304 / 2024-02-29 12:56:44

PARAMETER OPTIMIZATION OF HYDROLOGICAL MODEL FOR MULTIPLE FLOOD EVENTS BY SCE-UA AND COMBINATION OF EVALUATION FUNCTIONS: A CASE STUDY IN YAMATO RIVER, JAPAN

Optimization,RRI model,SCE-UA,Multiple evaluation functions,Parameter optimization

Climate change is causing a trend toward more torrential rains with strong rainfall intensity, which increases the risk of flooding. In particular, more accurate prediction of river discharge is needed for flood forecasting in rivers. This study used the Shuffled Complex Evolution method developed at The University of Arizona (SCE-UA) method to evaluate the parameters of the Rainfall-Runoff-Inundation (RRI) model, which is one of the distributed runoff models for torrential rainfall.

In general, distributed runoff models have many parameters, and it is difficult to optimize parameters for various rainfall patterns. This study aims to propose procedures for optimizing parameters for multiple intense rainfall events with relatively short flood arrival times in the Yamato River basin, Japan. First, the parameter optimization of each evaluation function was performed as a single optimization; the model performance with optimized parameters was a slightly good. The single evaluation function tended to fit to one of the rainfall patterns, not to multiple rainfall wave patterns, because of the characteristics of each evaluation function. Therefore, we introduced a combination of evaluation functions and then optimized the parameters for multiple rainfalls. The combination of evaluation functions improved the accuracy of river flow forecasting more than the optimization of parameters for a single evaluation function. Among the combinations of evaluation functions, the combination of peak error, squared error and correlation coefficient showed better performance of the peak flow rate and the combination that included RMSE in the peak error produced better overall waveform.In this study, the parameter optimization in the case of simple torrential rainfall showed good results. Additional studies on the applicability of the method of combining evaluation functions for parameter optimization in more complex rainfall waveforms are considered necessary.