Hydrodynamic characteristics of flood flows in bifurcations: A case study of the Hong – Duong birfucation

Abstract

In the present paper, the model namely MIKE 21FM is applied to simulate velocity, water elevation and
discharge of flood flows in the Hong - Duong bifurcation. Daily flows in the flood season of 2014 and
2018 are used for sensitive analysis, parameters calibration and model validation. The results showed
that root mean square error (RMSE) and mean absolute error (MAE) of water elevation at Ba Giang,
Lien Mac, Ha Noi, Xuan Quan and Thuong Cat change from 1.5 to 7% of observed magnitude at the
stations, while correlation coefficient (r) and Nash-Sufficient coefficient (NSE) close to unity for both
calibtation and validation steps. Indeed, RMSE and MAE of water discharge at Ha Noi and Thuong Cat
equal only about 6% of observed magnitude, while r and NSE is greater than 0.84. Simulated results of
historical floods occurred in 1971 and 1996 also depicted that flow velocity varies between -1.5 and 4.5
m/s. The percentage of water discharge moving from the Red to the Duong River for two
aforementioned flood events is about 30% of water dischage before the bifurcation.