Multiple methods to control floods

CALLS for better flood mitigation have been heard widely following the deluge that occurred in various cities and areas in the country over the past three months.

China’s “sponge city” concept has once again been highlighted as an alternative to our existing rain- water management systems, inclu- ding the Klang Valley’s SMART tunnel.

The reality of flood prevention is that it requires the integration of multiple methods. A clear lesson can be learned from the floods that occurred in several sponge cities in China last year.

The amount spent to transform Zhengzhou in China’s central Henan Province into a sponge city was about RM336mil, and yet it was submerged under a year’s volume of rain that fell in four days.

Predicting the intensity of rain still lacks accuracy, and rising sea levels caused by the climate crisis have been increasingly limiting the capacity of existing drainage infrastructure to channel rainwater away from flooded areas.

As risk analyst Nassim Nicholas Taleb remarked, “The rarer the event, the less tractable, and the less we know about how frequent its occurrence.”

Even the sponge city’s green features, such as parks and bioswales (channels designed to convey stormwater runoff while removing debris and pollution), have limitations in “soaking up” rainwater, as experienced by Zhengzhou, and need an elaborate drainage system to divert excess water.

Kuala Lumpur’s SMART tunnel has proven to be an innovative method that complements sponge city features.

On Dec 18 last year, it diverted five million cubic metres of rainwater after Kuala Lumpur was drenched by a month’s worth of rain in one day, preventing what could have been even more serious floods in the city.

Cities with a high flood risk should integrate the available methods, ranging from sponge city features, river dredging, extensive pump systems, retention ponds, seawall strengthening, coastal reclamation and polder systems (lowland reclaimed from the sea and used as a buffer) to SMART tunnel systems to increase resilience against flooding.

Adopting a single method won’t address the problem.

JOSHUA WOO

Penang