Flood damage and risk assessment for urban area in Malaysia

Abstract

In recent years, flood risk map has been widely accepted as a tool for flood mitigation. The risk of flooding is normally illustrated in terms of its hazard (flood inundation maps), while vulnerability emphasizes the consequences of flooding. In developing countries, published studies on flood vulnerability assessment are limited, especially on flood damage. This paper attempts to establish a flood damage and risk assessment framework for Segamat town in Johor, Malaysia. A combination of flood hazard (flood characteristics), exposure (value of exposed elements), and vulnerability (flood damage function curve) were used for estimating the flood damage. The flood depth and areal extent were obtained from flood modeling and mapping using HEC-HMS/RAS and Arc GIS, respectively. Expected annual damage (EAD) for residential areas (50,112 units) and commercial areas (9,318 premises) were RM12.59 million and RM2.96 million, respectively. The flood hazard map shows that Bandar Seberang area (46,184 properties) was the most affected by the 2011 flood. The flood damage map illustrates similar patterns, with Bandar Seberang suffering the highest damage. The damage distribution maps are useful for reducing future flood damage by identifying properties with high flood risk. HIGHLIGHTS In developing countries, literature on flood vulnerability assessment are limited especially on flood damage. Nowadays, vulnerability is considered as important as hazard.; The paradigm shifts from the conventional to a risk-based approach focus more on generating flood risk map instead of flood hazard map. However, the type of maps that includes the consequences of flooding has yet to be satisfactorily developed by most of the developing countries including Malaysia which still depend on hazard maps, while a risk map that illustrated the risk of flooding in terms of monetary is rarely available.; Hence an attempt have been made to develop flood damage map showing the impact of flooding in monetary term. The novelty of this research is the estimation of flood damage for an urban area in Malaysia using a site specific damage curve. As the study on flood vulnerability assessment are limited, these frameworks also serve as useful guidelines to initiate flood risk management practice in Malaysia, especially in producing a risk map showing the expected damage in monetary terms.;

Keywords

• commercial
• flood damage curve
• flood damage map
• malaysia
• residential