Coastal wetland response to sea-level rise: migration and flow attenuation affect their accretion capacity.

Abstract:

The response of wetland vegetation communities depends on a range of factors including the rate of sea level rise and the rate of surface elevation change due to wetland eco-geomorphic accretion. If wetland accretion is unable to match sea level rise and relatively steep landward topography precludes their landward transgression, coastal wetlands may be completely submerged. Vegetation migrates according to preference to hydrodynamic conditions which can be described as a function of local values of inundation depth and hydroperiod. Eco-geomorphic accretion also depends on inundation conditions. Vegetation roughness in tidal flats reduces depth and maximum inundation extent but increases ponding, so it affects both inundation depths and hydroperiods. Local man-made flow restrictions in tidal flats and channels also affect flood attenuation. By using numerical simulations, we demonstrate in this contribution that the effect of flow attenuation and migration effectively reduce the accretion capacity of coastal wetlands, making them less resilient to sea-level rise.