4. ON FLOOD RISK MANAGEMENT 4.1 GENERAL Flood risk is defined as a combination of the probability of a flood event happening and the consequences (impact) if it were to occur and can be quantified in financial terms. When determining the effect of a measure, it can be assessed by comparing the investment costs with the reduction in risk. See also Figure 14. The challenge is to find the optimum. Paragraph 6.4 explains in short what is needed to come to such an optimum. At first the current flood risk is to be calculated. Then, with a set of measures determine the investment needed to stay at that level in the future, or set a protection level of 25, 50 and 100 years and assess what the costs are. The optimum is not only defined in financial terms, as other elements as reducing casualties, improving health and creating a liveable and prosperous city are all to be taken into account. 4.2 DESCRIPTION OF THE AREA The area on which the DRR team focused was the Sungai Pinang catchment and the historic city centre of George Town. These are two very different systems. The Sungai Pinang catchment originates in the Penang hills, and through several rivers, creeks and drains ends in the Sungai Pinang which discharges into the Malacca Strait. The catchment as well as the length of the rivers is small. Downstream, the system is in a highly urbanized area. Where the upstream catchment is in a hilly forest, there are also a number of retention ponds, drinking water reservoirs and bypasses. In the urban area of George Town, rainfall is collected in a drainage systems (mostly underground) and discharges through a number of outlets directly into the sea. The catchment and characteristics of the Sungai Pinang is shown in Figure 15. Figure 14: Risk versus investment Figure 15: Catchment and characteristics of Sungai Pinang • 37 • Figure 15: Some pictures of the area • 38 • JULY 10, 2018 DRR-TEAM MISSION REPORT - MALAYSIA - KUALA LUMPUR/PENANG • 39 • Figure 17: Flooding in the Sungai Pinang catchment 18a 18b Figure 18: Drainage system in the historic centre 18a Map with the location of the outlets 18b Example of one of the outlets • 40 • JULY 10, 2018 Figure 16 show some pictures taken by the DRR team. The picture on the lower right is in George Town, the other pictures are in the Sungai Pinang catchment. The picture of George Town is typical for the area: concrete, asphalt and no room to store water, only underground. The pictures from the river show that a significant part of the river is aligned, with concrete, to allow the water to discharge as soon as possible. It also shows that the city has turned its back to the river. Access to areas close to the river is blocked or very difficult. In the lower stretch of the Sungai Hitam (before it becomes the Sungai Pinang), suddenly a green area with trees and a natural river appears. DID in Penang has made an overview of areas frequently flooded by the Sungai Pinang, see Figure 17. The green dotted line is the boundary of the catchment of Sungai Pinang In the upstream part of the catchment, some retention ponds are built. For such a retention to be effective, strategic operation is needed: these ponds are most effective when used during the peak of an event. If they are used prior to or after an event, the impact is not optimal. During a field visit it was noticed that there is a fixed weir between the river and the pond. As a result, the operation of these ponds cannot be adjusted. Further upstream, two water supply reservoirs are constructed as well. Their operation is only focused on optimizing the water supply to the city. Also their capacity could be used during a flood event. As mentioned before, the area outside that boundary, in the historic city centre, drains directly into the sea, through a network of drains and outlets. During the meetings and discussions it became clear that many plans and projects exist, focussing on drainage, pumping stations, works and construction, barrages and collector drains and valves for the outlets. Most seem to focus on solutions on the spot, and not necessarily look for solution on catchment scale. DRR-TEAM MISSION REPORT - MALAYSIA - KUALA LUMPUR/PENANG • 41 • Figure 19: Example of bottlenecks • 42 • JULY 10, 2018 Bottlenecks During several site visits, it was noticed that in some locations construction of bridges and pipelines resulted in bottlenecks for the river. According to the representatives of DID, at these locations flooding occurs as well. The challenge here is that construction of the bridges is carried out by the city council, whereas river management is a task for DID. The pipelines are typically owned by a utility company such as the water supplier. 4.3 OVERALL FINDINGS ON FLOOD MANAGEMENT PRACTICE IN PENANG • Retention ponds are not managed optimally yet. There may be room to fine- tune their operations to mitigate the impact of flooding. • A similar observation is valid for the Water supply reservoirs upstream of Sungai Air Hitam and Sungai Air Terjun. As this is a different stakeholder, discussions are needed to find out whether the effective use of ponds is an option. • Bottlenecks in the system need to be removed. A number of bridges are too low or make the cross sections too narrow. As a result, they may act as a weir during higher water levels. DRR-TEAM MISSION REPORT - MALAYSIA - KUALA LUMPUR/PENANG • 43 • • 44 • JULY 10, 2018 5. TOWARDS AN ADAPTIVE DESIGN OF THE WATER SYSTEM 5.1 INTRODUCTION In order to get as many ideas (and involvement) from various stakeholders a charrette was organised. Method used: a charrette A charrette is a condensed design workshop in which, in this case, Dutch experience is combined with local knowledge, with the aim to achieve new shared discoveries and to learn from each other’s experiences. In this workshop drawing is used as connecting language between participants from different disciplines and with different backgrounds. In order to be effective a workshop like this should take 4 days. The Penang workshop lasted only 3 hours and was, obviously, very limited in time. Three hours is too short to develop a balanced vision but it helps to identify the main issues. More than 40 people attended the meeting in Penang Motive for this charrette Pulau Penang is frequently struck by floods, causing lots of damage. Without intervention this will even get worse in the future. Flash floods and storm events will occur more frequently and infrastructure and urbanization are changing rapidly The city of George Town uses a lot of cement and offers too little room for the water; there is hardly any space to store the water. Also the water cannot sink into the soil. Conditions are changing! This is true for the natural (climate) conditions as well as for the man made conditions. Main questions are: how can we deal with the increase of precipitation and how can we protect Pulau Penang better against flooding and reduce damage? To achieve this, three complementary strategies are needed (and being discussed in this report): 1. Improved forecasting resulting in a better early warning (chapter 3) 2. Effective disaster management (chapter 4) 3. Adaptive (re)design of the water system and the urban area The charrette was about this last strategy: • How can we realize a more robust and adaptive water system? • How can we develop the urban area in such a way that it becomes less sensitive to flooding? The ‘storyline’ used during the charrette is given in Annex E. DRR-TEAM MISSION REPORT - MALAYSIA - KUALA LUMPUR/PENANG • 45 • Figure 20: Charrette in Penang, 4th of June 2018 • 46 • JULY 10, 2018 5.2 OBSERVATIONS IN PULAU PENANG On Pulau Penang lots of projects are under construction or in preparation. The administration is eager to solve all problems as soon as possible. There are lots of individual projects but an integrated and holistic approach seems to be missing. In the present situation most solutions are: • found ‘on the spot’, • based on increased drainage capacity • realized as ‘concrete’ constructions. The rivers are an almost hidden quality in the urban fabric. They are hard to find, but when you have found them, you discover an overwhelming green area that really could add spatial, ecological and social value to the city, that could strengthen Penang’s identity. And along these rivers often still a lot of space is available. Space that can be used to increase storage capacity or to retain the water. As mentioned earlier, in the North East of Pulau Penang two systems are relevant: • the natural river-based system, the Sungai Pinang catchment area • the man-made system within the old colonial inner city of George Town These two systems are totally different, but they both require a system-based approach. In the natural based river system there are still many bottlenecks. Sometimes the river bed is too narrow and on other places the bridges are too low. During high water levels these low bridges hinder the run off and worsen the flooding. In the man-made system, the UNESCO heritage inner-city, there is hardly any space available. There you have to develop another kind of measures. 5.3 RESULTS OF THE CHARRETTE The participants shared the conclusion that solutions for the different assignments within a river system must be embedded in an integrated vision on the future development for that system as a whole. In what direction does Penang want to develop its river system, what should be its main characteristics and qualities? That integrated, holistic long-term perspective offers guidelines for the development of the individual projects in the mid- and short term.