Experts: Floodwater facility may not be ideal for KL

Kuala Lumpur City Hall’s (DBKL) feasibility study on building an underground storage system to mitigate flooding should be nearing its completion date.

The idea for the system was first mooted by former Federal Territories minister Datuk Seri Shahidan Kassim in June last year.

Shahidan had said DBKL would work with Drainage and Irrigation Department (DID) to build a high capacity groundwater storage facility to prevent flash floods in Kuala Lumpur.

This project is separate from mayor Datuk Seri Mahadi Che Ngah’s request last month for RM500mil from the Federal Government for infrastructure projects such as building water retention ponds and flood walls to prepare for future floods.

The Statistics Department revealed last month that in Kuala Lumpur alone, the December 2021 floods caused an estimated damage of RM32.4bil.

In a recent interview with Mahadi on the progress of the consultants hired for the study, he said at least six months was needed to study the viability of the project and come up with findings.

“Our consultants are studying the specifications of the groundwater storage tunnel and they need to collect data from the lowest point to channel water via gravity.

“It is cheaper to rely on gravity rather than build pumps.

“And then there is slope analysis, terrains and the topography as well as calculating rainwater intensity in all areas,” he explained.

Mahadi added that this project would cost a lot of money and because it would be borne by taxpayers, it was crucial that all the data was collected before going forward with the project.

Underground storage

The study will determine the viability of building underground chambers to hold floodwaters during a flood before releasing it into the river during low tide.

Kuala Lumpur currently has a similar system in place which is the Stormwater Management and Road Tunnel (SMART Tunnel).

A 9.7km bypass tunnel, its function is to divert excess floodwater at the confluence of Sungai Klang and Sungai Ampang into the SMART Tunnel system.

Since it was opened in May 2007, the tunnel has diverted floodwaters 40 times and averted about RM1.4bil in public damage.

The SMART tunnel only covers flooding around locations such as Masjid Jamek, Jalan Tun Perak, Leboh Ampang, Jalan Melaka and nearby areas, sending water into the Taman Desa catchment area.

However, flash floods also occur around Jalan Tun Razak, Kampung Baru, Jalan Gurney, Jalan Semarak and Kampung Kasipillay, which involve other rivers.

And because of the excessive rainfall brought on by extreme weather conditions and global warming, experts predict that things are only going to get worse.

As such, drastic long-term measures are required, but is building a multibillion ringgit underground tunnel the solution?

Tokyo’s plan in KL

“In Tokyo, due to space constraints, the city had to go underground and it works because that’s the Japanese way.

“They are disciplined and it fits with their culture.

“Do we have that culture?” asked former DID engineer Balachandran Naicker, 68.

Balachandran reminded that Kuala Lumpur’s flood mitigation plans carried out in the 1970s and 1980s did very little to solve the problem.

Following big floods in 1971, DID targeted three key areas to alleviate floods in the city, and the first one was restructuring the three main rivers of Sungai Batu, Sungai Gombak and Sungai Klang, as well as deepening and widening the tributaries.

Other strategies included creating flood retention ponds to prevent low-lying areas from flooding as well as the construction of three main dams at each river.

“When the SMART Tunnel was mooted and built in the early 2000s, it was probably the most significant move carried out to solve the perennial problem that has been plaguing the city for decades.

“While it did the job of moving water from open surface drains into downstream well enough, it did not, however, solve flooding in areas outside its reach,” he said.

So while some may believe that building another tunnel is a possible solution, are we looking at the right model?

In multiple media reports, Shahidan mentions Tokyo’s underground tunnelling system as an example, after visiting the city with Mahadi last year.

But is Tokyo’s system the right fit for Kuala Lumpur?

Balachandran does not think so.

“Tokyo’s climate and geography is challenging, with a monsoon season that brings with it torrential rain and typhoons, and the city is also prone to earthquakes.

“About 100sq km of the city is below sea level and rapid urbanisation has only made the city sink further.

“Moreover, most of the consumable space is hard, so when the rains pour there are surface run-offs and little room to build discharge channels and water overspills,” he added.

Balachandran feels that perhaps a more suitable system for Kuala Lumpur is the one in Hong Kong.

Sponge city concept

“In Hong Kong, underground space has been used for flood mitigation whereby the city can function like a sponge and the stormwater can be absorbed, stored and cleaned on rainy days, and later, released and reused when needed,” he said.

Basically, a sponge city is an urban space that has been designed to cope with excess rainfall using different techniques.

Instead of having to deal with flash floods and surface run-off from rivers bursting its banks and overflowing drains, sponge city design can mitigate or prevent it from happening by naturally absorbing the water.

Its measures include having rooftop green spaces, storage to harvest rainwater, creating more lakes and ponds to hold excess water, planting more trees and building roads with porous surface materials.

Balachandran also feels that the current SMART tunnel system can be extended to include other areas.

SMART’s first chief operating officer Mohd Fuad Kamal Ariffin said MMC-Gamuda, which constructed the SMART tunnel and the MRT, had the expertise and experience to do it.

“The technology of their tunnel boring machines has improved and can easily handle Kuala Lumpur’s highly-weathered limestone,” he said.

Keep retention ponds

Additionally, Balachandran and Mohd Fuad reiterated the need for the government to gazette flood retention ponds in Kuala Lumpur.

“If flood retention ponds are alienated for development, it will affect the storage capacity (of the pond) and this will affect the surrounding area as well as SMART Tunnel operations.

“Building tunnels costs a lot of money, hence it is always better to maintain our retention ponds,” Mohd Fuad said.

“Retention ponds should never be touched for development and regular maintenance of the pond is also crucial,’’ added Balachandran.

“The pond’s reserved buffer zones should only be touched for maintenance work,” he stressed.

Based on the 2019 Auditor General’s Report, Kuala Lumpur MPs highlighted that six retention ponds used for flood mitigation had been approved and alienated for development.

The six ponds were Kolam Batu, Kolam Nanyang, Kolam Delima, Kolam Taman Wahyu, Kolam Batu 4 ½ and Kolam Taman Desa.

However, this was later clarified in Parliament by the then deputy Federal Territories Minister Datuk Seri Jalaluddin Alias, who said only two flood retention ponds had been alienated for development.

Jalaluddin said only the ponds in Taman Wahyu and Delima in Kepong had been approved on Jan 18, 2018.

No approval was given for the other four ponds.

Nanyang pond is included in the Sungai Jinjang Flood Mitigation Plan.

However, it should be noted that parts of the Taman Desa flood retention pond were alienated for development despite it being a threat to the SMART Tunnel’s operations.

But part of the government’s conditions was that the company must guarantee that the development would not reduce the capacity of the pond.

As the developer was unable to do so, the deal was eventually cancelled by the government.

A similar situation also happened with Kolam Batu in Jalan Kelang Lama, whereby a development order was cancelled because the company was not able to fulfil several conditions.

Sources within DID told StarMetro then that the alienation of Taman Desa pond posed a threat to SMART Tunnel operations.

“Although the project was cancelled, there is no guarantee that in the future, someone else may want to develop it,” said a source.

“DID can only advise the government.

“The decision to take into consideration our comments depends entirely on those with power,” he said, adding that it was better to gazette the ponds to guarantee that it was protected in perpetuity.

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