The effect of water level rise on coastal wave Overwash and Inundation of dunes in laboratory

Abstract

Beach responses to sea level rise are investigated experimentally in laboratory wave flume by detecting the beach profile continuously using video cameras in high space and time resolution. Experiments are conducted to discuss the profile response in three scenarios of water level rise: a step-change in water level, continuous water level rise as well as extremely high water levels to find out the intensification and dissipation of swash motion waves in overwash and inundation hydrodynamic and the retreat of the shoreline due to water level rise. The sediment transport rates are estimated from the detailed monitoring of the beach profiles, from which the responses of the shoreline to the water level rise are examined.The morphological characteristics of the dunes caused by sea-level rise are discussed and it is noted that sea-level rise leads to an increase of more than 40% in sediment loss from sand dunes, while extreme solitary wave conditions are less affected by water level changes. The characteristics of shoreline retreat for different sea levels and wave conditions are analyzed from the experiment data. The developments of shoreline and beach response prediction model using the laboratory experiment data to the sea level rise are discussed for better estimation of the shoreline change to the sea level rise. Meanwhile, the trend of wave energy is consistent with the frequency of profile change as the water level continues to rise. When the water level is high enough close to the dune crest, partially broken waves in nearshore areas transmitted landward with large wave energy quickly destroy the dunes, which is a great threat to the beach ecosystem. There is an inhibitory effect on the morphological changes of the dunes as the water level is high in the back of the dunes.