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This May marks the thirteenth anniversary of the opening of the SMART motorway tunnel system in Kuala Lumpur, which opened in 2007 and ushered in a new era of flood resilience in the Malaysian capital.
Malaysia has long been susceptible to flood risk, with the Malaysian government undertaking projects with international bodies to improve resilience to the hazard. In this blog, we look at the challenges faced by residents of Kuala Lumpur; how flood management and new flood data is helping the city become more resilient to flood; and what the future might hold under a changing climate.
Photograph above shows flooding in Kuala Lumpur, 12 May 2014.
A long history of flood risk in Malaysia
Between 1998 and 2018, there were 51 natural disaster events in Malaysia, affecting more than three million people; of these disasters, 38 were flood-related, meaning that flood caused more than 70% of the damage to the country (Malay Mail). Since 1991, 495 people have been killed as a result of flood, with over a million people displaced (Dartmouth). In financial terms, Malaysia experienced USD $2 billion of losses from natural disasters in the two decades up to 2018, with USD $1.4 billion of losses coming from flood (Malay Mail). The worst disaster in recent history was the flooding in Kelantan province, which caused damage worth USD $300 million (Floodlist 2015).
Malaysia is affected by flooding nearly every year during monsoon season, with Kuala Lumpur affected particularly by flash (surface water) flooding, which can cause a lot of damage in a short time. The Klang and Gombak rivers merge in the city (see Figure 1), where heavy development has narrowed certain sections of river (Floodlist 2014a). According to government research, this has resulted in a 300% increase in the water flow since the 1970s, from about 148 cubic metres per second before 1985 to 440 cubic meters per second in 2001 (Floodlist 2014a). Rapid population increase has placed further strain on the city’s infrastructure, resulting in flash floods such as those in October 2014, which turned car parks into lakes, and those of October 2017, where major roads were flooded in the Bangsar South area (Floodlist 2014b; Malaysiakini).
Figure 1: Klang Basin shown in grey, with Klang and Gombak rivers converging highlighted with white circle. JBA’s Kuala Lumpur flood map covers the city boundary shown in red.
Flood management projects
The Kuala Lumpur authorities have developed ambitious plans to make the city more resilient to flash flooding. The most striking of these is the Stormwater Management And Road Tunnel (SMART) project, which involved the construction of a unique multipurpose tunnel. The idea was born in 2001 as a solution to the problems caused by floods in the city centre which may have a short duration (often just three to six hours) but still have potential to cause damage. The tunnel would be used to divert and store stormwater, whilst allowing traffic flow when the tunnel was not being used for this purpose. (Floodlist 2014a).
The SMART system opened on 14 May 2007 and is the longest stormwater tunnel in south-east Asia, at 6 miles (9.7km) in length. The tunnel, in conjunction with the wider Kuala Lumpur Flood Mitigation System, has the capacity to store 300 million cubic metres of water. It cost upwards of USD $500 million to build, but was in use within three weeks of opening, and prevented seven potentially disastrous floods in the city centre in its first three years of operation (Floodlist 2014a). However, although the tunnel has made great headways into flood risk management in the city, additional measures have been required because not all floods can be managed by the system; for example, the 2017 floods in several parts of the city which a local MP stated were the result of a lack of investment in road repairs and the irrigation system at Kampung Pasir (Malaysiakini).
As a result, authorities have also created the River of Life programme, which the government says should prevent flash floods of this type (Malaysiakini). This regeneration and restoration project is based on a programme of cleaning the Klang river basin, coupled with planning and beautification work along the Klang and Gombak river corridor and an education programme for residents (Myrol).
A new flood map for Kuala Lumpur
As part of a study supported with funding from the Newton-Ungku Omar Fund (www.ancst.com/nuof) and Innovate UK for the project entitled 'Disaster Resilient Cities: Forecasting Local Level Climate Extremes and Physical Hazards for Kuala Lumpur' JBA has created 5 metre flood hazard maps for the city. These take into account engineered flood management in the city centre such as the SMART system. JBA’s newly-created flood maps complement the government projects by indicating areas with a fluvial (river) and pluvial (flash) flood hazard. Use of a high-quality terrain dataset and local hydrological data ensures that the maps provide a reliable way of assessing hazard for both flood types. The maps incorporate flood defences, including the SMART system, as well as providing an undefended view of flood hazard across the city.
For fluvial flood hazard two scenarios are mapped: an undefended scenario where no mitigation or defence systems are accounted for, and a defended scenario where the flood protection offered by SMART and other projects (such as work to increase channel capacity at the Tun Perak bridge and to create overflow channels as culverts on the Keroh and Batu rivers) is incorporated.
The underlying digital elevation data is a bare-earth Digital Terrain Model (DTM) provided by the Civil Engineering and Urban Transportation Department, KL City Hall and City Planning Department.
The maps have been created by calculating rainfall totals and river flow volumes associated with different return periods and allowing the flooding associated with each to spread across the surrounding terrain using JBA’s hydraulic modelling software (JFlow®) and Geographical Information Systems (GIS). Provision of rainfall totals was undertaken in collaboration with the Department of Space and Climate Physics at University College, London (UCL).
The maps demonstrate the positive effect flood management work has had on the city. For example, for the defended fluvial map, the channel capacity in downtown Kuala Lumpur, at the Tun Perak Bridge, is increased from the 5-year flow assumption to a 20-year assumption, to account for the engineering improvements to the Klang River channel in this location. 
Figure 2: Images from JBA’s 200-year return period 5m maps of Kuala Lumpur showing fluvial (blue) and pluvial (purple) flooding. Top: Undefended. Bottom: Defended, with SMART and other systems accounted for.
What next for Malaysia?
Climate science is showing that “It is likely that the frequency of heavy precipitation or the proportion of total rainfall from heavy rainfalls will increase in the 21st century over many areas of the globe” (Seneviratne et al 2012). Despite the threat this poses, the gap between total and insured losses is growing, and this means countries regularly affected by natural disasters such as flood could see their ability to recover from more regular and more severe events diminished (Swiss Re 2020) . In Malaysia, industrialisation also plays a large part in the challenges faced by the country, with recorded natural disasters becoming a more regular occurrence since Malaysia’s rapid period of industrial growth in the 1990s (see Figure 2) (Malay Mail).
Figure 3: Natural disaster events in Malaysia by year 1963-2018 (Source: EM-DAT CRED).
It’s clear that effective flood risk management and mitigation is essential to build resilience to the hazard, especially in a changing world which could see more frequent and intense floods in future. Access to the latest knowledge in climate science and hydrological research is one of the key factors in informing flood risk management strategy. If you’re interested in finding out more about how JBA’s work in flood risk science can help you, please get in touch using the form.
References
Dartmouth Flood Observatory. 2020. Global Archive of Large Flood Events. [online] Available at: http://floodobservatory.colorado.edu/Archives/index.html Accessed 24 April 2020.
EM-DAT CRED (The International Disaster Database: Centre for Research on the Epidemiology of Disasters). 2020. [online] Available at: https://emdat.be/ Accessed 6 May 2020.
Floodlist. 2014a. SMART Tunnel, Kuala Lumpur, Malaysia. [online] Available at: http://floodlist.com/asia/smart-tunnel-kuala-lumpur-malaysia Accessed 24 April 2020.
Floodlist. 2014b. Kuala Lumpur Flash Floods Turn Parking Lot Into Lake. [online] Available at: http://floodlist.com/asia/kuala-lumpur-floods-turn-parking-lot-lake Accessed 24 April 2020.
Floodlist. 2015. Malaysia Floods – Kelantan Flooding Worst Recorded as Costs Rise to RM1 Billion. [online] Available at: http://floodlist.com/asia/malaysia-floods-kelantan-worst-recorded-costs Accessed 24 April 2020.
Malay Mail. 2018. Climate-related natural disasters cost Malaysia RM8b in last 20 years. [online] Available at: https://www.malaymail.com/news/malaysia/2018/10/12/climate-related-natural-disasters-cost-malaysia-rm8b-in-last-20-years/1681977 Accessed 24 April 2020.
Malaysiakini. 2017. KL hit by flash floods following afternoon downpour. [online] Available at: https://www.malaysiakini.com/news/400084 Accessed 24 April 2020.
Myrol (Malaysia River of Life). 2020. River of Life (ROL) Public Outreach Programme. [online] Available at: http://www.myrol.my/index.cfm Accessed 24 April 2020.
Newton-Ungku Omar Fund. 2020. Disaster Resilient Cities – Forecasting Local Level Climate Extremes and Physical Hazards for Kuala Lumpur. [online] Available at: https://www.ancst.org/nuof/ Accessed 6 May 2020.
Seneviratne, S.I., Nicholls, N., Easterling, D., Goodess, C.M., Kanae, S., et al. 2012. Changes in climate extremes and their impacts on the natural physical environment. In: Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation [Field, C.B., Barros, V., Stocker, T.F., Qin, D., Dokken, D.J., et al (eds.)]. A Special Report of Working Groups I and II of the Intergovernmental Panel on Climate Change (IPCC). Cambridge, UK, and New York, NY, USA: Cambridge University Press, pp. 109-230.
Swiss Re. 2020. Natural catastrophes: Closing the protection gap together. [online] Available at: https://www.swissre.com/risk-knowledge/mitigating-climate-risk/natcat-2019.html Accessed 24 April 2020.
