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This chapter reviews and compares Southeast Asia country practices on global, regional, and local practices for disaster risk assessment (DRA). DRA research and practices include and create a disaster risk management (DRM) solution. There are 11 countries in Southeast Asia, but only 10 countries are members of the Association of Southeast Asian Nations (ASEAN), except Timor-Leste. The key objective of ASEAN’s formation is cooperation in economic growth, social, regional peace and cultural development, disaster management cooperation, and humanitarian assistance at the regional level. The DRM system practiced in ASEAN member countries is discussed in this chapter. Furthermore, the system and findings of DRAs are also addressed. Globally, two DRA structures are discussed and compared, namely Index of Risk Management (INFORM) and World Risk Index (WRI). In addition, regional vulnerability assessment guidelines for regional and national levels are discussed. However, several selected studies and practices such as the Indonesian Risk Index (InaRISK) are being discussed at the local level. Overall, there is space for improvement of coordination in terms of data and technology sharing for DRM, especially for assessment. The finding of this review highlighted the complexity of DRA at the global and regional levels and encouraging community DRA among the ASEAN members.

Climate change is expected to alter the major components of hydrological regime such as streamflow and water availability. The magnitude and their impacts are still uncertain. Therefore, it is highly required to study streamflow and flood vulnerability in tropical river basins particularly urbanised basin such as Langat River Basin. This study aims to model the future streamflow of Langat River Basin due to climate change using Rainfall-Runoff Inundation (RRI) model. Daily rainfall data obtained from Department of Irrigation and Drainage Malaysia and topographic data from HydroSHEDS at 15-second resolution were used. The projected future rainfall (2075–2099) is extracted from MRI-AGCM3.2s under the worst carbon emission scenario, RCP8.5. The annual maximum series of 1-day rainfall is selected for statistical bias correction using Quantile Mapping. The General Circulation Model data were found to be greatly corrected with reasonable Nash–Sutcliffe efficiency, Percent bias and Root Mean Square Error values. The mean of maximum 1-day future rainfall in Langat River Basin is found to be inconsistent where parts of the upstream will experience an increment at about 7% while other parts decrease at 8%. Meanwhile, the rainfall at downstream area are expected to decrease at 40%. Based on RRI simulation, the future streamflow can achieve up to 92% increment.

The impact of climate change towards water surface resources is crucial, particularly in developing and non-developing countries. Groundwater as a main water resource is thus an essential. However, contamination due to hydrocarbon spills affects the groundwater as a water resource, especially as a main source of drinking water. This chapter investigates the light non-aqueous phase liquid (LNAPL) penetrations in double-porosity soil with different moisture contents and with or without vibration impact. It also explains the LNAPL penetration phenomena by employing image analysis. The physical laboratory experiments were implemented using an acrylic cylinder, a mirror, toluene and a Nikon D90 DSLR digital camera. Prepared soil was poured in an acrylic cylinder and compressed with compressor until it became 10 cm in height. LNAPL was then poured instantaneously onto the acrylic cylinder that was filled with soil sample. The LNAPL penetration patterns were recorded and monitored using a Nikon D90 DSLR digital camera. The processing technique was conducted at predetermined time intervals using Surfer software and Matlab routine to plot the LNAPL pattern. The results showed that a higher penetration rate of LNAPL occurred with higher moisture content and without vibration impact. The penetration time for LNAPL to reach the bottom of the soil sample was found to be longer for the soil that had low moisture content and with vibration impact.

The Best Management Practices for Sustainable Urban Drainage System including On-Site Detention have been introduced in the Storm Water Management Manual for Malaysia. Flash floods are becoming frequent in the urbanised areas in this country. Inefficient drainage system has been highlighted as one of the factors. Urban drains were reported incapable of coping with the unexpected heavy rainfall. Concrete drains are favourable in construction industry for economic reasons. An experimental research was conducted out to investigate the effectiveness of infiltration integration with drainage system to reduce flash flood. This laboratory research was conducted in the Universiti Teknologi Malaysia. Experiments were performed for selected drainage bed slopes and focussed on several spacing between precast drain sections along the system. The total and infiltrated flow rates, water surface and velocity profiles were examined. The results showed that drain flow rates were reduced by 60.9%–89.6% when the spacing between drain sections were enlarged. Meanwhile, the flow depths in drain sections were dropped by 48.2%–68.9%, and the water velocity was lowered up to 49% as the spacing between drain sections were increased. The study found that the drainage bed slope also influenced the performance of the infiltrated concrete drainage system.

The evolution in developed countries has taken a role in global warming and natural disasters such as flash flood, El-Nino, earthquake and groundwater contamination. The underground storage tank leakage problems and spillage of hydrocarbon liquid leading to the contamination of non-aqueous phase liquids (NAPLs) into the groundwater could reduce the quality of groundwater. This chapter is intended to investigate the behaviour and the pattern of NAPL migrations in double-porosity soil under vibration and intact conditions. The experimental model is developed by using kaolin soil type S300 and toluene as NAPLs. The kaolin soil was mixed with 25% of moisture content to produce kaolin granules in the soil column and vibrate under 0.98 Hz of frequency within 60 seconds. As a result, both specimen liquids completely migrated to the bottom of soil column: sample 1 has higher permeability compared to sample 2. This is due to the fracture in double-porosity soil under vibration effect and loosened the soil structure in sample 1 compared to good intact soil sample 2 with stronger and compact soil structure. In conclusion, this study proves that the dangerous hydrocarbon NAPL migration in fractured double-porosity soil has very harmful effect on the environment and groundwater resources.

This study explores the concept of hydraulic flushing gate with an automated control system as a flow control structure of the urban storm water system. The research team has implemented a flush gate with the automated control system to the flow of the water in a drainage channel. The flow control structure was used to determine the effectiveness of such design by applying the concept of virtually on a real-world drainage system at Jalan Astana, Kuching. Computer representations of the existing drainage system and flow control structure were built using EPA SWMM 5.0 model. The series of flow control structure was proven to hold the runoff from 10-year storm. The modelling result shows that there is 25.9% of flow reduction at outlet node. As a modification of the existing drainage system in the urban area involves high construction cost, by installing a flow control structure in the drainage system is an innovative way to control the flow of the water.

Time of concentration (T_c) is one of the main inputs in rainfall–runoff model which depends on catchment length, slope, soil properties and surface cover. Factor such as floodplain also has a significant contribution on the flood wave travel time. Floodplain which influences the flow and the travelling time is not possible to be calculated using common T_c formulae. One approach to handle this complex behaviour is to deploy the hydrodynamic model as part of the rainfall–runoff model. This chapter explains the application of hydrodynamic approach to determine T_c for large catchment with the effect of floodplain. A hydrodynamic river model for Sg Relai was developed as part of the rainfall–runoff model covering 460 km² catchment area. It includes channels covering 90 km long which is extended to the floodplain based on the digital terrain model. The simulation results show that once the flood water spill to the floodplain, the channel travelling time is delayed by several hours. The delay of the travel time increases as the rainfall intensity increase which demonstrates that hydrodynamic modelling with the integration of floodplain is capable to compute the variation of T_c.