Comparison of flood hydrograph prediction between synthetic unit hydrograph methods and rain-on-grid model for Katulampa watershed, Indonesia

In this paper, 6 synthetic unit hydrograph (SUH) methods, namely Snyder, SCS, GAMA-1, ITB-1, ITB-2, and Nakayasu, were compared against a rain-on-grid model (HEC-RAS) for flood hydrograph prediction in the Katulampa watershed, Indonesia. HEC-RAS was used with an open-access, ~30 m resolution digital elevation model (DEM), i.e. the Advanced Land Observing Satellite (ALOS). The relative error of the hydrograph results (peak discharge and time-to-peak) were compared with the observed data, while the errors in the hydrograph’s shape were detected using the Root Mean Square Error (RMSE) and Pearson Product Moment Correlation (PPMC). We found that HEC-RAS could predict the flood hydrograph significantly more accurately than the SUH methods, yielding the RMSE value of 1.98 m3/s and the PPMC value of 0.93. This study remains an interesting example of how modern computational tool can improve the runoff prediction of conventional SUH methods.