TY - JOUR
T1 - Modeling Decadal Salt Marsh Development
T2 - Variability of the Salt Marsh Edge Under Influence of Waves and Sediment Availability
AU - Willemsen, P. W.J.M.
AU - Smits, B. P.
AU - Borsje, B. W.
AU - Herman, P. M.J.
AU - Dijkstra, J. T.
AU - Bouma, T. J.
AU - Hulscher, S. J.M.H.
PY - 2022
Y1 - 2022
N2 - Salt marshes can contribute to coastal protection, but the magnitude of the protection depends on the width of the marsh. The cross-shore width of the marsh is to a large extent determined by the delicate balance between seaward expansion and landward retreat. The influence of the magnitude of daily occurring mild weather conditions and sediment availability on the variability of salt marsh width has not been systematically assessed. This paper investigates how the magnitude of homogeneous hydrodynamic forcing, combined with sediment availability, affects the biophysical development, and more specifically retreat and expansion of salt marshes. The dynamic extent of the salt marsh is assessed by modeling online-coupled hydrodynamics, morphodynamics and vegetation growth using the numerical Delft3D-Flexible Mesh model, and a vegetation growth module. Simulated patterns around the salt marsh edge resembled field observations, as well as the simulated temporal variability of the lateral position of the salt marsh edge. In the model, the salt marsh extended seaward at low wave forcing (0.00 m; 0.05 m), and retreated landward at higher wave forcing (0.10 m; 0.15 m). With increasing physical stress, the salt marsh edge was found at lower elevations, indicating an unhealthy system with a retreating marsh edge due to vegetation mortality, whereas decreasing physical stresses result in a higher salt marsh edge, enabling expansion. This balance suggests the importance of response time of vegetation to physical stress. Yet, the salt marsh forced with higher waves was able to switch from a retreating extent retrogradational to an expansional behavior as sediment supply increased.
AB - Salt marshes can contribute to coastal protection, but the magnitude of the protection depends on the width of the marsh. The cross-shore width of the marsh is to a large extent determined by the delicate balance between seaward expansion and landward retreat. The influence of the magnitude of daily occurring mild weather conditions and sediment availability on the variability of salt marsh width has not been systematically assessed. This paper investigates how the magnitude of homogeneous hydrodynamic forcing, combined with sediment availability, affects the biophysical development, and more specifically retreat and expansion of salt marshes. The dynamic extent of the salt marsh is assessed by modeling online-coupled hydrodynamics, morphodynamics and vegetation growth using the numerical Delft3D-Flexible Mesh model, and a vegetation growth module. Simulated patterns around the salt marsh edge resembled field observations, as well as the simulated temporal variability of the lateral position of the salt marsh edge. In the model, the salt marsh extended seaward at low wave forcing (0.00 m; 0.05 m), and retreated landward at higher wave forcing (0.10 m; 0.15 m). With increasing physical stress, the salt marsh edge was found at lower elevations, indicating an unhealthy system with a retreating marsh edge due to vegetation mortality, whereas decreasing physical stresses result in a higher salt marsh edge, enabling expansion. This balance suggests the importance of response time of vegetation to physical stress. Yet, the salt marsh forced with higher waves was able to switch from a retreating extent retrogradational to an expansional behavior as sediment supply increased.
KW - biogeomorphological dynamics
KW - building with nature
KW - Delft3D-FM
KW - nature based flood defense
KW - salt marsh
KW - vegetation development
UR - http://www.scopus.com/inward/record.url?scp=85123606337&partnerID=8YFLogxK
U2 - 10.1029/2020WR028962
DO - 10.1029/2020WR028962
M3 - Article
AN - SCOPUS:85123606337
SN - 0043-1397
VL - 58
JO - Water Resources Research
JF - Water Resources Research
IS - 1
M1 - e2020WR028962
ER -