A tropical island surrounded by seas, Singapore receives abundant rainfall especially during the monsoon seasons. Historical data show that over the last three decades, Singapore has experienced more intense rainfall events, and these are becoming more frequent. The growth of urban areas has also led to greater stormwater peak flows from developed areas into canals. There are also pockets of low-lying areas which are prone to flooding, especially when intense storms coincide with high tides.
Recognising the impact of greater weather uncertainties and urbanisation on drainage management, PUB has revamped its stormwater management approach to introduce greater flexibility and adaptability to our drainage systems.
This “source-pathway-receptor” approach looks at catchment-wide solutions to achieve higher flood protection. This holistic approach covers the entire drainage system, addressing not just the drains and canals through which the rainwater travels (i.e. “Pathways”), but also where rainwater falls onto the ground (i.e. “Sources”) and the areas where floods may occur (i.e. “Receptors”).
PUB included a new requirement, which took effect on 1 January 2014, for developers to implement “source solutions” to slow down surface runoff entering the public drainage system. These on-site measures could include detention tanks and/or ABC Waters design features which will help introduce more flexibility within the existing drainage system.
To strengthen “pathway” solutions, PUB raised the design standards in 2011 for drains to cater for more intense rainfall events. Depending on the size of the catchment, this could mean an increase of between 15% and 50% in drainage capacity.
In 2011, PUB also raised the requirements for the minimum land reclamation levels, as well as platform and crest levels for new developments and redevelopment sites, under its revised Code of Practice on Surface Water Drainage. These “Receptor” measures provide additional flood protection for buildings and key infrastructure.
The “Managing Stormwater for Our Future” publication presents an overview of PUB’s stormwater management strategies, approach and requirements that will help prepare Singapore for the future. It also outlines plans for 12 waterways in Singapore.