Salt Marsh Dynamics in a Period of Accelerated Sea Level Rise

Abstract

Salt marshes are dynamic systems able to laterally expand, contract, and vertically accrete in response to sea level rise. Here, we present the grand challenges that need to be addressed to fully characterize marsh morphodynamics. The review focuses on physical processes and quantitative models. Without predictive models, it is impossible to determine the future marsh evolution under accelerated sea level rise. In these models, one of the challenges is to resolve both horizontal and vertical dynamics within the same framework. Vertically, the marsh has to accumulate enough material to contrast rising water levels. Horizontally, marsh erosion at the ocean side must be compensated by landward expansion in forests, lawns, and agricultural fields. The dynamics of the marsh‐upland boundary are still not fully understood and will require more research in the upcoming years. The complexity of marsh vegetation is seldom captured in predictive models of marsh evolution. More research is needed to understand the effects of each species or species assemblages on hydrodynamics and sediment transport. Here, we further advocate that a sediment budget resolving all sediment fluxes in a marsh complex is the most important metric of marsh resilience. Characterization of these fluxes will enable to connect salt marshes to other landforms and to unravel feedbacks controlling the evolution of the entire coastal system. Current models of marsh evolution rely on sparse data sets collected at few locations. Novel remote sensing techniques will provide high‐resolution spatial data that will inform a new generation of computer models.

Coastal Wetland Resilience, Accelerated Sea‐Level Rise, and the Importance of Timescale

“…The advances outlined above offer new prospects for predicting the future trajectory and fate of global coastal wetlands. Complementing the recent contribution by Fagherazzi et al (2020), we highlight a few salient topics that are particularly relevant to maximize the potential of stratigraphic models of coastal wetland evolution. First of all, more paleo-records of coastal wetland change are needed to sample the rich variability of wetland response to RSLR that in all likelihood has not yet been fully captured.…”

Sediment Exchange Between the Created Saltmarshes of Living Shorelines and Adjacent Submersed Aquatic Vegetation in the Chesapeake Bay

“…However, the evolution of vertical and horizontal marshes over time is a topic that still requires future research. Vertically, marshes need to accumulate sediments to contrast SLR, while horizontally, they need landward expansion to compensate for erosion (Fagherazzi et al, 2020). The dynamics of marsh evolution will require future studies to provide us with tools to safeguard our coasts.…”

Seasonality and Characterization Mapping of Restored Tidal Marsh by NDVI Imageries Coupling UAVs and Multispectral Camera

“…Coastal regions are affected by a multitude of phenomena that significantly modify the dynamics of sediment transportation, such as storm surges, tidal processes and sea level rise [1][2][3][4]. Tidal wetland ecosystems, which are an integral part of many coastal systems, can also impact sediment dynamics, as well as promote biodiversity, enhance water quality, buffer coastal communities against sea level changes and storms, promote recreation and tourism and are recognized as an important blue carbon sink globally [5,6].…”

“…The combined effect of changing coastal hydrodynamics, sediment dynamics and ecological change (e.g., loss of submersed aquatic vegetation) within a coastal region could lead to increasing rates of erosion of the shoreline in certain areas. Therefore it is crucial to better understand the drivers of this process and to adopt efficient countermeasures for the successful restoration of the natural protection offered by well-vegetated systems along the coast [4,10]. Recent modeling efforts and field studies have been dedicated to better understanding the processes driving tidal marsh development [11].…”