Adding wave energy to a model simulating salt marshes to study and visualize marsh protection against sediment erosion by placement of barriers.

Abstract

Salt marshes are important ecosystems, providing important services to society. Many are however declining in size due to the impact of human activities in estuaries. One example of such an impact is a change in the balance between sedimentation and erosion in the Oosterschelde due to the presence of a storm surge barrier, which has led to ongoing erosion of the salt marshes in the Oosterschelde basin. In this study a model that simulates salt marsh development was adapted to investigate whether and how wave barriers could counter the erosion of salt marshes. For this, the model was expanded with a wave model. Wave energy was found to interact with every aspect of marsh development ranging from sedimentation to vegetation growth. An increasing cover of the marsh by wave barriers had a non-linear effect in reducing wave impact leading to increased marsh development. This highlights that a partial cover of the marsh by barriers provided sufficient wave protection, and increase heterogeneity of the landscape and of biomass, which could optimize niche variability and hence biodiversity. Grazing of marsh vegetation resulted in lower creek complexity. It is hypothesized that this is because vegetation traps less sediment leading to increased topographic smoothing, reducing habitat heterogeneity. The size of barriers could be of importance considering marsh restoration as a large coverage of the marsh by barriers resulted in lower biodiversity and flow rate. This study highlights the potential of wave barriers to prevent marsh erosion as well as manage habitat complexity, facilitating a diverse marsh community.