Flood Disaster Investigation Based On Correlation Of Quantitative Geomorphology And Groundwater Level In Cintaratu Village, Pangandaran Regency, West Java Province, Indonesia

Recently, a flood disaster is occurred in Cintaratu Village, Parigi Sub-district, Pangandaran Regency of West Java Province. Geomorphologically, the watershed systems of this area consist of Cintaratu, Selasari dan Cintakarya. Geologically, the study area is composed by calcarenite, reef limestone, and clastic limestone which is susceptible to dissolution when contact with the water. This research was conducted to investigate the causes of flood disaster based on the correlation between quantitative geomorphology and groundwater level analysis. The methods for this research are field observation and studio analysis. Field observation were conducted by hydro-geological mapping to determine the groundwater level and, also, the lithology of the surrounded area. Studio analyses include the calculation of Bifurcation Ratio (Rb), Drainage Density (Dd), and Fault Fracture Density (FFD). Based on Bifurcation Ratio calculation, the value of Rb1-2 of Cintaratu, Selasari, and Cintakarya Watershed respectively are 2.8, 6, and 3.5. Generally, Cintaratu Watershed has the lowest Rb value, and thus has the highest potential to be flooded. Groundwater flow map shows that the stream accumulation zone is located at the center due to topography controlled, thus allows water to accumulate. The average elevation of groundwater is is 111.3871 masl, however, the the average elevation of the ground is 117.4706 masl. The difference of both value is 6.083529 m. This shows that undersaturated area between groundwater elevation and ground elevation is low. So it can be concluded that, the main causes of flood disaster either from above or underground can be investigated by the correlation between quantitative geomorphology analysis and groundwater level.