Modelling of hydrodynamic and erosion processes at vegetated lake shores

Abstract

In recent years, the interest in integrating shore protection with the local ecosystems has increased. In comparison with the traditional reinforced embankments, integrated shores form a gradual transition from land to water where shore vegetation can establish itself. These nature-friendly shores have a positive impact upon the water quality, flora and fauna and the amenities of the shore. Some of the benefits of vegetation are its capability of reducing the hydrodynamic loads on the shore and its ability to increase the soil strength against erosion. Both effects have been investigated in detail in previous research and have been implemented for coastal protection designs in sandy coastal settings. But a designing tool for cohesive shorelines in lake environments is still missing. In this research, the different aspects important for the erosion of a vegetated cohesive shoreline are studied and the first steps towards a process-based design tool are taken. The model results show that the dominant processes for erosion can be found at the point of wave breaking and at the start of the run-up, as both combinations give the highest induced bed shear stresses. This can be used for a strategic placement of vegetation to dampen the wave impact and reinforce the soil through the roots. There are situations in which a partially vegetated shore is sufficient to withstand the daily wave attack. This allows the vegetation to grow naturally to full strength, which is required in a storm situation. In this way a financial benefit can be reached as well as a healthier vegetated shore, as a large part of the vegetation has grown naturally.