Geographia Technica, Vol 15, Issue no.1/2020, pp. 16-26
GIS-BASED FLOOD HAZARD MAPPING USING HEC-RAS MODEL: A CASE STUDY OF LOWER MEKONG RIVER, CAMBODIA
Vanthan KIM, Sarintip TANTANEE, Wayan SUPARTA 
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ABSTRACT: Rivers are the main water sources for human and animals’ lives. Unfortunately, they have been frequently damaged by flooding. Flooding has affected and threatened not only human’s lives and infrastructures but also the environmental capital. This study aims to determine the application of flood frequency analysis integrated with the GIS and HEC-RAS models to prepare a multi-return period flood hazard map in the Lower Mekong River of Cambodia. A 30-year peak discharge (Kampong Cham gauging station) with a multi-return period of 10, 20, 50, and 100-years was estimated by using four distributions analysis. An EasyFit software is used to test the best distribution for the input of the HEC-RAS model to prepare the estimation of the corresponding floodplain areas. The results showed that Log-Pearson III distribution analysis of the return period of 10, 20, 50, 100 years is the best fits with the 52,208 m3/s, 54,990 m3/s, 59,381 m3/s, and 62,194 m3/s, respectively. The HEC-RAS calibration indicated a good agreement with observed data discharge 2011 and 2013. While the simulation model shows the return period of floods 10 and 20 years for the predicted depth of flooding is stable compared to the flood peaks of 2011 and 2013 discharges, but the conditions of other flood return periods are not stable. Overall, HEC-RAS with its flood hazard map is a model that can estimate the level of flood depth in the Lower Mekong River, Cambodia and is useful in providing information about the depth and characteristics of floods for river communities.
Keywords: Flood Hazard Map, GIS, HEC-RAS, Flood Frequency analysis, Mekong River
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