How to account for flexible aquatic vegetation in large-scale morphodynamic models

Abstract

Worldwide, aquatic vegetation is important for the physical and ecological condition of coastal areas. Unfortunately, this vegetation (e.g. seagrasses) is also under pressure due to human activities. Protection and restoration are cumbersome, particularly because the complex relations between vegetation and its environment are not yet well understood. One of the key characteristics of aquatic vegetation is its flexibility, causing the plants position and drag to vary in time. The model presented in this paper, a combination of the detailed process-based hydrodynamic/plant motion model Dynveg and the large-scale morphological model Delft3D that deals with rigid vegetation, can be useful in studying some of these relations. By choosing the height and the drag coefficient of the rigid objects equal to that of the flexible plants under similar conditions, the flow pattern is analogous. The applicability of this modelling approach is demonstrated by comparing model results with flume experiments on the seagrass species Zostera noltii.