Complexity in salt marsh circulation for a semienclosed basin

Sullivan, J. C.; Torres, Raymond; Garrett, Alfred J.; Blanton, Jackson O.; Alexander, Clark; Robinson, Michael; Moore, Trent; Amft, J.; Hayes, D.W.

doi:10.1002/2014jf003365

Cited by 24 publications

(32 citation statements)

References 48 publications

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“…Another important aspect to consider is the Manning's roughness coefficient (n) associated with land cover classes in the model domain. We use updated emergent herbaceous wetland regions to assign n-coefficient values of subtidal channels (n = 0.017) and salt marsh platforms (n = 0.10) of Savannah similar to those reported in Sullivan et al (2015). The remaining n-coefficient values of the 2016 NLCD are initially derived from Liu et al (2018) and further calibrated as described in the next section.…”

Section: Wetland Elevation Correctionmentioning

confidence: 99%

Compound Effects of Flood Drivers and Wetland Elevation Correction on Coastal Flood Hazard Assessment

Muñoz

Moftakhari

Moradkhani

2020

Water Resources Research

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Compound flooding frequently threatens life and assets of people who live in low‐lying coastal regions. Co‐occurrence or sequence of extremes (e.g., high river discharge and extreme coastal water level) is of paramount importance as it may result in flood hazards with potential impacts larger than each extreme in isolation. Here, we use a coupled approach, that is, bivariate statistical analysis linked to hydrodynamic modeling, to quantify compounding effects of flood drivers and generate flood hazard maps near Savannah, Georgia. Also, we integrate wetland elevation correction in digital elevation models to improve hydrodynamic simulations of compound events and hence the accuracy of flood hazard (inundation and velocity) maps. Using statistical measures, we analyze compounding effects of terrestrial/coastal flood drivers and wetland elevation correction on maximum floodwater height (MFH) and velocity (MFV) for 50‐year return period scenarios. In addition, we compare our results to MFH and MFV patterns of Hurricane Matthew that hit the West Atlantic Coasts on October 2016. The statistical measures indicate significant differences among the scenarios, partly explained by wetland elevation correction. Inundation and velocity maps suggest that a proposed composite, that is, synthesis of marginal Q, marginal H, and “AND” scenarios, can lead to the lowest average underestimation of MFH (−0.35 m) and overestimation of MFV (0.20 m/s) within wetland areas. We conclude that a thorough compound flooding assessment should leverage statistical analysis and hydrodynamic modeling of extremes including corrections of coastal digital elevation models.

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Section: Wetland Elevation Correctionmentioning

confidence: 99%

Compound Effects of Flood Drivers and Wetland Elevation Correction on Coastal Flood Hazard Assessment

Muñoz

Moftakhari

Moradkhani

2020

Water Resources Research

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“…(1) and t is the length of time that a particle of water stays in the system, and a and b are dispersion coefficients that influence the time variation of the random spreading process and emerge from model calibration (Bent et al, 1991). For these 2-D flow simulations, a roughness length parameter of 0.001 m was specified (Nepf & Ghisalberti, 2008;Raupach, 1994;Sullivan et al, 2015), and this in turn helped determine the logarithmic vertical velocity profile.…”

Section: Model Description and Setupmentioning

confidence: 99%

“…In other words, Blanton et al () implied that first‐order creek systems facilitate greater overall salt marsh circulation. Later, the same site was surveyed in high detail using a real‐time kinematic global positioning system, and Sullivan et al () used the resulting DEM in simulations of overmarsh flow. They showed highly complex flow patterns in both space and time, and they associated this response with the submergence/emergence of decimeter‐scale topography.…”

Section: Introductionmentioning

confidence: 99%

Intertidal Creeks and Overmarsh Circulation in a Small Salt Marsh Basin

2019

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The role of intertidal creek networks in overmarsh circulation is not well constrained. In this study, we systematically remove intertidal creeks from a high‐resolution salt marsh digital elevation model and conduct new flow simulations with each iteration. Overall, removal of first‐ and second‐order creeks reduced drainage density by 65%, and this had a negligible effect on overmarsh circulation and tracer distribution. However, upon removal of third‐ and fourth‐order creeks, drainage density was reduced by 80% of the original value, and changes in peak velocity magnitude across various spatial and temporal scales reveal a system‐wide switch from ebb to flood dominance. This response coincides with the interruption of topographically connected creeks that facilitate the direct exchange of water and tracer between the marsh interior and the larger subtidal system. Further, this reduction in hydraulic connectivity gives rise to less expansive tracer dispersal and a systematic decline in tracer residence time. Together, these results reveal that for the Groves Creek marsh, lower‐order intertidal creeks have a minor role in overmarsh circulation, while higher‐order creeks increase the potential for short circuiting of flow; they greatly influence overall flood and ebb dominance, and net tracer dispersal and associated retention time. Results reported here provide new insight on, for example, salt marsh restoration and the requisite digital elevation model bathymetry for robust simulations of overmarsh circulation.

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“…; Sullivan et al. ). However, it is extremely time consuming to simulate a real‐world salt marsh system with such a small grid size and a small time step.…”

Section: Introductionmentioning

confidence: 99%

“…A literature review of Manning coefficients revealed a large range of values between 0.006 and 0.63 s m −1/3 (Sullivan et al. ). Such a wide range of bottom roughness values makes it difficult to calibrate models.…”

Section: Introductionmentioning

confidence: 99%

Subgrid modeling of salt marsh hydrodynamics with effects of vegetation and vegetation zonation

Liang

et al. 2017

Earth Surf Processes Landf

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Vegetation plays a critical role in modifying inundation and flow patterns in salt marshes. In this study, the effects of vegetation are derived and implemented in a high-resolution, subgrid model recently developed for simulating salt marsh hydrodynamics. Vegetation-induced drag forces are taken into account as momentum sink terms. The model is then applied to simulate the flooding and draining processes in a meso-tidal salt marsh, both with and without vegetation effects. Marsh inundation and flow patterns are significantly changed with the presence of vegetation. A smaller area of inundation occurs when vegetation is considered. Tides propagate both on the platform and through the channels when vegetation is absent, whereas flows concentrate mainly in channels when vegetation is present. Local inundation on vegetated platforms is caused mainly by water flux spilled from nearby channels, with a flow direction perpendicular to the channel edges, whereas inundation on bare platforms has contributions from both local spilled-over water flux and remote advection from adjacent platforms. The flooding characteristics predicted by the model showed a significant difference between higher marsh and lower marsh, which is consistent with the wetlands classification by the National Wetlands Inventory (NWI). The flooding characteristics and spatial distribution of hydroperiod are also highly correlated with the vegetation zonation patterns observed in Google Earth imagery. Regarding the strong interaction between flow, vegetation and geomorphology, the conclusion highlights the importance of including vegetation in the modeling of salt marsh dynamics.

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Complexity in salt marsh circulation for a semienclosed basin

Cited by 24 publications

References 48 publications

Compound Effects of Flood Drivers and Wetland Elevation Correction on Coastal Flood Hazard Assessment

Compound Effects of Flood Drivers and Wetland Elevation Correction on Coastal Flood Hazard Assessment

Intertidal Creeks and Overmarsh Circulation in a Small Salt Marsh Basin

Subgrid modeling of salt marsh hydrodynamics with effects of vegetation and vegetation zonation

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