Vegetation promotes flow retardation and retention in deltaic wetlands

Abstract

We introduce a new approach to observe the impact of vegetation on tidal flow retardation and retention at large spatial scales. Using radar interferometry and in situ water level gauge measurements during low tide, we find that vegetation in deltaic intertidal zones of the Wax Lake Delta, Louisiana, causes significant tidal distortion with both a delay (between 80 and 140 min) and amplitude reduction (~ 20 cm). The natural vegetation front delays the ebb tide, which increases the minimum water level and hydro-period inside the deltaic islands, resulting in better conditions for wetland species colonizing low elevations. This positive feedback between vegetation and hydraulics demonstrates the self-organization functionality of vegetation in the geomorphological evolution of deltas, which contributes to deltaic stability.