Topological and Morphological Controls on Morphodynamics of Salt Marsh Interiors

Abstract

Salt marshes are important coastal environments and provide multiple benefits to society. They are considered to be declining in extent globally, including on the UK east coast. The dynamics and characteristics of interior parts of salt marsh systems are spatially variable and can fundamentally affect biotic distributions and the way in which the landscape delivers ecosystem services. It is therefore important to understand, and be able to predict, how these landscape configurations may evolve over time and where the greatest dynamism will occur. This study estimates morphodynamic changes in salt marsh areas for a regional domain over a multi-decadal timescale. We demonstrate at a landscape scale that relationships exist between the topology and morphology of a salt marsh and changes in its condition over time. We present an inherently scalable satellite-derived measure of change in marsh platform integrity that allows the monitoring of changes in marsh condition. We then demonstrate that easily derived geospatial and morphometric parameters can be used to determine the probability of marsh degradation. We draw comparisons with previous work conducted on the east coast of the USA, finding differences in marsh responses according to their position within the wider coastal system between the two regions, but relatively consistent in relation to the within-marsh situation. We describe the sub-pixel-scale marsh morphometry using a morphological segmentation algorithm applied to 25 cm-resolution maps of vegetated marsh surface. We also find strong relationships between morphometric indices and change in marsh platform integrity which allow for the inference of past dynamism but also suggest that current morphology may be predictive of future change. We thus provide insight into the factors governing marsh degradation that will assist the anticipation of adverse changes to the attributes and functions of these critical coastal environments and inform ongoing ecogeomorphic modelling developments.

Restoration and resilience to sea level rise of a salt marsh affected by dieback events in Charleston, SC

“…Linthurst and Seneca, 1980; Ogburn and Alber, 2006). The multiple stressors that lead to sudden vegetation dieback have yet to be completely revealed (Evans et al, 2021). The ability of unvegetated marshes to respond positively to grass planting is likely dependent on the strength of the marsh platform and whether it is located within the elevation range of a stable marsh domain (sensu Morris et al, 2002), along with sufficient sediment supply from the surrounding estuary USA which predicts an 88 % loss of initial marsh area by 2160 (Langston et al, 2021).…”

Salt‐marsh retreat on different time scales: Issues and prospects from a 5‐year monitoring campaign in the Venice Lagoon

“…vertical accretion and vegetation colonization) and those endangering it, such as surface and margin erosion. Rate of relative sea level rise (RSLR), tidal regime, wind‐wave climate, sediment supply, development of a vegetation cover related to RSLR, and temperature trend are fundamental driving forces for the morphologic evolution of salt marshes (Silvestri & Marani, 2004; Evans et al, 2019, 2021). Nowadays, shallow‐water environments are experiencing dramatic morphological and ecological degradation due to increasing anthropic pressure, RSLR, and erosive processes, intensified by a decrease in sediment supply (Fagherazzi et al, 2013; Mariotti & Fagherazzi, 2013).…”

Machine-Learning Classification of Soil Bulk Density in Salt Marsh Environments

“…Disturbances cause irreversible alterations in the condition of salt marsh communities over time [ 10 , 11 , 12 , 13 , 14 , 15 ]. Sea-level rise, drought, and physical alteration in soils, as well as changes in hydrological patterns, exert major pressures on salt marsh ecosystems [ 16 , 17 , 18 , 19 , 20 ]. Disturbances in salt marshes negatively impact soil structure, which is one of the main components of coastal wetlands and responsible for the high primary production of coastal marshes [ 21 , 22 , 23 , 24 ].…”