8.1 SIT Campus @ Punggol North (East Zone)

The east zone of the SIT Campus is dubbed as the “Campus Court”.

Campus Court was designed with the concept of a courtyard in mind — to create a fluid learning and campus experience, through the inclusion of many big and small courtyards, with hard and soft landscapes. Connectivity facilities such as the pedestrian bridge and boardwalk across various forms of landscape and ABC Waters design features enhance the collective user experience. Furthermore, the walkway, viewing decks and seats along the fringe of pond and the Terrace Court along Serangoon Reservoir are easily accessible, bringing people closer to the water. The Campus Court features a bioretention basin (rain garden), a two-tier cleansing biotope and a sedimentation pond, treating 40% of the entire site runoff.

Sedimentation Pond

The sedimentation pond, which has a permanent water area of 689 m2, supplements the detention tank located at the first storey to fulfill the site’s detention requirement by functioning as a stormwater detention pond. It collects runoff from upstream ABC Waters design features such as the vegetated swales and cleansing biotope within its extended temporary ponding. Overflow from the rainwater harvesting tank is also detained in the pond, where runoff is discharged to the drains at a controlled rate.

Rain Garden

Besides treating stormwater runoff, the bioretention basin has an extended drainage layer thickness of 1200 mm which allows it to temporarily detain runoff. This helps to fulfill the site’s detention requirement by reducing peak flow of runoff into the drainage system during rain events.

Green Features Around Campus Court

Extensive green features integrated across the campus are designed according to the architectural limits and loading capacity of each building to enhance the overall aesthetics and thermal comfort of the campus. Multiple sky terrace gardens located across different floors of the campus building provide functional shading and cooling. Moreover, the use the different native and ornamental plants in the gardens provide an immersive delightful experience with scent, colours and shades for students and staff. Communal roof-top sky gardens at the 2nd, 10th and roof level are elaborate with the inclusion of paved-pathways, lighting fixtures and benches to create accessibility and promote recreational usage among students and staff.

10.8.2 SIT Campus @ Punggol North (West Zone)

Known as the “Campus Heart”, the west zone of the SIT Campus is uniquely endowed with an existing secondary forest. The design leverages on this green site asset by seamlessly integrating its learning environments with biophilic indoor-outdoor spaces. SIT’s Campus Heart houses the library, academic buildings, a sheltered event plaza, an open Campus green and the Hatchery building. The Campus Heart features three bioretention basins (rain gardens) and a single tier cleansing biotope, treating 43% of the entire site runoff.

Bioretention Basins

Bioretention basins are located at each of the three sub-plots, collectively detain and treat runoff from 40% of the 4.8-hectare site. The treated runoff then flows downstream respectively to the three rainwater harvesting tanks where it is stored for non-potable use such as irrigation. Barrier-free pedestrian walkways and garden paths erected near to the bioretention basin maximises connectivity and accessibility to the water so that students and staff can enjoy the features up close.

Cleansing Biotope and Eco-pond

The cleansing biotope located at the ground floor of the campus treats stormwater runoff and discharges to the eco-pond. A recirculation system pumps water from the eco-pond to the cleansing biotope, which provides natural treatment of the runoff and helps to maintain good water quality throughout the entire pond. Granolithic steps built around the eco-pond provide places for students and staff to sit near the water feature for those who wish to appreciate the water feature up close.

Soilless Green Roof, Vertical Greenery, Sky Garden, and Garden Courtyard

Sustainable green features such as green roofs, vertical greenery, sky gardens and garden courtyards are implemented all around the architectural façade within the SIT Campus to promote green connectivity and provide a more pleasant internal environment. These features aid in providing thermal comfort and reducing energy costs by absorbing heat generated by the external surroundings. 37% of the plants used in the design features that embellish the whole campus are native plant species, which is integral to promoting biodiversity.

Rainwater Harvesting Tanks

Overflow from the bioretention basins will be channeled into the respective rainwater harvesting tanks and stored for non-potable reuse such as irrigation, general washing, etc. These tanks are designed to reduce potable water use. Automatic drip irrigation systems are used to irrigate the landscape across the campus buildings.

The 9-hectares Yunnan Garden Rejuvenation project located in the Nanyang Technological University (NTU) Main Campus is an ABC Waters Certified (Gold) project. Being a major historical landmark of the Nanyang University in the mid 1900s, Yunnan Garden housed two of the national monuments, namely the Chinese Heritage Centre and the Nanyang University Memorial.

This project adopted a water sensitive approach for the landscape design by implementing a treatment train of ABC Waters design features into the landscape. The challenging topography of the site was turned into a series of water bodies with cascades, and the different segments of the water body consisted of a sedimentation basin, Nanyang Lake, Recreational Pond, a series of constructed wetlands and Yunnan Garden Wetlands. In between, ABC Waters design features such as the rain gardens and the cleansing biotopes, as well as a waterfall were integrated with the thematic gardens as part of the treatment train. The treatment train can treat runoff from 70.4 % of the total site area. These naturistic elements integrate indistinctively and sensitively with the manmade structures, creating a pleasant environment for students to reside in. The project also features an elevated boardwalk and walkway promenade to bring people closer to the ABC Waters design features and enjoy the landscape at different viewpoints.

Sedimentation Basin

The sedimentation basin was constructed to solve the high-water table and ponding issues prior to the Yunnan Garden Rejuvenation project. It is located upstream of the treatment train, retaining course to medium sized sediments before discharging the runoff into the constructed wetlands. It plays an important role by protecting the downstream elements from being overloaded with sediments and encourages settling of these particles.

Wetlands

The series of constructed wetlands is the second element in the treatment train and cleanses water discharged from the sedimentation basin, while the Yunnan Garden Wetlands (near Chinese Heritage Centre) cleanses water from Recreational Pond downstream. It utilises a shallow and extensively vegetated waterbody to remove f ine pollutants and nutrients from stormwater runoff by enhanced sedimentation, f ine filtration, and biological nutrient uptake processes. The presence of extensive lush greenery creates habitats and attracts an array of fauna.

Rain Gardens

Two rain gardens were constructed in this development to treat stormwater runoff from the pedestrian walkways through a prescribed filter media before discharging it into the Nanyang Lake and Recreational Pond.

Cleansing Biotopes

To provide further treatment to runoff, water from the wetlands and Nanyang Lake are recirculated into the cleansing biotopes to further improve the water quality before discharging the water to the existing canal along Pan Island Expressway (PIE). The cleansing biotopes are in the form of an artificially constructed wetland, consisting of nutrient-poor substrates that are planted with wetland plants known for their water cleansing capacity.

Waterfall and Yunnan Garden Wetland

The waterfall is a transitional feature of the treatment train. Segregating the Recreational Pond and the Yunnan Garden Wetland, the water from Recreational Pond would cascade over the waterfall during a storm event into the Yunnan Garden Wetland. Water is aerated at the cascade, increasing dissolved oxygen levels. This process helps in maintaining good water quality, prevents water stagnation and supports a balanced ecosystem. On dry days, water from the Yunnan Garden Wetland is drawn up to the water weir (at least 2-3 times a day for 1 hour) mechanically.

As part of PUB’s efforts to educate the younger generation about sustainable stormwater management, PUB has collaborated with Ministry of Education (MOE) to promote and build ABC Waters design features in school compounds for many years.

As the first President’s school, Yusof Ishak Secondary School (YISS) aims to retain its heritage and at the same time, be creative for a sustainable future. ABC Waters design features can link students to nature as well as the community and is also one of the features that contributes towards the sustainability initiative of the school.

In 2021, the newly relocated Yusof Ishak Secondary School has incorporated a bioretention basin (rain garden) in the school premises. Aside from their capabilities in stormwater detention and water quality improvement in the school compound, the rain garden enhances the visuals and biodiversity of the school, improving the learning environment for the students.

Rain Garden

The rain garden is located next to the Design & Technology studio and easily accessible from the nearby school field and fire engine access. The rain garden can treat runoff from about 11% of the total site.

The rain garden serves as an outdoor classroom where students can learn about water and nature in a real-life setting. It is designed as an experiential learning place and resource for the student population to deepen and extend their understanding in STEM (Science, Technology, Engineering, Mathematics) curriculum in the school. For example, Secondary One students were better able to appreciate and understand the filtration process and waterways in Singapore; Secondary Two students did a simple investigation of abiotic factors in ecosystems and biological sampling, this enabled more effective and in depth learning of ecosystems; STEM Club CCA students kept records of organisms thriving in the rain garden and this further fueled their curiosity and ignited passion in STEM. All these will help to inculcate a stronger sense of stewardship of Singapore’s precious water resource amongst our younger generation.

Extensive Greeneries

YISS showcases a myriad of green features in the school compound to alleviate overall ambient temperature and improve the aesthetic of the school. This includes roof top garden at 7th floor, E-deck at 2nd floor, garden at 3rd floor of Admin Block, and planter boxes at every floor. 21% native plant species are used in this project to promote biodiversity.

Rainwater Harvesting Tank and Drip Irrigation System

Rainwater harvesting is the practice of collecting and storing rainwater for reuse. Rainwater that is stored in the rainwater harvesting tank will be used in an irrigation system which controls the amount of water supplied to plants at regular intervals for landscape maintenance.

Developed and managed by the National Parks Board (NParks), the 90-hectare Jurong Lake Gardens is envisioned to be Singapore’s new national garden in the heartlands, a people’s garden for leisure and recreation, and a model for sustainability in green development. Jurong Lake Garden comprises of Lakeside Garden, Jurong Lake Gardens Central (including the Chinese and Japanese Gardens), Jurong Lake Gardens East, and Jurong Lake Gardens West that would be developed in phases. Jurong Lake Gardens West was completed in 2019 and was an ABC Waters Certified (Gold) project.

Within Jurong Lake Gardens West, a myriad of facilities is built to engage the communities to bring them closer to the park’s extensive water frontage. This includes a promenade plaza, water playground, boardwalks, multiple viewing decks and stream crossings. The major pathways into the key features of the park are designed barrier-free to allow visitors to fully enjoy the naturalised landscape built with vegetated and gravel swales and planted bioengineering features.

A cleansing biotope treats stormwater run-off and water from Jurong Lake. A water playground is integrated to utilise the treated stormwater after UV disinfection. Eco ponds receive treated water from the cleansing biotope as well.

The ABC Waters design features (swales and cleansing biotope) treat runoff from an equivalent 55.9 % of site area to comply with ABC stormwater treatment objectives. Educational signages are also placed at the ABC Waters design features around the park to bring awareness to the visitors about water sustainability, the concepts of ABC Waters and how these bioengineering techniques interplay with nature. Lush planting with 60 % of native species is used for the whole development, sustaining a rich variety of flora and fauna.

Vegetated and Gravel Swales

Conventional concrete drains were naturalised into both vegetated and gravel swales by lining with gravels or planting native sedges to enhance the aesthetics and visual appearance of Jurong Lake Gardens. Swales aid in collecting stormwater runoff and provide pre-treatment by removing coarse particles before flowing into the cleansing biotopes downstream. The presence of a lush landscape also attracts and nurtures a wide range of biodiversity in the park, such as birds, otters, and insects.

Intertidal Boardwalk

The 300 m long meandering barrier-free intertidal boardwalk provides the opportunity for visitors to get up close with nature along the shorelines. Many of the plant species along the boardwalk have evolved mechanisms to allow them to cope with constant inundation. Visitors will experience both the water and rich biodiversity as they travel along the boardwalk, crossing moderately dry grasslands, wet grasslands, and the lake itself.

Promenade Plaza

The promenade is designed for people to walk along the water’s edge. With existing banyan trees along the lake, sufficient shade is provided for visitors to stroll from lakeside entry all the way towards Chinese Garden. Lounge chairs and seating are positioned on the shore for visitors to enjoy the scenery over the lake.