Presenter: Rae Taylor-Burns (UC Santa Cruz; US Geological Survey)

Description:
Understanding wave transformation in estuarine settings is critical to assess the influence of vegetation on wave dissipation, and to inform tidal marsh restoration practices designed to mitigate flooding along estuarine shorelines under the pressures of sea level rise. To test wave transformation across a variety of vegetated settings, a numerical model, XBeach non-hydrostatic, was calibrated and validated with high frequency pressure data from the marsh at China Camp State Park, in San Francisco Bay, CA (USA). Previous studies have determined that wave height decay across vegetation fields depends on variables including water level, vegetation height, wave height, and frictional coefficient. However, other aspects of marsh morphology, such as elevation, slope, and width, have not been considered, and interactions between these variables have not been investigated. This study examines the role of vegetation in reducing flooding, assesses which characteristics of marshes control wave attenuation and flood reduction, explores how these characteristics interact, and investigates how the capacity of marshes to reduce flooding may change with higher water levels and larger waves. In the range of model settings explored here, vegetation on a marsh routinely reduces wave height by 35 cm, and in extreme settings can reduce wave runup by up to 130 cm. Likewise, in the range of model settings explored here, vegetation on a marsh routinely reduces wave runup by 40 cm, and in extreme settings can reduce wave runup by up to 150 cm. This benefit can be achieved even in the narrowest marshes simulated.