Abstract
Flooding is one of the major destructive natural disasters in Davao Oriental, Philippines, and results primarily from a high incidence of typhoons and heavy rainfalls. The main objective of this study was to identify flood-prone risk areas by mapping them based on the integration of multiple indicators, including rainfall, slope, elevation, drainage density, soil type, distance to the main channel and population density. For this purpose, a GIS-based flood risk spatial assessment was conducted by using analytic hierarchy process (AHP), weights by rank (WR) and ratio weighting (RW) frameworks to determine the relative importance of each indicator against another in the province of Davao Oriental. The resulting flood-prone areas by the three methods are validated by comparing with the estimated flood map based on ground truthing points from a field survey. The comparison results show that AHP is the most appropriate method among them to assess flood hazard. The result of the AHP flood risk map shows that 95.99% (5451.27 km2) of Davao Oriental is under low and moderate flood risk. The high and very high flood risk area covers approximately 3.39% (192.52 km2) of the province, primarily in the coastal areas. Thirty-one out of the one hundred eighty-three (31/183) barangays (towns) are at a high to very high risk of flooding at current climate, calling for the immediate attention of decision-makers to develop mitigation strategies for the future occurrence of flooding in Davao Oriental.
Highlights
Flooding is considered one of the most serious and widespread natural hazards due to its devastating effects that endanger lives and cause property damage in the affected areas [1,2,3,4,5,6].The changing climate behavior of extreme rainfalls and typhoons are the primary contributors to this problem
A geographical information system (GIS)-based flood risk assessment was conducted by using the concepts of analytic hierarchy process (AHP), weights by rank (WR) and ratio weighting (RW) frameworks in the province of Davao
The AHP model depicts a superior result in the computation of relative importance of indicators compared to WR and RW methods
Summary
The changing climate behavior of extreme rainfalls and typhoons are the primary contributors to this problem. Human activities such as urbanization and the growth of settlements and assets in flooding areas likewise contribute to the increasing impacts of floods [1,2,3,4]. The problems related to flooding have increased extensively, and there is a need for efficient modeling to help mitigate the worst effects of flood disasters [9]. Effective modeling will help in proper flood risk management planning and provides various insights into addressing the hazard and disaster problems. It is necessary to establish and implement a systematic approach to define areas that may have disastrous flood events
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