Flow patterns in partially vegetated channels

Abstract

As coastal wetland ecosystems, thriving at the interface between land and water,
mangroves can benefit us in lots of ways: providing food and timber, purifying water and sequestrating carbon, protecting coastal area through wave attenuation and coastal stabilization. Regarding the protection of coastal area, mangroves damp the flow in short term and mitigate coastal erosion in long term.
In mangrove forests, the capability of mangroves to capture sediments leads to
accumulation of sediments within the mangrove forests. Hence, the elevation of the floodplain, where the mangroves grow, is usually higher than the main river bed. The slope connecting the main river channel and floodplain has been found with different angle. The topography of the mangrove area is influenced by both sediment dynamics and hydrodynamics. The physical processes behind this is still not fully understood. This study aims to study the hydrodynamics in a partially vegetated compound channel by using the 2DH RANS model in Delft3D and to verify to what extend the flow characteristics can be reproduced. The reference numerical model is set up to mimic the flume experiments so that the model can be calibrated. The influence of different physical and environmental parameters on flow characteristics is studied. Also, the limitation of Delft3D in simulating the flow in a partially vegetated compound channel has been found.