Salt marsh resilience to sea-level rise and increased storm intensity

Salt marshes are widely recognised as ecosystems with high economic and environmental value. However, it is still unclear how salt marshes will respond to the combined impact of future sea-level rise and possible increases in storm intensity (Schuerch et al. 2013). This study investigates marsh resilience under the combined impact of various storm surge and sea-level scenarios by using a sediment budget approach. The current paradigm is that a positive sediment budget supports the accretion of salt marshes and, therefore, its survival, while a negative sediment budget causes marsh degradation (Ganju et al. 2015). The Ribble Estuary, North-West England, was used as test case, and the hydrodynamic model Delft3D was used to simulate the response of the salt marsh system to the above scenarios. We conclude that the resilience of salt marshes and estuarine systems is enhanced under the effect of storm surges, as they promote flood dominance and trigger a net import of sediment.  Conversely, sea-level rise threatens marsh stability, by promoting ebb dominance and triggering a net export of sediment. Ultimately, when storm surge and sea-level scenarios are combined, results show that storms with the highest intensities have the potential to counteract the negative impact of sea-level rise by masking its effects on the sediment budget.

Acknowledgements

We acknowledge the support of the School of Environmental Sciences, University of Liverpool.

References

Ganju, N.K., Kirwan, M.L., Dickhudt, P.J., Guntenspergen, G.R., Cahoon, D.R. and Kroeger, K.D. 2015. “Sediment transport-based metrics of wetland stability”. Geophysical Research Letters, 42(19), 7992-8000.

Schuerch, M., Vafeidis, A., Slawig, T. and Temmerman, S. 2013. “Modeling the influence of changing storm patterns on the ability of a salt marsh to keep pace with sea level rise”. Journal of Geophysical Research-Earth Surface, 118(1), 84-96.