Morphodynamic Modeling of the Song Hau (Mekong) River Channel in Vietnam

A reduced complexity, integrated compartment model (ICM) and a fully dynamic model (Delft3D) are applied to the lower Mekong River. The intent of this modeling effort is to improve our understanding of the hydrodynamics, sediment transport and morphodynamics in this tide-dominated deltaic system. The ICM is a planning-level numerical tool. It simulates hydrology, sediment transport, morphology and vegetation for large spatial domains, over long-term periods with high computational efficiency (run time of 10’s of hours for a 50-year simulation), providing valuable insights into the long-term changes to the system. Delft3D is capable of simulating detailed hydrodynamics, sediment transport and morphological changes of the delta. Both models were developed using high-resolution bathymetry data of the Song Hau channel, and are being validated with hydrodynamic and sediment dynamics data collected during field excursions in 2014 and 2015. The models, integrated with the field observations, will be used to develop sediment budgets (for both sand and fines) at the seasonal and annual scales. These budgets will improve the understanding of the sediment flux to/from the coastal ocean and the exchange of sediment between the channel bottom and water column. These tools will also be used to quantify the sediment flux to the mangrove area at the land-sea interface. The models will provide these insights at various spatial scales ranging from meters to kilometers and temporal scales from flood/storm events (days) to decadal. Such insights would improve our understanding of the deltaic systems in terms of their present development/evolution, and their response to plausible subsidence and sea level rise future scenarios.