ABSTRACT

The present work investigates the evolution process of beach nourished profile with a permeable submerged breakwater based on a physical experiment. A series of test cases with different configurations of the submerged breakwater in installation position, width and submerged depth are conducted in a wave flume, which acquire the time series of free surface elevation and beach profile elevation. The spatial variation of wave hydrodynamics, beach behavior and morphological characteristics during the evolution of nourished beach profile are investigated. The effect of offshore distance, crest width and relative submerged depth of the permeable submerged breakwater on beach erosion is discussed. The results show that the submerged breakwater with a bigger crest width in the middle position has the better protection effect for preventing beach erosion, while the absolute wave height or relative submerged depth plays a dominant role in different cases.

INTRODUCTION

Sandy beaches are suffering serious erosion under the combined action of the negative environmental impact caused by human activities and global warming. With the continuous improvement of marine ecological protection awareness, the beach restoration technology of soft protection or combination of soft and hard has attracted more attention. As a new type of permeable structure, permeable submerged breakwater leads to additional energy dissipation caused by porous media, whose safety and ecology are comparable to those of traditional dense submerged breakwater. In addition, it has been widely used due to its lower construction cost and longer service life.

In recent years, extensive research have been carried out to reveal wave interactions with permeable submerged breakwater. The propagation of waves over permeable submerged breakwaters and detailed velocity fields around and inside the obstacle has been widely studied through numerical and physical model tests (Wu et al., 2013; Ma et al., 2014; Pourteimouri and Hejazi., 2020).

Numerical simulation has been used to simulate wave hydrodynamics and cross-shore sediment transport. Through physics based formulas and simple diagrams of the governing processes, a model was proposed to simulate the evolution of longshore sandbars and the material exchange between the berm and sandbar, and calculate dune erosion, over-wash and wind-blown sand to model the evolution of a schematized profile at a decadal scale (Larson et al, 2013; Larson et al, 2016).

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