Fagherazzi (2014) - marshes & storms Flashcards
Coasts have become more vulnerable in recent decades as a consequence of…
Sea-level rise and, in some geographic locations, an increase in storm frequency and magnitude.
Salt marshes occur on shorelines in…
the intertidal zone and are dominated by salt-tolerant vegetation.
What poses the biggest threat to vulnerable coastlines?
Extreme storm events.
Storm surges can increase water levels significantly above the height of the marsh, causing waves to advance over the marsh towards the shoreline, resulting in less erosion at marsh boundaries than under non-surge conditions.
The evolution of the shoreline and its long-term resilience to coastal erosion is controlled by the type of defence — sandy beach or salt marsh — presented to extreme storm events…
The gentle slope of a sandy beach promotes the dissipation of small waves, but the loose sediments and the lack of root reinforcement allow the removal of large quantities of material during large storms.
Salt marshes effectively dissipate waves and mitigate coastal erosion during large storms. The vegetated surface can survive extreme wave conditions providing wave attenuation even after partial shedding of the canopy. Unfortunately, the evolution of shorelines guarded by marshland is dominated by the persistent wave erosion of normal weather conditions.
Marshes and sandy beaches also respond differently to increasing sea level as the climate warms.
Sea-level rise has a relatively limited effect on sandy beaches, causing beach profiles to simply shift inland.
On the contrary, accelerated sea-level rise can have a dramatic impact on salt marshes, including the drowning and collapse of the marshland if the vegetation growth cannot keep pace with the rising sea.
