The effect of evaporation on the erodibility of mudflats in a mesotidal estuary

Large areas of mesotidal estuaries become subaerial during low tide. Here we study the effect of several meteorological and hydrodynamic parameters on the erodibility of mudflat substrates when they are subaerial. Field measurements carried out over a two-week period in September 2011 in Plum Island Sound, Massachusetts USA, indicate that high evaporation rates and long subaerial periods are associated to low sediment erodibility. Sediment concentrations in the water column during submergence depend on bottom shear stresses triggered by tidal currents. Surprisingly, they are also related to the total evaporation that occurred in the previous emergence period. We conclude that low erodibility of mudflat sediments is linked to subaerial desiccation at low tide. This strengthening effect is not lost during the following submerged period, thus limiting the erosive effect of tidal currents. We thus show that not only subaqueous but also subaerial processes might control the erodibility of mudflats. Long-term evaporation rates can therefore directly affect the stability of mudflats in mesotidal environments. (C) 2017 Elsevier Ltd. All rights reserved.