Application of Multi-parametric AHP for Flood Hazard Zonation in Coastal Lowland Area of Central Vietnam

Abstract

Flooding is one of the most commonly occurring natural hazards worldwide. Multiple geomorphic factors such as elevation, slope, topographic wetness index and distance from the river channel impact on flood susceptibility. Determining the effect of each factor and integration of their influence on flood hazard zonation has become an essential need in flood management. This study attempts to develop a hierarchical model for flood hazard zonation in the coastal lowland of Central Vietnam by using a multi-parametric approach. Five factors including elevation based flood inundation, distance from the river channel, land use, slope and topographic wetness index have been taken into consideration for developing flood hazard zonation. The Analytical Hierarchy Process (AHP) method was applied to assign weights according to the pair-wise comparisons of the parameters. These weights were used for calculation of Flood Hazard Index which was then evaluated and classified into four zones of flood hazard susceptibility. The result of flood hazard zonation was compared with field survey flood pillar points and flood inundation map extracted from ALOS PALSAR image in 2007 for validation. The comparison with field flood pillars indicated good correspondence with demarcated zones and estimated depth. Further, nearly 80 percent of inundated areas observed in ALOS PALSAR data fall in the high and very high flood hazard zones. The excellent agreement between flood hazard zonation map and observed inundation demonstrate the effectiveness AHP based method in flood hazard assessment.