Rainfall-runoff Modelling of Amochu Basin in Bhutan using HEC-HMS Model with Remote Sensing and GIS-based Parameterization

Abstract

Modelling surface runoff of a basin is important for integrated water resource management, planning developmental activities, flood mapping and zoning, safeguarding human lives and building resilient flood protection structures downstream. The low-lying plain of Amochu basin is no exception to flood and natural disaster. Recurrent floods have led to loss of life and property. HEC-GeoHMS and HEC-HMS models were applied to generate and simulate river runoff from daily precipitation fusing in with other basin parameters. The input parameters for rainfall-runoff modelling were carried out effectively by using GIS and Remote Sensing techniques. application of Remote. The simulation analysis of rainfall-runoff model combines soil conservation service-curve number (SCS-CN) for loss calculation, SCS Unit Hydrograph for transformation and Muskingum methods were implemented for routing of flow. The streamflow stimulated using HEC-HMS model were analysed and compared with the existing observed streamflow data. The model efficacy was evaluated using Nash-Sutcliffe Efficiency Coefficient (NSE) and Root Mean Square Standard Deviation (RMSE). For the annual time series (January-December), the average values of NSE were 0.68 and 0.64 for calibration and verification, correspondingly. For the seasonal time series (June-September), the model achieved average NSE value of 0.66 and 0.65 during calibration and verification, respectively. The association of streamflow from model simulation verified satisfactory agreement with the detected streamflow values during both calibration (R2=0.6) and validation (R2=0.6). The average area weighted Curve Number (CN) derived from 11 sub-basins of Amochu was 75.7