EROSION OF VEGETATED COASTAL DUNES

Abstract

Coastal dunes can protect communities and infrastructure against storm surge and wave attack. They provide a natural barrier of granular material that erodes during storm conditions and dissipates wave energy in the process. Vegetation is abundantly present in most coastal dunes and may enhance the capability of the dune to withstand erosion. However, reliable data allowing quantification of the erosion process of dunes are sparse, in particular, data involving live plants. In this study, physical model experiments in a moveable-bed wave flume were carried out to investigate the effect of live plants on the wave-induced dune erosion process. The dune grass Sporobolus virginicus was grown in pots with dune sediment, transplanted into test dunes and subjected to both regular and irregular wave attack. Measurements of hydrodynamics and profile evolution show that the vegetation does affect the eroded dune volume and the dune scarp retreat rate. During wave flume testing vegetation density ranged from 0 to 80 plants per square meter and plant maturity (i.e. age) was varied between 0 and 12 weeks but further tests are necessary to substantiate the observed trends. The maturity of the plants' root system yielded the most significant impact on dune erosion as plants with more developed roots were able to reduce the eroded dune volume more than plants with less mature root systems.