MODELING EFFECTS OF VEGETATION ON SETUP AND RUNUP OF RANDOM WAVES

Abstract

The effects of coastal vegetation on wave attenuation have been well acknowledged and quantified. However, the studies on the effects of vegetation on wave setup and runup are still limited. Wave setup contributes to the elevated water level during a storm event. Flume tests (Wu et al. 2011) show that vegetation reduces the wave setup and neglecting vegetation will overestimate the mean water level (MWL). Dean and Bender (2006) theoretically examined the MWL change in vegetation. van Rooijen et al. (2016) numerically studied the effects of vegetation on wave setup using a storm impact model, XBeach. The wave-averaged drag force (𝑓𝑣̅) in XBeach was obtained through a wave shape model based on stream function wave theory. This wave shape model was calibrated with field data collected at barred beaches without vegetation, and thus may not be applicable to vegetated shorelines. The objective of this study is to model the effects of vegetation on the setup and runup of random waves using a cross-shore numerical model (CSHORE; Kobayashi et al. 1998). A new parametric model is proposed to compute 𝑓𝑣̅ in CSHORE. Effects of vegetation on wave setup and runup are examined through numerical experiments.