Effectiveness of Runoff Control Legislation and Active, Beautiful, Clean (ABC) Waters Design Features in Singapore

Xue Goh,Chris Zevenbergen,Mohanasundar Radhakrishnan,Assela Pathirana

doi:10.3390/w9080627

Xue Goh, Chris Zevenbergen + Show 2 more

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https://doi.org/10.3390/w9080627

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Abstract

Storm water management in Singapore has always been a challenge due to intense rainfall in a flat, low-lying and urbanised catchment. PUB’s (Singapore’s National Water Agency) recent runoff control regulation limits the runoff coefficient to 0.55 for developments larger than or equal to 0.2 ha. The use of Active, Beautiful, Clean (ABC) Waters design features are encouraged to attain peak runoff reduction. Hence the paper focuses on (i) determining the actual hydrological response regime of Singapore using the relationship between runoff coefficient (C), land use and slope; and (ii) investigating the effectiveness of ABC Waters design features in delaying and reducing peak runoff using a modelling approach. Based on a Storm Water Management Model (SWMM) model and using elevation, land use and soil data as inputs, the peak C-values were obtained for 50 m × 50 m grid cells. The results show that for the same land use, the one with steeper slope resulted in a higher runoff coefficient. Simulations were carried out in two study areas, Green Walk District and Tengah Subcatchment, where ABC Waters design features (such as porous pavements, green roofs, rain gardens) and detention tanks were incorporated to reduce C-values. Results showed that peak C-values can be reduced to less than 0.55 after increasing the green areas and constructing detention facilities. Reduction in peak discharge (22% to 63%) and a delay in peak discharge by up to 30 min were also observed. Hence, it is recommended to consider the relationship between slope and land use while determining runoff coefficients; and to incorporate ABC Waters design features in urban design to reduce the peak flow and runoff coefficient (C).

Highlights

Urbanisation results in hydrological changes such as increased overland runoff due to increased imperviousness [1]
It is recommended to consider the relationship between slope and land use while determining runoff coefficients; and to incorporate ABC Waters design features in urban design to reduce the peak flow and runoff coefficient (C)
This paper focused on establishing the actual hydrological response regime of Singapore and the relationship between runoff coefficient, slope and land use

Summary

Introduction

Urbanisation results in hydrological changes such as increased overland runoff due to increased imperviousness [1]. The increase in runoff exacerbates the flood risk, which is expected to increase further due to climatic, land use and further changes [2]. Cities across the world are adapting to urban flooding using various adaptation measures comprising innovative drainage design approaches, policy measures, legislative controls, and so forth [4,5,6]. The risk of flooding is likely to affect the liveability and sustainability in densely populated cities like Singapore, which is highly urbanised but with a small land area of 718 km2 [7]. Storm water management in Singapore is a challenge due to its geographical location, climatic regime and topography.

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