Virginia Institute of Marine Science
JGR Earth Surface
Sand washed across barrier islands during storms (called overwash) provides sediment for salt marshes behind those islands, and can allow a marsh which otherwise would drown to grow vertically fast enough to keep up with sea level. We use a barrier island-marsh evolution model (GEOMBEST+) to see what effect marsh edge erosion by waves has on overwash-supported marshes. Consistent with previous research, we find that wave erosion can make marshes more resilient by freeing sediment that can be used elsewhere on the marsh surface. We add that horizontal erosion of the marsh edge provides more sediment per volume eroded than vertical erosion of the marsh surface. This is because the bottom layers of the marsh contain more sediment (that can stay on marsh surfaces), while the surface layers include plant material (that drifts away or decomposes). We also find that when the marsh and bay are keeping up with sea level, expanding or eroding the marsh is the only way to change the volume of the bay, so how fast the marsh is expanding or eroding can be predicted using geometry, knowing only the size of the basin, sea-level-rise rate, and the net rate of sediment import or export.
salt marsh; barrier island
Lauzon, Rebecca; Murray, A Brad; Moore, Laura J; Walters, David C.; Kirwan, Matthew L.; and Fagherazzi,, Sergio, Effects of Marsh Edge Erosion in Coupled Barrier Island-Marsh Systems and Geometric Constraints on Marsh Evolution (2018). JGR Earth Surface, 123(6), 1218-1234.