Vegetation wakes and wake interaction shaping aquatic landscape evolution

Abstract

Lay AbstractVegetation found in marshes and tidal systems influences the flow of water through these systems. Vegetation blocks the flow of water, leading to areas of low water velocity immediately downstream of a vegetation patch and areas of high water velocity at the sides of a patch. Areas of lower velocity provide good habitat for young plants and seedlings, and thus encourage plant growth such that the patch expands in the downstream direction. The addition of more vegetation near the original patch further reduces the local velocity that further promotes growth, creating a system of feedbacks. Recently, studies have found that when several patches of vegetation are near each other, they can change the shape and extent of the low‐velocity regions downstream. Based on these findings, the present study develops a model to evaluate how a field of vegetation might evolve over many years and the final distribution patterns that result. The model initially evaluates the water velocity based on a simple theoretical model and then modifies the velocity field to incorporate reduction of flow downstream of the patches, based on laboratory observations. Once the velocity at every point is calculated, vegetation is added probabilistically, with areas of high velocity having a low probability of growth and areas of low velocity having a high probability of growth. The number of initial vegetation patches and the limiting velocity (the velocity above which no plants can grow) were varied, and three different types of landscapes were produced: full vegetation coverage, channeled, and sparse. The effect of vegetation on the velocity field in the wake (i.e., downstream) of the vegetation is shown to accelerate landscape development.