An investigation on salt marsh resilience to sea-level rise and increased storm intensity

Abstract

Salt marshes are ecosystems with significant economic and environmental value. They provide numerous services, including nutrient removal, habitat provision and carbon sequestration (Barbier et al., 2011). They are also widely recognised as nature-based solutions for coastal defence due to their ability to buffer storm waves (Leonardi et al., 2018). However, it is still unclear how the combined impact of future sea-level rise and possible increases in storm intensity will affect salt marsh resilience (Schuerch et al. 2013). It has been observed that salt marshes can survive sea-level rise if sediment supply and organogenic production are high enough to allow marsh accretion (Kirwan et al., 2010, 2016). However, increasing rates of sea-level rise can lead to marsh drowning by increasing the accommodation space and the amount of sediment inputs required for marsh stability (Kirwan et al., 2010; Ganju et al., 2017). Marsh degradation can also be caused by lateral erosion triggered by wind waves, such as the ones generated during storms (Leonardi et al., 2016; Li et al., 2019). However, several studies have showed that, on the other hand, overwash by storm surges can support marsh resilience by delivering significant amount of sediment to marsh platforms (Walters and Kirwan, 2016; Castagno et al., 2018). 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 survival and accretion of salt marshes, while a negative sediment budget causes marsh degradation (Ganju et al. 2015). The Ribble Estuary, North-West England, was used as a case study.