Thinking outside the box
“For Singapore, one of the major ways to prevent flooding is to try and reduce the ‘speed’ of the rainfall,” said Tan Ying Hao, senior manager at the Catchment & Waterways Department of the Public Utilities Board, under the Singaporean Government. “This means extending the time it takes for a raindrop to fall from the sky to the ground. The key words here are ‘interception’ and ‘infiltration’.”
Singapore is famous for its varied plant life, but especially rain trees, South American imports with giant canopies that retain water. “The trees have certainly done their part in catching rain in the middle of downpours, but that’s far from enough,” Tan said.
“For the past few years, the government has been championing the construction of rooftop gardens and water tanks, both on rooftops and below ground.
In addition, the city makes the most of natural drainage systems – rivers and streams that channel rainwater. “Before, we tended to build waterways with concrete banksandmadethemstraight in certain stretches,” he said.
“Now, we realize that the best way is to allow these natural drains to take their own courses, allowing the water to remain in transit for longer.”
Bioretention swales— long, depressions or trenches that receive rainwater runoff and are heavily vegetated to slow the movement of water — have been widely implemented as part of the board’s Beautiful, Clean Waters Programme, which aims to transform drains, canals and reservoirs into streams, rivers and lakes.
“It’s a design feature used widely across the island. We use small rocks instead of concrete for the bed and plant grasses and shrubs along the channels,” he said.
When he addressed SingaporeInternationalWaterWeek lastmonth,TharmanShanmugaratnam, Singapore’s deputy prime minister, urged global policy-makers to “think outside thebox” whentackling the threat posed by water.
Pedestrians walk past sandbags outside the Liat Towers shopping center in Singapore on July 22, 2010.