scholarly journals Unsupervised detection of salt marsh platforms: a topographic method

2017 ◽  
Author(s):  
Guillaume C. H. Goodwin ◽  
Simon M. Mudd ◽  
Fiona J. Clubb
Keyword(s):  
Salt Marsh ◽  
Salt Marshes ◽  
Tidal Flat ◽  
Near Infrared ◽  
Numerical Models ◽  
Storm Surges ◽  
Unsupervised Classification ◽  
Marsh Vegetation ◽  
Local Maxima ◽  
Topographic Evolution

Abstract. Salt marshes filter pollutants, protect coastlines against storm surges, and sequester carbon, yet are under threat from sea level rise and anthropogenic modification. The productivity and even survival of salt marsh vegetation depends on the topographic evolution of marsh platforms. Quantifying marsh platform topography is vital for improving the management of these valuable landscapes. Determining platform boundaries currently relies on supervised classification methods requiring near-infrared data to detect vegetation, or demands labor-intensive field surveys and digitization. We propose a novel, unsupervised method to reproducibly isolate saltmarsh scarps and platforms from a DEM, referred to as Topographic Identification of Platforms (TIP). Field observations and numerical models show that saltmarshes mature into sub-horizontal platforms delineated by sub-vertical scarps: based on this premise, we identify scarps as lines of local maxima on a slope raster, then fill landmasses from the scarps upward, thus isolating mature marsh platforms. We test the TIP method using lidar-derived DEMs from six saltmarshes in England with varying tidal ranges and geometries, for which topographic platforms were manually distinguished from tidal flats. Agreement between manual and unsupervised classification exceeds 94 % for DEM resolutions of 1 m, with all but one sites maintaining an accuracy superior to 90 % for resolutions up to 3 m. For resolutions of 1 m, platforms detected with the TIP method are comparable in surface area to digitized platforms, and have similar elevation distributions. We also find that our method allows the accurate detection of local bloc failures as small as 3 times the DEM resolution. Detailed inspection reveals that although tidal creeks were digitized as part of the marsh platform, unsupervised classification categorizes them as part of the tidal flat, causing an increase in false negatives and overall platform perimeter. This suggests our method would have increased accuracy if used in combination with existing creek detection algorithms. Fallen blocs and high tidal flat portions, associated with potential pioneer zones, may also be areas of discordance between our method and supervised mapping. Although pioneer zones prove difficult to classify using a topographic method, it also suggests that these transition areas should be considered when analysing erosion and accretion processes, particularly in the case of incipient marsh platforms. Ultimately, we have shown that unsupervised classification of marsh platforms from high-resolution topography is possible and sufficient to monitor and analyze topographic evolution.

scholarly journals Unsupervised detection of salt marsh platforms: a topographic method

2018 ◽  
Vol 6 (1) ◽  
pp. 239-255 ◽  
Author(s):  
Guillaume C. H. Goodwin ◽  
Simon M. Mudd ◽  
Fiona J. Clubb
Keyword(s):  
Salt Marsh ◽  
Salt Marshes ◽  
Tidal Flat ◽  
Near Infrared ◽  
Numerical Models ◽  
Storm Surges ◽  
Unsupervised Classification ◽  
Local Maxima ◽  
Elevation Model ◽  
Topographic Evolution

Abstract. Salt marshes filter pollutants, protect coastlines against storm surges, and sequester carbon, yet are under threat from sea level rise and anthropogenic modification. The sustained existence of the salt marsh ecosystem depends on the topographic evolution of marsh platforms. Quantifying marsh platform topography is vital for improving the management of these valuable landscapes. The determination of platform boundaries currently relies on supervised classification methods requiring near-infrared data to detect vegetation, or demands labour-intensive field surveys and digitisation. We propose a novel, unsupervised method to reproducibly isolate salt marsh scarps and platforms from a digital elevation model (DEM), referred to as Topographic Identification of Platforms (TIP). Field observations and numerical models show that salt marshes mature into subhorizontal platforms delineated by subvertical scarps. Based on this premise, we identify scarps as lines of local maxima on a slope raster, then fill landmasses from the scarps upward, thus isolating mature marsh platforms. We test the TIP method using lidar-derived DEMs from six salt marshes in England with varying tidal ranges and geometries, for which topographic platforms were manually isolated from tidal flats. Agreement between manual and unsupervised classification exceeds 94 % for DEM resolutions of 1 m, with all but one site maintaining an accuracy superior to 90 % for resolutions up to 3 m. For resolutions of 1 m, platforms detected with the TIP method are comparable in surface area to digitised platforms and have similar elevation distributions. We also find that our method allows for the accurate detection of local block failures as small as 3 times the DEM resolution. Detailed inspection reveals that although tidal creeks were digitised as part of the marsh platform, unsupervised classification categorises them as part of the tidal flat, causing an increase in false negatives and overall platform perimeter. This suggests our method may benefit from combination with existing creek detection algorithms. Fallen blocks and high tidal flat portions, associated with potential pioneer zones, can also lead to differences between our method and supervised mapping. Although pioneer zones prove difficult to classify using a topographic method, we suggest that these transition areas should be considered when analysing erosion and accretion processes, particularly in the case of incipient marsh platforms. Ultimately, we have shown that unsupervised classification of marsh platforms from high-resolution topography is possible and sufficient to monitor and analyse topographic evolution.

scholarly journals Multiscale Mapping of the Salt Marshes Using Sentinel-2, Dove and UAV Imagery in the Bay of Mont-Saint-Michel

2021 ◽  
Author(s):  
Antoine Collin ◽  
Dorothée James ◽  
Antoine Mury ◽  
Mathilde Letard ◽  
Thomas Houet ◽  
...  
Keyword(s):  
Salt Marsh ◽  
Salt Marshes ◽  
Vegetation Index ◽  
Near Infrared ◽  
Regional Scale ◽  
Great Promise ◽  
High Temporal Resolution ◽  
Multiscale Approach ◽  
Marsh Vegetation ◽  
Sentinel 2

The salt marshes, lying at the land-sea temperate interface, furnish a plethora of ecosystems services such as biodiversity niche support, ocean-climate change regulation, ornithology recreo-tourism or plant gathering by hand. They undergo significant worldwide losses due to their conversion into crop fields and to their spatial compression between the rising sea-level and the armoring shoreline. Their monitoring however requires to use a suite of remote sensing sensors to embrace the regional scale while capturing the plant details. This research innovatively adopts a multiscale approach using a cascading spaceborne and airborne process, from the 10-m Sentinel-2, through the 3-m Dove, to the 0.03-m unmanned airborne vehicle (UAV) imageries. The high to very high temporal resolution of the Sentinel-2 and Dove enabled to cover twenties and tens of km2 over five and four years, respectively, in the form of normalized difference vegetation index (NDVI) classes, associated with microphytobenthos, low, medium and high salt marsh vegetation, including the opportunistic Elyma genus. The NDVI was then modelled at the UAV scale (a few km2) using a three-layered NN prediction, providing the final near-infrared (NIR), and the intermediate red, green and blue reflectance imageries, calibrated/validated/tested with the Dove reflectance imageries (R2NIR=0.98, R2red=0.88, R2green=0.84, and R2blue=0.90). The 100fold increase in pixel size allowed to detect the decimeter-scale objects of the tidal flats and salt marshes, to enlarge the NDVI class ranges, and hold great promise to model other spectral bands at the UAV scale for further deeply enhancing the salt marsh mapping.

scholarly journals NATURE-BASED COASTAL PROTECTION: WAVE DAMPING BY FLEXIBLE SALT MARSH VEGETATION

2020 ◽  
pp. 9
Author(s):  
Thomas J van Veelen ◽  
Harshinie Karunarathna ◽  
William G Bennett ◽  
Tom P Fairchild ◽  
Dominic E Reeve
Keyword(s):  
Salt Marsh ◽  
Salt Marshes ◽  
Large Scale ◽  
Coastal Vegetation ◽  
Coastal Protection ◽  
Coastal Zones ◽  
Wave Damping ◽  
Marsh Vegetation ◽  
Efficient Manner ◽  
Wave Energy Dissipation

The ability of coastal vegetation to attenuate waves has been well established (Moller et al., 2014). Salt marshes are vegetated coastal wetlands that can act as nature- based coastal defenses. They exhibit a range of plant species, which have been shown to differ in the amount of wave damping they provide (Mullarney & Henderson, 2018). Recent studies have shown that plant flexibility is a key parameter that controls wave energy dissipation (Paul et al., 2016). Yet, no model exists that includes plant flexibility in computationally efficient manner for large-scale coastal zones. Therefore, we have developed a new model for flexible vegetation based on the key mechanisms in the wave-vegetation interaction and applied it to an estuary with diverse salt marsh vegetation.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/AjnFx3aFSzs

Coastal salt-marshes plant communities of the Salicornietea fruticosae class in Apulia (Italy)

Biologia ◽  
2014 ◽  
Vol 69 (1) ◽  
Author(s):  
Saverio Sciandrello ◽  
Valeria Tomaselli
Keyword(s):  
Salt Marsh ◽  
Plant Communities ◽  
Salt Marshes ◽  
Field Work ◽  
Salt Marsh Vegetation ◽  
Marsh Vegetation ◽  
Apulia Region ◽  
Coastal Salt Marshes ◽  
Ecological Features ◽  
Halocnemum Strobilaceum

AbstractAn overview of the salt-marsh herbland and scrub vegetation belonging to the class Salicornietea fruticosae Br.-Bl. et Tx. ex A. Bolòs y Vayreda 1950 in Apulia is presented. Data available from literature have been supplemented with original relevés performed in different locations of the Apulia region. On the basis of a total of 297 relevés, fifteen communities have been defined, according to the traditional phytosociological system based on dominant and/or diagnostic taxa. For comparison purposes, the salt-marsh vegetation has been classified using numerical methods. The results obtained show that most of the clusters correspond to specific associations, and confirm the division into vegetation alliances and orders. Numerical analysis also allowed us to assign the proper allocation of some associations and plant communities drawn from literature. Five alliances, with plant communities characterized by specific ecological features, have been discriminated: Sarcocornion alpini and Arthrocnemion glauci (lower marshes), Salicornion fruticosae (middle marshes), Inulion crithmoidis and Suaedion brevofoliae (upper marshes). In addition, during the field work, a population of Halocnemum strobilaceum (Arthrocnemo-Halocnemetum strobilacei), new record for the Apulia region, has been found.

scholarly journals Using Multispectral Drone Imagery for Spatially Explicit Modeling of Wave Attenuation through a Salt Marsh Meadow

Drones ◽  
2020 ◽  
Vol 4 (2) ◽  
pp. 25
Author(s):  
Antoine Mury ◽  
Antoine Collin ◽  
Thomas Houet ◽  
Emilien Alvarez-Vanhard ◽  
Dorothée James
Keyword(s):  
Salt Marsh ◽  
Salt Marshes ◽  
Crop Production ◽  
Vegetation Index ◽  
Near Infrared ◽  
Wave Attenuation ◽  
Coefficient Of Determination ◽  
Coastal Protection ◽  
Surface Model ◽  
Red Edge

Offering remarkable biodiversity, coastal salt marshes also provide a wide variety of ecosystem services: cultural services (leisure, tourist amenities), supply services (crop production, pastoralism) and regulation services including carbon sequestration and natural protection against coastal erosion and inundation. The consideration of this coastal protection ecosystem service takes part in a renewed vision of coastal risk management and especially marine flooding, with an emerging focus on “nature-based solutions.” Through this work, using remote-sensing methods, we propose a novel drone-based spatial modeling methodology of the salt marsh hydrodynamic attenuation at very high spatial resolution (VHSR). This indirect modeling is based on in situ measurements of significant wave heights (Hm0) that constitute the ground truth, as well as spectral and topographical predictors from VHSR multispectral drone imagery. By using simple and multiple linear regressions, we identify the contribution of predictors, taken individually, and jointly. The best individual drone-based predictor is the green waveband. Dealing with the addition of individual predictors to the red-green-blue (RGB) model, the highest gain is observed with the red edge waveband, followed by the near-infrared, then the digital surface model. The best full combination is the RGB enhanced by the red edge and the normalized difference vegetation index (coefficient of determination (R2): 0.85, root mean square error (RMSE): 0.20%/m).

Impact of salt marsh and seagrass beds on the sediemnt buget and resilience of coatsal areas

2020 ◽  
Author(s):  
Nicoletta Leonardi ◽  
Carmine Donatelli ◽  
Xiahoe Zhang ◽  
Neil Ganju ◽  
Sergio Fagherazzi
Keyword(s):  
Salt Marsh ◽  
Water Resources ◽  
Salt Marshes ◽  
Numerical Models ◽  
Sediment Budget ◽  
Coastal Protection ◽  
Seagrass Beds ◽  
Geophysical Research ◽  
Coastal System ◽  
Depositional Patterns

<p>Salt marshes and seagrass beds can offer sustainable coastal protection solutions and several ecosystem co-benefits. The delicate balance regulating salt marsh stability depends on several factors including the sediment added to and removed from the coastal system (<em>Donatelli et al., 2018, 2019; Zhang et al., 2019</em>).  Despite the importance of these sediment budget dynamics, many feedbacks between salt marsh presence and sediment availability are still unclear. Here, we use numerical models to simulate changes in depositional patterns of six estuaries along the U.S. coastline to investigate how salt marsh and seagrass beds removal and restoration can alter the sediment budget and resilience of coastal environments. </p><p><em>Donatelli, C., Ganju, N.K., Kalra, T.S., Fagherazzi, S. and Leonardi, N., 2019. Changes in hydrodynamics and wave energy as a result of seagrass decline along the shoreline of a microtidal back-barrier estuary. Advances in Water Resources, 128, pp.183-192.</em></p><p><em>Zhang, X., Leonardi, N., Donatelli, C. and Fagherazzi, S., 2019. Fate of cohesive sediments in a marsh-dominated estuary. Advances in water resources, 125, pp.32-40.</em></p><p><em>Donatelli, C., Ganju, N.K., Fagherazzi, S. and Leonardi, N., 2018. Seagrass impact on sediment exchange between tidal flats and salt marsh, and the sediment budget of shallow bays. Geophysical Research Letters, 45(10), pp.4933-4943.</em></p>

scholarly journals Changes in salt-marsh vegetation weakly affect top consumers of aquatic food webs

2020 ◽  
Author(s):  
Lafage Denis ◽  
Carpentier Alexandre ◽  
Sylvain Duhamel ◽  
Christine Dupuy ◽  
Eric Feunteun ◽  
...  
Keyword(s):  
Stable Isotopes ◽  
Salt Marsh ◽  
Salt Marshes ◽  
Vegetation Type ◽  
Site Effect ◽  
Salt Marsh Vegetation ◽  
Gut Content ◽  
Marsh Vegetation ◽  
Nitrogen Inputs

AbstractSalt marshes are under high, and increasing, anthropogenic pressures that have notably been reported to affect the diet of several fish species, probably resulting in nursery function alterations. Most of the previous studies in Europe were yet based on gut content analysis of fish, which can be considered a snapshot of immediate impacts of salt-marsh changes, and hardly of long-term effects of disturbances. In this study, we investigated the impact of vegetation type (resulting from both plant invasion and sheep grazing) by assessing trophic network (and especially fish diet and position) of different salt-marsh conditions. Replicated samples of basic sources (particular organic matter and microphytobenthos), dominant vegetation, potential aquatic and terrestrial prey and fish of 3 main species were taken during summer 2010 in two bays from Western France (Mont -Saint-Michel Bay and Seine Estuary) and analysed using C and N stable isotope compositions. All response variables tested (overall trophic organization, trophic niche and trophic position) provided consistent results, i.e. a dominant site effect and a weaker effect of vegetation type. Site effect was attributed to differences in anthropogenic Nitrogen inputs and tidal regime between the two bays, with more marine signatures associated with a higher frequency of flooding events. A second hypothesis is that E. acuta, which has recently totally replaced typical salt-marsh vegetation in Mont Saint-Michel Bay strongly impacted the nursery function. The trophic status of dominant fish species was unchanged by local salt-marsh vegetation, and considered consistent with their diet, i.e. high for predatory species (the sea bass Dicentrarchus labrax and the common goby Pomatoschistus microps) and lower for biofilm grazing species (the thinlip mullet Chelon ramada). This study finally highlights the relevance of stable isotopes analyses for assessing long-term and integrative effects of changes in vegetation resulting from human disturbances in salt marshes.HighlightsCross-ecosystem subsidies are of high functional importance, notably in salt marshesFish are vectors of exchanges, most European studies being based on their gut contentUsing stable isotopes we analysed the effect of surrounding vegetation on food websSurprisingly we found weak vegetation and strong site effects on all metricsNitrogen inputs, site accessibility and loss of nursery function can explain this factAbstract Figure

scholarly journals Long-term invasion dynamics of Spartina increase vegetation diversity and geomorphological resistance of salt marshes against sea level rise

2020 ◽  
Author(s):  
Dirk Granse ◽  
Sigrid Suchrow ◽  
Kai Jensen
Keyword(s):  
Salt Marsh ◽  
Species Diversity ◽  
Sea Level Rise ◽  
Sea Level ◽  
Salt Marshes ◽  
High Marsh ◽  
Marsh Vegetation ◽  
Vegetation Diversity ◽  
The Impact

AbstractThe cordgrass Spartina anglica C.E. Hubbard (Poaceae) is an invasive transformer in many salt marsh ecosystems worldwide. Relatively little is known about the capacity of Spartina to accelerate salt marsh succession and to protect salt marshes against sea level rise. We analyzed long-term changes in vegetation and elevation in mainland salt marshes of the European Wadden Sea in Schleswig-Holstein, Germany, to estimate the impact of non-native Spartina on the geomorphological resistance of salt marshes to sea level rise and on changes in species diversity. From 1989 to 2019, the Spartina-zone shifted and expanded upwards to elevations of the high marsh zone and Spartina increased in frequency in several salt marsh vegetation communities. At sites where Spartina dominated the vegetation already three decades ago, elevation and species diversity increased with a higher rate compared to sites lacking Spartina. The median change rates reached for elevation MHT +8.6 versus +1.5 mm per year, for species richness +3 versus $$\pm$$ ± 0 species per three decades, and for evenness +0.04 versus −0.08 per three decades, regarding plots with versus without former Spartina dominance, respectively. Invasion of salt marshes by Spartina and its continued, long-term presence were associated with increased elevation and species diversity in the face of sea level rise.

Salt marsh vegetation of the southern tundra subzone of Western Siberia: An example of the Baydaratskaya Bay coasts in the Kara Sea

2013 ◽  
Vol 3 (1) ◽  
pp. 58-68
Author(s):  
Luydmila M. Morozova ◽  
Svetlana N. Ektova
Keyword(s):  
Salt Marsh ◽  
Salt Marshes ◽  
Salt Water ◽  
Vascular Plant ◽  
Kara Sea ◽  
Coastal Vegetation ◽  
Salt Marsh Vegetation ◽  
Marsh Vegetation ◽  
Tidal Salt Marsh ◽  
Southern Tundra

The study is focused on the description of the vegetation and the general environment all characteristics of the salt marshes along coasts in the Baydaratskaya Bay there are of the Kara Sea in the southern tundra subzone of Russian Arctic. In tidal salt marsh habitats, several successional stages and types of communities depending on part of tidal zone. The plant communities study areas located close to research stations were represented by 50 species of vascular plant, 15 mosses and 3 lichens. The coastal vegetation tends to be floristically intermediate between the species composition of typical salt marshes communities (obligate and facultative halophytes) and species from adjacent tundra plains which can be able to tolerate occasional flooding by salt water. Zonation of salt marsh vegetation and floristic diversity were compared with the data for northern area of Kara Sea coasts.

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.

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