Long-term bio-geomorphological modelling of the formation and succession of salt marshes

Abstract

The interaction between vegetation and the morphodynamics is considered to be an important process in salt marsh formation and succession. Therefore, the contribution of vegetation modelling on the long-term morphological development of salt marshes is assessed by implementing a vegetation growth model in the morphodynamic modelling software FINEL2d. It is found that the contribution of vegetation modelling depends on the type of system under consideration. Two types of systems have been identified, one in which vegetation is leading and one in which morphology is leading. For the situation that vegetation is leading, like in the sensitivity simulations, vegetation modelling is essential. In this type of system the vegetation growth determines the tidal creek pattern. On the other hand, when the vegetation follows the morphological development, as in the 'Saeftinghe' case, the contribution is less significant. This is reflected in the fact that there are minor differences in channel and tidal creek patterns between the bio-geomorphological simulations and the purely morphological model results. Nevertheless, the Saeftinghe case study results do demonstrate that the models can reproduce the development of channels, tidal creeks and tidal flats over a 100 year period, resulting in a BSS of around 0.8. Moreover, in general the results show that the bio-geomorphological models are capable of representing salt marsh characteristic morphological and hydrodynamic phenomena, i.e. overgrown marsh platform dissected by tidal creeks, realistic flow velocities and characteristic erosion/sedimentation patterns.