HYDRODYNAMIC MODELING FOR FLOOD HAZARD ASSESSMENT IN TELOMOYO CATCHMENT, CENTRAL JAVA, INDONESIA

Flooding is considered as one of the most devastating events in many parts of the world. In terms of its frequency and distribution, river flooding remains as a frequent disaster that has to be faced by civilization in the floodplain. Due to the periodical occurrence and adverse impact that may be generated, flood risk management is necessary to conduct. Flood hazard assessment is the preliminary step in conducting the flood risk management. A coupled 1D2D hydrodynamic modeling has become a popular practical method in flood hazard assessment due to its advantage in predicting the flood events which did not occur in history. This modeling helps to understand the flood hazard and serves a tool which also useful in understanding the effect of mitigation measures. The flood model was based on four different retun periods (2 yr, 5 yr, 10 yr, and 25 yr). Digital elevation model (DEM) is substantially important in conducting such flood model. Geostatistical analysis was preferred to do DEM generation. Three interpolation methods were used in this study and the results were compared. The Simple Kriging was the best geostatistical predictor since it embedded the least SD, RMSE, and unbiased interpolation. The result of the flood model showed that the flood, either from low magnitude (2 yr) and high magnitude (25 yr) only inundated 15% of the study area. The positive relationship of the inundation area and flood magnitude was identified. The comparison of the flood model and the observed data in term of the flood depth showed 35 cm differences. The DEM error interpolation by 31 cm propagated in the flood modeling and doubled the error of the flood depth by 64 cm