Optimum vegetation height and density for inorganic sedimentation in deltaic marshes

Nardin, William; Edmonds, Douglas A.

doi:10.1038/ngeo2233

Cited by 135 publications

(141 citation statements)

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“…Such data can be highly useful in empirically testing hypothesized alternative stable states in coastal wetlands. To date, only a few studies have used remotely sensed data to try to quantitatively validate the presence of alternative stable states in coastal wetlands: Three studies in salt marshes [86,216], three in deltas [188,189,225], one in mangroves [264], and perhaps three in seagrasses [252,257,260], including the examples presented in Section 4. These studies are suggestive of the promise of using remotely sensed data to test alternative stable state hypotheses, but extensive and thorough testing for coastal environments and regular, accepted testing approaches and quantitative state metrics are so far lacking.…”

Section: Discussionmentioning

confidence: 99%

“…Remote sensing techniques have high potential for detecting, classifying, and mapping brackish, fresh, and deltaic marsh environments, which is reflected by the increasing number of papers on this topic (e.g., [188,189,224,225]). Remote sensing of coastal freshwater wetland spatial extent and land cover has often not accounted for the effects of changing water levels (e.g., [226]).…”

Section: Freshwater Tidal Wetlands and Deltasmentioning

confidence: 99%

“…Nardin and Edmonds [225] determined that intermediate vegetation heights best maximized sediment deposition in the freshwater marshes of the Wax Lake Delta, Louisiana (USA), that the impacts of vegetation on marsh sedimentation were seasonal and helped determine alternative stable states, and that a critical parameter for predicting vertical delta accretion was the relative timing of the seasonal flood wave and seasonal vegetation phenology.…”

Section: Freshwater Tidal Wetlands and Deltasmentioning

confidence: 99%

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Multiple Stable States and Catastrophic Shifts in Coastal Wetlands: Progress, Challenges, and Opportunities in Validating Theory Using Remote Sensing and Other Methods

et al. 2015

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Multiple stable states are established in coastal tidal wetlands (marshes, mangroves, deltas, seagrasses) by ecological, hydrological, and geomorphological feedbacks. Catastrophic shifts between states can be induced by gradual environmental change or by disturbance events. These feedbacks and outcomes are key to the sustainability and resilience of vegetated coastlines, especially as modulated by human activity, sea level rise, and climate change. Whereas multiple stable state theory has been invoked to model salt marsh responses to sediment supply and sea level change, there has been comparatively little empirical verification of the theory for salt marshes or other coastal wetlands. Especially lacking is long-term evidence documenting if or how stable states are established and maintained at ecosystem scales. Laboratory and field-plot studies are informative, but of necessarily limited spatial and temporal scope. For the purposes of long-term, coastal-scale monitoring, remote sensing is the best viable option. This review summarizes the above topics and highlights the emerging promise and challenges of using remote sensing-based analyses to validate coastal OPEN ACCESS Remote Sens. 2015, 7 10185 wetland dynamic state theories. This significant opportunity is further framed by a proposed list of scientific advances needed to more thoroughly develop the field.

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Section: Discussionmentioning

confidence: 99%

Section: Freshwater Tidal Wetlands and Deltasmentioning

confidence: 99%

Section: Freshwater Tidal Wetlands and Deltasmentioning

confidence: 99%

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Multiple Stable States and Catastrophic Shifts in Coastal Wetlands: Progress, Challenges, and Opportunities in Validating Theory Using Remote Sensing and Other Methods

et al. 2015

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“…Salt marshes are highly dynamic ecosystems, sequestrating on average 210 g CO 2 m -2 yr -1 through plant growth and decay (Chmura et al, 2003) and capturing additional inorganic sediment when they are submerged (Nardin and Edmonds, 2014). This productivity has allowed salt marshes to match historic sea level rise (Kirwan and Temmerman, 2009) and laterally expand when sediment inputs were sufficient (Kirwan et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Unsupervised detection of salt marsh platforms: a topographic method

Goodwin¹,

Mudd²,

Clubb³

2017

Preprint

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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 5 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 10England 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 15 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 20 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 possibleand sufficient to monitor and analyze topographic evolution.

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“…Hydrodynamic models are useful tools for exploring how climate change, rising sea levels, and hydrological regime alterations might affect the interaction between tides, rivers, and coastlines (Purvis et al, 2008;Bhuiyan and Dutta, 2012;Nardin and Edmonds, 2014), as well as urban coastal flooding (Gallien et al, 2013;Webster et al, 2014). Similarly, such models are vital in analysis of river hydrodynamics and floodplain inundation that might be affected by changing climate patterns (Wen et al, 2013;Vastila et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Representing hydrodynamically important blocking features in coastal or riverine lidar topography

Hodges

2015

Nat. Hazards Earth Syst. Sci.

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Abstract. New automated methods are developed for identifying narrow landscape features that cause hydrodynamic blocking and might have critical impacts for management models of river flooding, coastal inundation, climate change, or extreme event analysis. Lidar data processed into a fineresolution raster (1 m × 1 m) can resolve narrow blocking features in topography but typically cannot be directly used for hydrodynamic modeling. For practical applications such data are abstracted to larger scales, which can result in a loss of hydrodynamic blocking effects. The traditional approach to resolving hydrodynamic blocking features is to represent them as cell boundaries within a customized unstructured grid that is tuned to the spatial features. A new automated edge-blocking approach is developed, which allows application of an arbitrarily structured (Cartesian) mesh at coarser scales and provides contiguous representation of blocking features along Cartesian cell boundaries. This approach distorts the shape of a blocking feature (i.e., making it rectilinear along grid cell faces) but retains its critical hydrodynamic blocking height characteristics and spatial continuity within the topographic model.

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Optimum vegetation height and density for inorganic sedimentation in deltaic marshes

Cited by 135 publications

References 27 publications

Multiple Stable States and Catastrophic Shifts in Coastal Wetlands: Progress, Challenges, and Opportunities in Validating Theory Using Remote Sensing and Other Methods

Multiple Stable States and Catastrophic Shifts in Coastal Wetlands: Progress, Challenges, and Opportunities in Validating Theory Using Remote Sensing and Other Methods

Unsupervised detection of salt marsh platforms: a topographic method

Representing hydrodynamically important blocking features in coastal or riverine lidar topography

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