Ideal vegetation height maximizes sedimentation in freshwater deltaic marshes during flood

River deltas are complex environments affected by the morphodynamic interaction between flow and sediment transport. This morphodynamic interaction is potentially affected by the freshwater marsh vegetation (e.g. sagittaria and typha) on the exposed surfaces of emergent deltaic islands. As a first step, we present modeling results and remote sensing data on how vegetation affects sedimentation within deltaic islands. Our modeling starts from a pre-formed river delta configuration and then we populate it with different vegetation with different height characteristics. We then subject the delta to floods of varying magnitudes to evaluate how vegetation affects sedimentation during a flood. In our numerical experiments vegetation height affects sedimentation in two key ways. Increase in vegetation height causes a non-linear decrease in sediment flux on to the islands (up to 80% when compared to the case without vegetation). On the other hand vegetation slows water velocity and lengthens the residence time of a water particle up to 50%. Even though vegetation reduces the sediment flux onto the islands, the increase in residence time traps more sediment resulting in higher island sedimentation rates when vegetation is present. Interestingly, we find that an intermediate vegetation height that maximizes island sedimentation rate. This occurs because sediment flux exiting the islands decreases faster (due to increase in residence time) than the sediment flux entering the islands. Finally we analyzed the spatial and seasonal evolution of the vegetation on Wax lake delta, Louisiana through the normalized difference vegetation index (NDVI). We find that NDVI varies seasonally as vegetation grows and dies, suggesting that the timing of the arrival flood wave relative to vegetation height is a critical parameter that for predicting sedimentation of deltaic islands.