Surface Wave and Roller Dissipation Observed with Shore-based Doppler Marine Radar

Abstract

The Earth's coastlines are facing sea level rise and increased human interventions. Predicting long-term coastal changes is of major importance to ensure efficient planning and design of coastal structures, as well as sustainable management of the coastal zone. Furthermore, a proper incorporation of nearshore processes into earth system models is required to efficiently predict the future changes of the coastal morphology, that is, coastal morphodynamics. Long-term measurements of nearshore hydrodynamics, in particular the spatial distribution of wave heights, are rarely available but often required to develop, validate, or calibrate parameterizations of nearshore processes.Breaking surface waves are important drivers of nearshore hydro-and morphodynamics. When a wave breaks, its height and thus the energy that is contained in the wave motion at the scale of the breaker decreases. The vast majority of the extracted wave energy is irreversibly converted (dissipated) to currents (slowly varying mean flow, e.g., Longuet-Higgins & Stewart, 1964), vorticity (Clark et al., 2012, turbulence (chaotic oscillations at higher frequencies, e.g., Feddersen & Trowbridge, 2005), heat (e.g., Sinnett & Feddersen, 2014), sea spray (Van Eijk et al., 2011), sound and air entrainment (Deane, 1997), and re-suspension of sediments (Voulgaris & Collins, 2000). Therefore, wave breaking and the associated wave energy dissipation link the wave energy flux to mixing and sediment transport. A "direct measurement of wave dissipation is equivalent to measuring the forcing for nearshore flow" (Holman & Haller, 2013). However, deployment and maintenance of in-situ sensors (e.g.,