Growing more sponge cities | The Star

THE term “sponge cities” is used to describe urban areas with abundant trees, lakes and parks designed to absorb rain and prevent flooding.

During the Selangor State Assembly sitting in November, Kota Kemuning assemblyman Preakas Sampunathan said the “sponge city” concept could address flooding.

He said the focus should be on prevention rather than corrective measures to deal with floods.

“We need surfaces that can absorb water and release it slowly.

“At the moment, we are big on building retention ponds but we need diverse ways to solve floods,” he said.

StarMetro spoke to experts to determine what sustainable methods could be used to mitigate flooding in the city.

Parks and open fields or green spaces can act like sponges to absorb rainwater.

Think City managing director Hamdan Abdul Majeed said nature-based solutions were increasingly being recognised as potential strategies for flood mitigation.

“Traditional flood defences like flood walls and being dependent on drainage systems (also known as grey infrastructure) may no longer be sufficient to address increasing climate threats.

“The nature-based solution is a climate-adaptation approach that leverages nature and functional ecosystems as integral infrastructure.

“It provides evidence-based solutions for both societal and environmental challenges.

Preakas: Focus should be on prevention, rather than corrective measures in dealing with floods.“The concept of sponge cities has been identified as a key example of nature-based solutions for urban areas.

“It is capable of minimising the impact of natural disasters, especially in urban settings with prominent water elements.

“Sponge cities have large expanses of natural areas, including green spaces and water bodies also known as blue spaces, which aim to absorb rain and prevent flooding,” said Hamdan.

He explained that the concept mimicked the natural hydrological cycle to help reduce the impact of flooding.

A sponge city essentially soaks in rainwater and retains excess stormwater, then filters and releases the water slowly, much like a sponge.

“It relies on a natural stormwater management infrastructure, with a focus on flood control and mitigating urban development’s impacts on hydrology and ecosystems.

Putrajaya has plenty of water bodies or blue spaces, which should help prevent flooding.

“This includes the use of permeable materials, construction of new retention ponds and restoration of wetlands, which would not only ease waterlogging, but also improve the urban environment.

“The availability of green and blue spaces serves as an asset that should be utilised in a high-density city.

“Through the sponge cities approach, we expect to significantly reduce damage to property and infrastructure, reduce economic losses and enhance community resilience.

“It is not only capable of dealing with a sudden excess of stormwater but also reuses it to help mitigate the impact of extreme heat,” he added.

Hamdan: Traditional flood defences may no longer be sufficient to address increasing climate threats.

Think City developed the Penang Nature-based Climate Adaptation Programme for the island (PNBCAP), touted as the first of its kind in Malaysia.

PNBCAP components include urban greening, stormwater management, fostering social and community resilience, and strengthening institutional capacity, Hamdan explained.

“The programme is a pilot initiative that will serve as a municipal framework for climate adaptation, with the potential for it to be adopted in other cities in Malaysia and elsewhere in the region,” he said.

Better way to manage water

According to Housing and Urban Futurist Resilient City consultant Mustapha Kamal Zulkarnain, Malaysia has an abundance of spaces that are not gazetted.

He said that after a 2005 flood, the Drainage and Irrigation Department (DID) came up with the Comprehensive Master Plan for Eco-Friendly Drainage or Pelan Induk Saliran Mesra Alam where the drainage system used the swale method (see sidebar).

Mustapha said such plans were typically designed for sustainable water management and urban development, factoring in environmental conservation and minimising negative impacts on ecosystems.

“Our drains are made of earth and they act like a sponge, whereby some rainwater is absorbed instead of being flushed away.

“Drains in newer housing developments such as Denai Alam, Shah Alam, are made using the swale method.

Mustapha: Maintenance of drains is critical to flood prevention, otherwise there will be back flow.“Playgrounds and fields are also great for water retention during a downpour,” he said.

The maintenance of drains are, however, critical in this system.

Without good maintenance, any drain, whether earth swale or concrete-lined ones will back flow, noted Mustapha, citing the confluence of Gombak and Klang rivers as regularly experiencing this problem.

Referring to the Denai Alam flooding in November 2022, he said it occurred once after 15 years and he attributed it to poor maintenance of drains.

“I was living there. I saw the drain water level rising but only to the brim. It didn’t flood roads or houses,” he said.

Mustapha said most local councils required developers to allocate 10% of their development for open space.

“Of that 10%, some 30% of it should be open space that can act as a retention pond.

“The developer may meet the open-space criteria with smaller scattered portions, which will be less impactful,” he noted.

He said that due to the scarcity of land, there was a need for SMART (surveillance, monitoring, analysis, rethinking, thoughtfulness) planning.

Mustapha said there was no need for new guidelines, but use innovative approaches instead.

“Use existing parks to dissipate the rainwater,” he said.

Kuala Lumpur Residents Action for Sustainable Development (KLRA+SD) chairman Tan Booi Charn said any plan to mitigate flooding would be welcomed.

“Under the Kuala Lumpur Structure Plan, experts also spoke about flood mitigation and making the drainage system more efficient,” said Tan.

She observed that floodwater was often muddy and that where the soil originated from should be investigated.

Underground water storage

The more concrete a city has, the less water can be absorbed by the ground.

Melasutra: Invest in mitigation projects to reduce impact on those living in flood-prone areas.As more green spaces are developed into grey areas (buildings and other concrete developments), people will face problems such as flooding, said Assoc Prof Dr Melasutra Md Dali from Universiti Malaya’s Built Environment Faculty.

“Since 2013, China and some Western countries have been working on solving issues related to climate change.

“We are not spared from climate change issues as we now have heavy rain in January and this affects places in Johor,” she pointed out.

“When the sea level is higher than rivers, there will be stagnant flooding,” she said.

Melasutra said that in China, water tanks were created underground to store excess rainwater from a downpour.

“Putrajaya has natural ponds and these will retain rain during a downpour.

“We need a holistic system that is comprehensive and interconnected – most developments only focus on using up the land.”

She said that for flood mitigation, underground water storage ideas would be the way forward and the stored water could be used during the dry season.

“We need to look at long-term investments with high returns.

“To mitigate traffic congestion, the LRT and MRT were built. They are expensive but impactful in the long run.

“Similarly we should invest in flood mitigation projects to reduce the impact on those living in flood-prone areas,” she added.