Do salt marshes survive sea level rise? Modelling wave action, morphodynamics and vegetation dynamics

Best, Üwe S. N.; Wegen, Mick van der; Dijkstra, Jasper; Willemsen, Pim Wilhelmus Johannes Maria; Borsje, Bastiaan Wijnand; Roelvink, Dano

doi:10.1016/j.envsoft.2018.08.004

Cited by 92 publications

(89 citation statements)

References 49 publications

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“…They concluded from their global model simulations that area of global coastal wetlands could be increasing, provided they have sufficient accommodation space and sediment supply remains. Best et al (2018) [20] assessed saltmarsh-mudflat resilience to SLR and state that sediment deposition and biomass accumulation are determinants for saltmarsh survival. They concluded from their model analysis that these variables make saltmarshes resilient at first, but that they start to drown after 50-60 years.…”

Section: Introductionmentioning

confidence: 99%

Trends in the Seaward Extent of Saltmarshes across Europe from Long-Term Satellite Data

2019

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Saltmarshes provide crucial functions for flora, fauna, and humankind. Thus far, studies of their dynamics and response to environmental drivers are limited in space and time. Satellite data allow for looking at saltmarshes on a large scale and over a long time period. We developed an unsupervised decision tree classification method to classify satellite images into saltmarsh vegetation, mudflat and open water, integrating additional land cover information. By using consecutive stacks of three years, we considered trends while taking into account water level variations. We used Landsat 5 TM data but found that other satellite data can be used as well. Classification performance for different periods of the Western Scheldt was almost perfect for this site, with overall accuracies above 90% and Kappa coefficients of over 0.85. Sensitivity analysis characterizes the method as being robust. Generated time series for 125 sites across Europe show saltmarsh area changes between 1986 and 2010. The method also worked using a global approach for these sites. We reveal transitions between saltmarsh, mudflat and open water, both at the saltmarsh lower edge and interior, but our method cannot detect changes at the saltmarsh-upland boundary. Resulting trends in saltmarsh dynamics can be coupled to environmental drivers, such as sea level, tidal currents, waves, and sediment availability.

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Section: Introductionmentioning

confidence: 99%

Trends in the Seaward Extent of Saltmarshes across Europe from Long-Term Satellite Data

2019

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“…Others include detailed interactions between vegetation flow and inundation time but oversimplified vegetation‐induced sedimentation and erosion (e.g., Rodríguez et al, ). In long‐term modeling, growth and seasonality are usually simplified, where the salt marsh development is updated yearly or quarterly in, for example, Temmerman et al (), Rodríguez et al (), and Best et al (), or a factor is introduced accounting for reduced biomass in winter (Best et al, ; Mudd et al, ). Simplified bathymetries, hydrodynamics, and sediment transport computations limit the development of natural vegetation response in all these models, and the adaptation of the plants resilience with aging from seedling to mature life‐stages has not been accounted for in any ecomorphodynamic model so far.…”

Section: Introductionmentioning

confidence: 99%

Salt Marsh Establishment and Eco‐Engineering Effects in Dynamic Estuaries Determined by Species Growth and Mortality

et al. 2019

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Growth conditions and eco‐engineering effects of vegetation on local conditions in coastal environments have been extensively studied. However, interactions between salt marsh settling, growth, and mortality as a function of hydromorphology and eco‐engineering lack sufficient understanding to forecast morphological development of dynamic systems. We predict salt marsh establishment with an ecomorphodynamic model that accounts for literature‐based seasonal settling and life‐stage‐dependent growth and mortality of a generic salt marsh species. The model was coupled to a calibrated hydromorphodynamic model of an intertidal bar and, on a coarser grid, to the entire Western Scheldt estuary. To quantify the importance of eco‐engineering effects we compared the dynamic model results to a static model approach. The ecomorphodynamic model reproduces spatial pattern, cover, and growth trends over 15 years. The modeled vegetation cover emerges from the combination of a positive and a new negative eco‐engineering effect: vegetation reduces tidal flow strength facilitating plant survival while the developing salt marsh increases the hydroperiod, which limits large‐scale marsh expansion. The reproduced spatial gradient in vegetation density by our model is strongly correlated to their life‐stages, which underlines the importance of age‐dependence when modeling vegetation and for predictions of the stability of the marsh. Upscaling of the model to the entire estuary on a coarser grid gives implications for grid size‐dependent modeling of hydrodynamics and vegetation. In comparison with static model results, the eco‐engineering effects reduce vegetation cover, showing the importance of vegetation dynamics for predictions of salt marsh growth.

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“…SSC has declined in San Francisco Bay and estuary in recent decades, increasing the vulnerability of natural and restored marshes to sea-level rise (Schoellhamer, 2011). Modeling capabilities for assessing marsh resilience are developing rapidly (Fagherazzi et al, 2012;Best et al, 2018). However, there are few observational studies available for calibrating the complex biogeophysical interactions these models must simulate, particularly at wave-exposed In this paper we investigate sediment supply across the bay-marsh interface and its dependence on wave energy and season in a salt marsh in northern San Francisco Bay.…”

Section: Introductionmentioning

confidence: 99%

Seasonal Variation in Sediment Delivery Across the Bay‐Marsh Interface of an Estuarine Salt Marsh

et al. 2020

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Sediment transport across bay-marsh interfaces depends on wave energy, vegetation, and marsh-edge morphology and varies over a range of timescales. We investigated these dynamics in a tidal salt marsh with a gently sloped, vegetated edge adjacent to northern San Francisco Bay. Spartina foliosa (cordgrass) inhabits the lower marsh and Salicornia pacifica (pickleweed) predominates on the marsh plain. We measured suspended-sediment concentration (SSC) and hydrodynamics in bay shallows and along a 100-m cross-shore transect in the marsh, during winter and summer. Four-year averaged accretion measured with marker-horizon plots was twice as great along the marsh transect as adjacent to a tidal creek, 50 m from the bay. We estimated deposition and trapping efficiency from the time series data to assess its variation with season and wave energy. At high tide the transition zone (between cordgrass and pickleweed) was usually erosional, the pickleweed zone was depositional, and both erosion and deposition increased with wave energy, as did the landward position of maximum deposition. Erosion from the transition zone accounted for approximately one third of the sediment flux into the pickleweed. In the pickleweed zone, SSC, the difference between flood-and ebb-tide SSC, and trapping efficiency were greater in summer than winter for comparable wave conditions, which we attribute to increased sediment trapping by dense summer cordgrass. Moderate waves in summer (46%) accounted for more annual accretion in the pickleweed zone than larger waves in winter (28%), although the contribution of winter storms was diminished by the dry winter during the study.

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Do salt marshes survive sea level rise? Modelling wave action, morphodynamics and vegetation dynamics

Cited by 92 publications

References 49 publications

Trends in the Seaward Extent of Saltmarshes across Europe from Long-Term Satellite Data

Trends in the Seaward Extent of Saltmarshes across Europe from Long-Term Satellite Data

Salt Marsh Establishment and Eco‐Engineering Effects in Dynamic Estuaries Determined by Species Growth and Mortality

Seasonal Variation in Sediment Delivery Across the Bay‐Marsh Interface of an Estuarine Salt Marsh

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