Rough bottoms: the effect of bed roughness on waves in coastal wetlands
Coastal wetlands are increasingly seen as important landforms acting to protect landward lying environments from high water levels and waves during storm surges. The physical process mechanisms by which such protection is provided are complex, as hydrodynamic energy is transformed by interaction with a variety of inundated surface elements (topographic features and vegetation canopy). Resolving those mechanisms in process-based numerical models remains a key and fundamental challenge within this field of research. Overcoming this challenge, however, is necessary if coastal wetlands are to be successfully included in coastal flood and erosion protection scheme designs.
This talk presents the results of many years of measurement of wave transformation across varied wetland surfaces in the field and the laboratory. These observations offer interesting insights into the variability of wave dissipation by rough wetland beds and allow, at least conceptually, an understanding of the characteristics of wetland surfaces that must be quantified to achieve a better representation of bed roughness in hydrodynamic models. Potential methods for such quantification are presented and discussed, as is their possible incorporation into hydrodynamic models (with a focus on the general principles and landform-scale considerations, rather than technical modelling challenges).