Erosion Vulnerability Assessment in REINA, Quezon Province, Philippines with Raster-based Tool Built within GIS Environment

抄録

This study had developed a raster-based tool in order to automate the soil erosion vulnerability assessment. The tool that designed based on the empirical USLE (Wischmeier and Smith, 1978) was built using various available GIS geoprocessing tools. The data used in this study were prepared using Erdas Imagine and ArcGIS softwares. The cluster Municipalities of Real, Infanta and General Nakar (REINA), Quezon, Philippines were selected as study area as it was previously hit by strong typhoon that led to severe landslide and deluge in 2004. Damages to lives and properties were remarkably the biggest in the history of these Municipalities. Using the raster-based tool, erosion vulnerability was assessed. The results were categorized into six (6) classes. It showed that None to slight covers 33.42% of the total area while Very severe ranked second with 23.83%. Other categories were Moderate with (2.26%), High (14.05%), Very high (18.80%) and Severe (7.63%) respectively. Higher percentage of None to slight can be justified by the fact that the area is still having 47% dense vegetation. However, high percentage of Very severe was attributed to presence of hundreds of bare/eroded areas in the mountain created by landslide due to heavy rain during a disaster in 2004. The developed tool is believed to be useful in the current situation wherein the country is on the process of nationwide hazard mapping.