Flood hazard comparison based on geomorphic flood index and hydraulic HEC-RAS (Case study in Ciliwung Watershed, Jakarta)

Abstract

Abstract The Jakarta Special Capital Region is a highly vulnerable area to floods due to its location on wetlands laced by 13 major rivers and borders the Java Sea, with more than 40% of its land below sea level and groundwater extraction leading to the ground sinking. The city has experienced several major flood disasters, and climate change has increased the risk, frequency, and severity of flooding in Jakarta. The present study aims to identify areas with flood potential in the Jakarta Special Capital Region (Provinsi DKI Jakarta) using the Geospatial Flood Index (GFI) method recommended by the National Disaster Management Agency (BNPB). The GFI method is an alternative rapid assessment that utilizes the Digital Elevation Model for National Spatial (DEMNAS) data with an 8-meter spatial resolution and employs ARCGIS and QGIS software to identify areas with high potential for flooding and the extent of inundation. To assess the effectiveness of this method, a comparison is made with the Hydraulic HECRAS model for the section from the Automatic Water Level Recorder (AWLR) MT. Hartono to the Manggarai Flood Gate, considering flood return periods Q50 and Q100. The modeling results indicate that the inundation area estimated by the conventional GFI modeling is 150% larger than that the HECRAS Hydraulic model predicted.