Modified geomorphic flood index (GFI) using land use parameter and effective rainfall ratio at Cikapundung River

Abstract

To determine the flood inundation area requires hydrological data and measurements of river cross sections. Those data are very limited and expensive. The Geomorphic Flood Index (GFI) can be used to identify the initial potential for inundation of an area. Until now, the GFI method only uses Digital Elevation Model (DEM) data and the return period cannot be known. GFI is then modified by using topographic, rainfall and land use maps to determine the potential flood inundation for each return period. Based on the results of the GFI analysis with an n value of 0.31, the result of flood inundation is quite close to the hydraulic approach with a return period of 100 years. To find out the inundation of floods in other periods (2 years to 50 years), it is necessary to modify the GFI by entering the weight in the analysis of the flow accumulation. The results of the modified GFI flood inundation show that the smaller the return period, the lower the flood height and the reduced flood inundation area in the affected areas. Thus, the GFI approach is still good enough for initial estimates in determining flood inundation with quick analysis and lower costs.