GEOMORPHOLOGY AND INUNDATION BEHAVIOR OF THIRTY CRITICAL WATERSHEDS IN MINDANAO

摘要

The geomorphology of the watershed characterizes the formation of the river flood plains as it plays key roles on the dynamic hydrologic behavior in relation to flooding. To determine the extent of geomorphologic impact on the percent coverage of inundated area within the floodplain, this study analyzed 30 rivers across Mindanao with majority identified as critical base on the impaired biotic and biotic status due to socioeconomic roles and susceptibility, and potential threats to flooding by the Mindanao Rivers Reconstruction Task Force (MMRTF). Using ASTER Global DEM (ASTGTM) 30m Digital Elevation Model (DEM), watershed boundaries and river networks were determined using ArcGIS of Esri. Inundated areas of each watershed were likewise delineated based on the Mines and Geosciences Bureau (MGB) Maps. Regression analysis was conducted between inundated areas and the various geomorphologic values such as basin size, form factor, elongation ratio, circularity ratio, length of overland flow, basin relief, slope, number of stream, stream order, stream frequency, and stream density among others. Results revealed that inundated area is explained by the geomorphologic attributes of the watersheds. This implies that geomorphologic features of watershed are good indicators of flood prone zone within the landscape. Awareness on the geomorphologic characteristics of the watershed is helpful to the disaster risk reduction management council both at the local and national level particularly in prioritizing areas which need preventive mitigation measures and relief goods distribution for cost effective and efficient management operations.