Evaluation and validation of flood hazard zoning using Analytical Hierarchy Process and GIS: A case study of Lam River basin (Vietnam)

In recent years, the Lam river basin has suffered various forms of natural disasters such as floods, inundations, windstorms, tornadoes, etc. Among all these, the flood has proved to be the greatest threat to the people and the socioeconomic development in the basin. Moreover, it is very frequent as compared to other natural disasters. In view of the fact that such disastrous floods still occur in the basin, it becomes a necessity to determine the causes and analyze the components affecting flooding. This is important in order to develop an early flood warning system and thus minimize the negative impact of floods in the Lam river basin on the people and the facilities. In this paper, the analytical hierarchy process (AHP) analysis method integrated with GIS technology is used to map flood risk zones in the Lam river basin. The parameters used for the analysis are the main causes affecting the floods. In addition to the five most commonly used factors such as slope, rainfall, land cover, soil, and drainage density, this study also includes a new factor - relative slope length - to compute a more rigorous and reliable model. The results were compared with two more methods of flood hazard zoning in the same study area: the method of analyzing the main cause of the flood, and the method of inheriting, data analyzing, and processing. The results were also validated by the historical flood data of three years: 2010, 2013, and 2016.