Modelling decadal salt marsh development: variability of the salt marsh edge under influence of waves and sediment availability

2021 ◽  
Author(s):  
P. W. J. M. Willemsen ◽  
B. P. Smits ◽  
B. W. Borsje ◽  
P. M. J. Herman ◽  
J. T. Dijkstra ◽  
...  
Keyword(s):  
Salt Marsh ◽  
Marsh Edge

scholarly journals Near-Continuous Monitoring of a Coastal Salt Marsh Margin: Implications to Predicting Marsh Edge Erosion

2020 ◽  
Author(s):  
Jack A. Cadigan ◽  
Navid Jafari ◽  
Nan Wang ◽  
Qin Jim Chen ◽  
Ling Zhu ◽  
...  
Keyword(s):  
Salt Marsh ◽  
Continuous Monitoring ◽  
Marsh Edge ◽  
Coastal Salt Marsh

scholarly journals Detecting the Morphology of Prograding and Retreating Marsh Margins—Example of a Mega-Tidal Bay

2019 ◽  
Vol 12 (1) ◽  
pp. 13
Author(s):  
Guillaume Goodwin ◽  
Simon Mudd
Keyword(s):  
Salt Marsh ◽  
Lidar Data ◽  
Lateral Motion ◽  
Vertical Accretion ◽  
Marsh Edge ◽  
The Future ◽  
Change Event ◽  
Event Magnitude ◽  
Do So

Retreat and progradation make the edges of salt marsh platforms their most active features. If we have a single topographic snapshot of a marsh, is it possible to tell if some areas have retreated or prograded recently or if they are likely to do so in the future? We explore these questions by characterising marsh edge topography in mega-tidal Moricambe Bay (UK) in 2009, 2013 and 2017. We first map outlines of marsh platform edges based on lidar data and from these we generate transverse topographic profiles of the marsh edge 10 m long and 20 m apart. By associating profiles with individual retreat or progradation events, we find that they produce distinct profiles when grouped by change event, regardless of event magnitude. Progradation profiles have a shallow scarp and low relief that decreases with event magnitude, facilitating more progradation. Conversely, steep-scarped, high-relief retreat profiles dip landward as retreat reveals older platforms. Furthermore, vertical accretion of the marsh edge is controlled by elevation rather than its lateral motion, suggesting an even distribution of deposition that would allow bay infilling were it not limited by the migration of creeks. While we demonstrate that marsh edges can be quantified with currently available DTMs, oblique observations are crucial to fully describe scarps and better inform their sensitivity to wave and current erosion.

scholarly journals Salt marsh stabilization affects algal primary producers at the marsh edge

2011 ◽  
Vol 19 (2) ◽  
pp. 131-140 ◽  
Author(s):  
Mary I. O’Connor ◽  
Christy R. Violin ◽  
Andrea Anton ◽  
Laura M. Ladwig ◽  
Michael F. Piehler
Keyword(s):  
Salt Marsh ◽  
Primary Producers ◽  
Marsh Edge

The influence of grain size and frictional/cohesional shear strength components on UK salt marsh substrate stability

2020 ◽  
Author(s):  
Helen Brooks ◽  
Iris Moeller ◽  
Tom Spencer ◽  
Kate Royse
Keyword(s):  
Shear Strength ◽  
Salt Marsh ◽  
Internal Friction ◽  
Water Levels ◽  
Systematic Research ◽  
Surface Erosion ◽  
Marsh Edge ◽  
Angle Of Internal Friction ◽  
Erosion Processes ◽  
Ring Shear

<p>Salt marshes attenuate waves and currents, thus protecting landward-lying constructed defences and the hinterland from incoming waves and extreme water levels. As such, understanding the stability of the marsh sedimentary platform is important, particularly as marsh edge erosion is common on many shores. To understand why marshes are losing material from their exposed fringes, we must better understand the relations between the marsh fabric and incoming hydrodynamic energy; this is likely to be strongly influenced by marsh biological, geochemical and sedimentological/geotechnical properties. Currently there is little systematic research into the within- and between-marsh variability in these properties and how they affect both marsh edge and marsh surface erosion processes.</p><p> </p><p>We compare Tillingham marsh, eastern England, where the sediment is clay/silt-dominated and the marsh canopy is species-rich, to Warton marsh, Morecambe Bay, NW England, where the sediment is sand/silt-dominated and the vegetation species-poor. We determine soil shear strength by applying geotechnical methods which, to the best of our knowledge, have not previously been applied to salt marsh environments. Shear box and ring shear tests are used to determine the natural- and residual (i.e. post-failure) shear strength of the substrate, respectively. This is expressed as the cohesion of the sediment and the angle of internal friction. We demonstrate that the ring shear test consistently returns a lower angle of internal friction for the substrate, which is expected for the residual angle of internal friction. However, we are also able to link this reduction in the angle of internal friction to substrate composition (e.g. root content, organic matter and particle size distribution). This enhanced methodological understanding will improve our comprehension of marsh resistance to edge erosion and thus our ability to predict future erosion. Ultimately, accurate measurements of the shear strength of natural foreshores are essential for the informed implementation of nature-based coastal flood defences, including ‘de-embankment’/‘managed realignment’ schemes.</p>

scholarly journals GEOTECHNICAL PROPERTIES OF SALT MARSH AND TIDAL FLAT SUBSTRATES AT TILLINGHAM, ESSEX, UK.

2018 ◽  
pp. 55
Author(s):  
Helen Brooks ◽  
Iris Möller ◽  
Tom Spencer ◽  
Kate Royse ◽  
Simon James Price
Keyword(s):  
Salt Marsh ◽  
Systematic Study ◽  
Salt Marshes ◽  
Tidal Flat ◽  
Marsh Surface ◽  
Geotechnical Properties ◽  
Surface Erosion ◽  
Marsh Edge ◽  
Erosion Risk ◽  
Erosion Processes

Salt marshes and, to a lesser extent, tidal flats, attenuate incoming hydrodynamic energy, thus reducing flood and erosion risk in the coastal hinterland. However, marshes are declining both globally and regionally (the Northwest European region). Salt marsh resistance to incoming hydrodynamic forcing depends on marsh biological, geochemical and geotechnical properties. However, there currently exists no systematic study of marsh geotechnical properties and how these may impact both marsh edge and marsh surface erosion processes (e.g. surface removal, cliff undercutting, gravitational slumping). This has led to poor parameterization of marsh evolution models. Here, we present a systematic study of salt marsh and tidal flat geotechnical properties (shear strength, bulk density, compressibility, plasticity and particle size) at Tillingham, Essex, UK.

scholarly journals Identifying Salt Marsh Shorelines from Remotely Sensed Elevation Data and Imagery

2019 ◽  
Vol 11 (15) ◽  
pp. 1795 ◽  
Author(s):  
Amy S. Farris ◽  
Zafer Defne ◽  
Neil K. Ganju
Keyword(s):  
Salt Marsh ◽  
High Resolution ◽  
Salt Marshes ◽  
Spatial Scales ◽  
Remotely Sensed ◽  
Horizontal Resolution ◽  
Unmanned Aircraft ◽  
Maximum Slope ◽  
Marsh Edge ◽  
Elevation Data

Salt marshes are valuable ecosystems that are vulnerable to lateral erosion, submergence, and internal disintegration due to sea level rise, storms, and sediment deficits. Because many salt marshes are losing area in response to these factors, it is important to monitor their lateral extent at high resolution over multiple timescales. In this study we describe two methods to calculate the location of the salt marsh shoreline. The marsh edge from elevation data (MEED) method uses remotely sensed elevation data to calculate an objective proxy for the shoreline of a salt marsh. This proxy is the abrupt change in elevation that usually characterizes the seaward edge of a salt marsh, designated the “marsh scarp.” It is detected as the maximum slope along a cross-shore transect between mean high water and mean tide level. The method was tested using lidar topobathymetric and photogrammetric elevation data from Massachusetts, USA. The other method to calculate the salt marsh shoreline is the marsh edge by image processing (MEIP) method which finds the unvegetated/vegetated line. This method applies image classification techniques to multispectral imagery and elevation datasets for edge detection. The method was tested using aerial imagery and coastal elevation data from the Plum Island Estuary in Massachusetts, USA. Both methods calculate a line that closely follows the edge of vegetation seen in imagery. The two methods were compared to each other using high resolution unmanned aircraft systems (UAS) data, and to a heads-up digitized shoreline. The root-mean-square deviation was 0.6 meters between the two methods, and less than 0.43 meters from the digitized shoreline. The MEIP method was also applied to a lower resolution dataset to investigate the effect of horizontal resolution on the results. Both methods provide an accurate, efficient, and objective way to track salt marsh shorelines with spatially intensive data over large spatial scales, which is necessary to evaluate geomorphic change and wetland vulnerability.

scholarly journals Estimating and Applying Fish and Invertebrate Density and Production Enhancement from Seagrass, Salt Marsh Edge, and Oyster Reef Nursery Habitats in the Gulf of Mexico

2021 ◽  
Author(s):  
Philine S. E. zu Ermgassen ◽  
Bryan DeAngelis ◽  
Jonathan R. Gair ◽  
Sophus zu Ermgassen ◽  
Ronald Baker ◽  
...  
Keyword(s):  
Salt Marsh ◽  
Gulf Of Mexico ◽  
Salt Marshes ◽  
Fish Habitat ◽  
Juvenile Fish ◽  
Oyster Reefs ◽  
Coastal Habitats ◽  
Marsh Edge ◽  
Northern Gulf Of Mexico ◽  
Nursery Habitats

AbstractSeagrasses, oyster reefs, and salt marshes are critical coastal habitats that support high densities of juvenile fish and invertebrates. Yet which species are enhanced through these nursery habitats, and to what degree, remains largely unquantified. Densities of young-of-year fish and invertebrates in seagrasses, oyster reefs, and salt marsh edges as well as in paired adjacent unstructured habitats of the northern Gulf of Mexico were compiled. Species consistently found at higher densities in the structured habitats were identified, and species-specific growth and mortality models were applied to derive production enhancement estimates arising from this enhanced density. Enhancement levels for fish and invertebrate production were similar for seagrass (1370 [SD 317] g m–2 y–1for 25 enhanced species) and salt marsh edge habitats (1222 [SD 190] g m–2 y–1, 25 spp.), whereas oyster reefs produced ~650 [SD 114] g m–2 y–1(20 spp). This difference was partly due to lower densities of juvenile blue crab (Callinectes sapidus) on oyster reefs, although only oyster reefs enhanced commercially valuable stone crabs (Menippe spp.). The production estimates were applied to Galveston Bay, Texas, and Pensacola Bay, Florida, for species known to recruit consistently in those embayments. These case studies illustrated variability in production enhancement by coastal habitats within the northern Gulf of Mexico. Quantitative estimates of production enhancement within specific embayments can be used to quantify the role of essential fish habitat, inform management decisions, and communicate the value of habitat protection and restoration.

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