Magazine Geodesy - Cartorgraphy

Study on the Impact of Sediment Decline on Morphological Changes of the Tiền River and Hậu River

Abstract

In this study, we employed the TELEMAC-2D hydrodynamic model coupled with the SISYPHE sediment transport module to simulate sediment dynamics and riverbed morphodynamic changes of the Hau River over the period 2014–2017. The results show that suspended sediment concentrations (SSC) during the flood season are approximately four times higher than during the low-flow season. Along the river reach, SSC declines progressively from Chau Doc toward Can Tho during the flood period, whereas in the low-flow period the change in SSC longitudinally is minimal. Notably, SSC levels from Chau Doc to the Vam Nao confluence are relatively low compared to the adjacent branch (Tien River), but abruptly increase just downstream of the junction, consistent with the transfer of about 40–50 % of the Tien River’s sediment load. Modelled bed changes indicate predominance of scour over deposition on the Hau River: an average scour depth of –0.68 m corresponds to a mean annual scour rate of –0.23 m/year. Forecasts to 2026 suggest severe bed lowering and formation of deep scour holes, many of which coincide with bank-erosion hotspots. These findings underscore that bed lowering is strongly linked to bank instability and highlight the urgent need for management measures to mitigate bank-erosion risk.