Feature pic Drainage Kuching (Arieff Zafir)

Fighting Floods with Better Drainage in Kuching

Outdated drainage in Kuching is intensifying flash floods and leaving communities vulnerable. Infrastructure must improve, plans streamlined and solutions account for state-specific conditions.

WHEN A deluge of rain hit Kuching, Sarawak in late August, it brought back the nightmare of the flood in 2021 that left Jeremy Aaron and his family stranded for 3 days.

“The first day was very kelam-kabut (hectic),” says the resident of Kampung Tabuan Dayak. “Everyone rushed to salvage their electric items…We stayed on the second floor the whole time, and called our elderly neighbours to check on them.”

(Feature image: Drains in Kuching are woefully inadequate to cope with denser cities and extreme rainfall  |  Photo by Arieff Zafir)

In Malaysia, as globally, floods are the most common environmental disaster. Flooding is expected to only increase with sea level rise and extreme weather events coupled with poor drainage systems and rapid urbanisation.

Sarawak experiences an annual average rainfall of 3,830 mm, which is around 1,000 mm heavier than the rest of Malaysia. In fact, inland Sarawak has the highest annual rainfall in the whole of Malaysia; Long Akah, near Baram river, experiences more than 5,000 mm.

Average rainfall has not changed but during the monsoon, some months are seeing heavier rainfall. These extremes have caused greater river flow variability, which increases the risks of flooding. In coastal areas, this is worsened when heavy, continuous rainfalls coincide with king tides.

By 2050, low-lying areas along the Sarawak River, including parts of Kuching City, are expected to face floods of 1 – 4 m deep due to climate change, rising sea levels and increased rainfall.

  • 1—2 m high floods: Jalan Astana, Jalan Green, Jalan Satok, Jalan Stapok, Jalan Tun Datuk Patinggi Haji Abdul Rahman Yakub, Sungai Maong, Matang Jaya, Sarawak Museum
  • 2—3 m high floods: Kuching Isthmus and the Bintawa area
  • 3m high floods: Kuching Esplanade and 1.5km inland, Sungai Maong, Richmond Hill, Batu Kawa

Scenarios assuming a 10cm rise in sea-level and extreme heavy rainfall by 2050:  Source: Kuok, KK, et al. (2022) Climate change impacts on sea level rise to flood depth and extent of Sarawak River. Frontiers in Water.

Kuching consistently suffered high flood losses economically in Sarawak compared to other divisions in the state, with RM281,677 in 2022 and RM107,150 in 2023.

One of the worst-hit areas for floods is Kampung Tabuan Dayak. It is named after Tabuan River, a tributary to Sarawak River.

The same scene replays each time.

Same old flood story

First the river swells, spilling into the drains. Then the floodwaters invade residents’ homes and destroy their furniture and floorboards. For hours after, they watch helplessly as the floodwaters refuse to recede.

Eventually, the fire and rescue department and civil defence force arrive to clear sludge from clogged drains and provide boats to evacuate victims to temporary flood relief centres.

Youth volunteers and, occasionally, local politicians distribute emergency food. Then comes the heavy lifting of cleaning out their homes and discarding belongings damaged by the flood.

A week after being flooded, Jeremy Aaron’s home in Kampung Tabuan Dayak is still a wreck. Jeremy is pictured top left with his parents Gary anak Rentap and Neos Egoh. (Arieff Zafir)

Since 2010, flash floods have happened so frequently that about 30% of the original residents have abandoned the village, says Jeremy, who grew up there. On one of the village’s worst-affected streets, Lorong 10A, only 2 – 3 families have remained.

It is tough when floods frequently disrupt daily life and livelihoods, damage property, and pose serious safety and health risks.

Cars are a particular concern. It costs residents RM2,000 – 7,000 to repair their cars each time they are damaged by floods. Some are beyond repair. As a result, residents park their cars on higher ground whenever it rains.

“You’ll see tonight, everyone will park their cars further outside (where it’s higher ground). It’s as though a function is happening,” says Jeremy wryly.

Wildlife risks

He adds that animals such as scorpions, snakes and even crocodiles emerge after the floods. “It happens such that now you can even see crocodiles in the drains some evenings.”

His mother, Neos Egoh also laments that the floods have disrupted their farming activities. “People used to farm, garden and plant corn and vegetables. Now, no more.”

She blames it on surrounding construction, such as the building of a nearby megamall. It is located just along the Tabuan River, which she says has also been narrowed and overflows each time it rains.

As a result, “every time it rains, when it’s high tide, mesti kena (we will get hit by floods). Confirm!”

And while they have “always had heavy rain,” she says, “now, even after just 30 minutes, the water rises so fast, and there’s nowhere for it to go.”

Areas prone to floods such as Batu Lintang carry flood warnings (Arieff Zafir)
Areas prone to floods such as Batu Lintang carry flood warnings (Arieff Zafir)

As water flows off impermeable surfaces like concrete and asphalt, it overwhelms drainage systems not designed to handle such volume, says professor of environmental management Dr Haryati Shafii.

But the causes of such flooding are complex. “It is a combination of factors, mainly the physical environment (climate) where we experience heavy rain, as well as the city area lacking flora cover to absorb the water through the soil.

“In addition, in city centres like the Kuching city area, some of the drainage systems can be old. With poor management and maintenance, along with overpopulation and high speed of development, it can cause water to overflow.”

Creaking infrastructure

Haryati has studied how weakening drainage infrastructures can lead to flash floods in areas surrounding Kuching.

“Are the drains—built 10 – 15 years ago—suited for the climate conditions of the present?”

The result is waterlogged streets, submerged homes and a community left alone to cope with the damage.

Chong Chieng Jen, MP for Stampin, has been vocal about the issue.

“The flash flood problem in both Stampin and Kuching [city] areas, by the looks of it, is getting worse in recent years…If there’s some heavy rainfall for about half an hour, you get lots of patches of areas affected by flash floods,” he says.

Concrete jungle

“Floods are made worse by the fact that a lot of natural grasslands—that are supposed to be water retention areas—are, because of rapid development, turned into commercial residential areas,” Chong explains.

“These projects are not just changing the landscape; they’re disrupting natural water flow and clogging up existing drainage systems.”

While the state’s DID has conducted drainage master plan studies in Kuching, Chong argues that they need to be more comprehensive, particularly for new development projects.

Without that, “it’s almost impossible to manage the drainage system for the entire city,” he says.

Shortening the leash

He emphasises the need to consider how rainfall will be discharged and the potential for flooding in surrounding areas, urging stricter conditions on developers to build adequate drainage systems.

He called for greater accountability from the DID and the Minister of Public Health, Local Government, and Housing. The departments did not respond to requests for an interview.

M: Macaranga: Drainage - Media - Liani MK - Editing Draft - 2 - Common Flood Solutions - Liani MK
Poster - Common Flood Solutions - Mobile (Liani MK:Macaranga)

The governments’ response to flooding nationwide has been a mix of emergency interventions and longer-term projects. Nationally, last year’s Budget 2024 earmarked RM50 million to repair flood retention ponds, and RM20 million for local authorities to carry out drain repairs and upgrades.

In this year’s Budget 2025, RM150 million is allocated to local authorities and the DID. Meanwhile, RM300 million will go to the National Disaster Management Agency (NADMA) for flood preparedness. Additionally, 8  flood mitigation projects have been completed, while 12 more are progressing.

But are these infrastructure funds solving problems?

In 2016, RM150 million was approved under the 11th Malaysia Plan for the Sarawak state to implement the Sungai Sarawak Integrated River Basin Development Project (PLSB). It was designated to tackle the persistent floods in Kuching and Kota Samarahan.

Dredging the Tabuan River was in that package.

Poster - PLSB Sungai Sarawak Mobile (Liani MK:Macaranga)

However, following the 14th General Election in 2018, the project came under review by the newly-elected Pakatan Harapan (PH) government, says Batu Lintang assemblyman See Chee How. Kampung Tabuan Dayak is in the Batu Lintang constituency.

The project was eventually re-approved in 2020. But tenders for the project were only called in late 2023. After delays spanning almost 8 years, the project is set to move forward again.

The federal Energy Transition and Water Transformation Ministry (PETRA), has approved RM191 million for its implementation, contractors have been appointed, and the target completion date is two years.

Paying the price

“This is a ‘good’ example of how Sarawak and Sabah have been neglected over the years,” says See. He is unhappy at how political upheavals and changes in Peninsular Malaysia disrupt projects in Sarawak and Sabah that require immediate attention.

And now, See is worried that the PLSB might be outdated.

“One side of an area [in Batu Lintang] for example—which was earlier reserved for drainage widening purposes—has now been taken by a vocational school extension. Some of the facilities are there, which can of course be moved.

“But who’s going to bear the cost of everything? It’s all these small things that can cause delays and become problems,” he says.

Other delays may occur when areas earmarked in the PLSB for water retention ponds are actually situated on heritage sites. One is the old Nurses’ Quarters, whose potential destruction is currently the subject of protests by local heritage groups.

At least it’s moving

Still, Dr Sheikh Kamran Abid, a flood management researcher, commends the government’s for moving forward with the PLSB.

Kamran emphasises that well-designed drainage systems can significantly reduce flood risks and prevent water-induced structural damage.

But he is worried that “without a comprehensive strategy to maintain the drainage system, overhaul the drainage infrastructure and integrate sustainable urban planning practices, we’re just delaying the inevitable,” referring to flood-related damage and losses.

Just after 10 minutes of rain, the drain along Lorong Carmelite in Batu Lintang quickly fills; under PLSB’s Package 2, it will be deepened to 2.6 m  and widened to 3.5—4 m; consultants, the DID and politicians discuss its execution (Arieff Zafir)

Add into the mix climate change.

Many of the existing drains were designed to manage the rainfall patterns and urban conditions of the past, says hydrology and urban drainage management researcher Dr Charles Bong Hin Joo of Universiti Malaysia Sarawak (UNIMAS).

“Previously, the Intensity-Duration-Frequency (IDF) curve and Rainfall Temporal Pattern (RTP) were based on past rainfall trends. However, with climate change shifting these patterns, using historical data alone is no longer effective,” Bong explains.

Including climate change

To account for future rainfall patterns, the DID released an updated Hydrological Procedure 26 (HP26) in 2018. This procedure introduces the Climate Change Factor (CCF), developed by NAHRIM in 2013.

“Incorporating this factor ensures that urban drainage systems are designed with an understanding of future rainfall trends, not just past ones,” Bong says.

This proactive measure helps address the increased intensity and frequency of rainfall events predicted in Kuching’s future.

In addition, the Sarawak Urban Stormwater Management Guideline (SUStoM), now in its third edition, emphasises sustainable stormwater management by promoting the “control-at-source” approach, such as a subsurface detention system.

Managing stormwater

What this does is it temporarily stores stormwater during peak events and gradually releases it later, to prevent overwhelming the drainage system. Bong lauds this as a paradigm shift from the reactive, rapid stormwater disposal—which seeks to immediately dispose of floodwaters.

“For any new development or redevelopment in Sarawak, the post-development peak flow must not exceed the pre-development flow, ensuring that future developments do not exacerbate flooding risks,” Bong says.

Drainage design must take into account future risks of climate crisis impacts. (Arieff Zafir)
Drainage design must take into account future risks of climate crisis impacts. (Arieff Zafir)

With these new design guidelines, planners and engineers are better equipped to build resilient drainage systems that can withstand the evolving hydrological challenges posed by climate change.

Ultimately, Bong hopes for a single platform hosting “information of all existing drainage systems from all the stakeholders”.

“As of now, there are quite a number of stakeholders involved in the management of drainage systems,” he points out.

“For example, the DID is the custodian of the information regarding the main drainage system and the discharge to the river; while the local councils are the custodians of the information for smaller internal drainage in the city where the maintenance [is] done by them.”

All in one place

“A single platform … will [make it easier for] design engineers to obtain vital information for the design of new drainage systems.”

Flood management researcher Kamran supports this, adding that the public should also be able to access the data. In addition, he advocates integrating remote sensing and geographic information system (GIS) software to easily map flood-prone areas.

“In a flood crisis situation, success depends on getting timely, accurate, precise statistics, and readable information,” says Kamran, who conducts research on integrating GIS in flood mitigation in Malaysia.

“If you have exact information about, say, your neighbour experiencing a flood, you might try and save them. We need information to locate whenever a disaster happens—whether it is before or after.”

There are many systems that can better manage drainage, including automated flushing gates, which can be used on existing infrastructure, says academic Charles Bong (Arieff Zafir)
There are many systems that can better manage drainage, including automated flushing gates, which can be used on existing infrastructure, says academic Charles Bong (Arieff Zafir)

“Projects involving drainage improvements normally involve high cost,” says Bong.

But there are cheaper, innovative approaches to improve flood management.

For one, he has run a pilot study using subsurface stormwater modules installed under parks. These underground storage units can detain excess water, promote water infiltration into the soil, and prevent sudden surges in runoff that can overwhelm the existing drainage network.

In his pilot, the system detained up to 95.6% of intense rainfall, thereby reducing the volume of water flowing into drainage systems. Bong reckons this is a feasible solution for Kuching given the city’s abundant green spaces.

Optimising the drainage system

Another cost-effective solution is to manage flow during heavy rainfall. This involves using flow-control gates and integrating real-time monitoring via an Intelligent Stormwater Management System (I-StoMS). These could optimise the capacity of different sections of the drainage system.

Preliminary studies using this approach in Kuching have already shown a 25.9% reduction in downstream flow during flash floods.

But for the rest of the state, Bong warns against a one-size-fits-all approach.

Sibu, for example, is built largely on peat, which leads to waterlogging and misalignment of drains. And in Bintulu, its proximity to the sea causes backflow issues during high tides. These examples illustrate that region-specific solutions are needed to address the different challenges across Sarawak.

Funds are limited and need to be spent carefully: this drain is supposed to be widened under the PLSB but this vocational school extension has been built in the reserve land (Arieff Zafir)
Funds are limited and need to be spent carefully: this drain is supposed to be widened under the PLSB but this vocational school extension has been built in the reserve land (Arieff Zafir)

Stakeholders laud the government’s recent investments in drainage infrastructure, guidelines and research.

But these funds are only a short-term fix, says researcher Kamran. “You have to understand that any amount is never enough whenever a flood happens…The key issue is they have to utilise and allocate the funds properly. So whenever we start a project, there needs to be proper implementation.”

Kamran also stresses the need for collective action, rather than playing the blame game. “Flood is not only ‘my problem’ or ‘your problem’…It is a community problem. When a disaster happens, we have to deal with it collaboratively.”

Still alone

For the time being though, the residents of Kampung Tabuan Dayak are the ones who must continue to bear the brunt of the floods. “The government talks about infrastructure spending, but we hope to see the results,” says Neos Egoh.

“When it rains heavily, tidak sedap tidur (you can’t really sleep),” says her son Jeremy. “You check every minute just to see if your house is flooded.”

[Edited by SL Wong]

Earth Journalism Network logo

This story was supported by Internews Earth Journalism Network.

Liani spent 3 months working on this story. She did online research on floods and drainage on research and government agency websites like that of the Department of Irrigation and Drainage, and consulted politicians and drainage researchers.

During her one-week fieldwork in August, she met and followed an assemblyman to various sites within his constituency in Kuching to observe the progress and challenges of a recent federally-funded drainage project. She also viewed models of potential drainage solutions and visited local flood victims.

In addition, Liani produced her own infographics and map.

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