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Abstract Sea level rise is leading to the rapid migration of marshes into coastal forests and other terrestrial ecosystems. Although complex biophysical interactions likely govern these ecosystem transitions, projections of sea level driven land conversion commonly rely on a simplified “threshold elevation” that represents the elevation of the marsh‐upland boundary based on tidal datums alone. To determine the influence of biophysical drivers on threshold elevations, and their implication for land conversion, we examined almost 100,000 high‐resolution marsh‐forest boundary elevation points, determined independently from tidal datums, alongside hydrologic, ecologic, and geomorphic data in the Chesapeake Bay, the largest estuary in the U.S. located along the mid‐Atlantic coast. We find five‐fold variations in threshold elevation across the entire estuary, driven not only by tidal range, but also salinity and slope. However, more than half of the variability is unexplained by these variables, which we attribute largely to uncaptured local factors including groundwater discharge, microtopography, and anthropogenic impacts. In the Chesapeake Bay, observed threshold elevations deviate from predicted elevations used to determine sea level driven land conversion by as much as the amount of projected regional sea level rise by 2050. These results suggest that local drivers strongly mediate coastal ecosystem transitions, and that predictions based on elevation and tidal datums alone may misrepresent future land conversion.
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Modeling the Impact of Hydraulic Reconnection on Estuary Hydrodynamics
Coastal environments around the globe are subject to anthropogenic stresses due to dense coastal populations. The response of development activities on dynamic estuarine ecosystems, influenced by tidal forces, freshwater flows, salinity variations, and intricate coastal land morphology, is often uncertain. This case study evaluates how connectivity and coastal geomorphology influence flow patterns by modeling the effects of a proposed hydraulic reconnection project on water movement between the Manchester Waterway, a coastal residential community, and Charlotte Harbor, a large open water estuary in the Gulf of Mexico. An unstructured grid, 2D model was developed utilizing Delft3D Flexible Mesh to simulate estuary hydrodynamics under proposed conditions for four different weather conditions, including recorded 2021–2022 weather, future sea level rise, an extreme weather event, and a combination of extreme weather and sea level rise. Simulated flow results for proposed conditions were compared to present day flow patterns for analysis of the predicted changes in water levels and velocity magnitudes in the waterway. The results show that increased connectivity between the Manchester Waterway and Charlotte Harbor is expected to increase tidal amplitudes largely due to a lowering of minimum water levels in the waterway. During storm events, water elevations are predicted to drop to lower elevations following peak storm surge due to proposed conditions, which may provide flooding relief. Model simulation results will aid hydraulic reconnection and guide a more comprehensive ecological restoration plan. This case study will also improve understanding of the major influencing forces in intricate estuarine environments and how ecosystems may respond to land development, sea level rise, and increasing magnitude and frequency of tropical storms.
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- Award ID(s):
- 1735320
- PAR ID:
- 10561252
- Publisher / Repository:
- American Ecological Engineering Society
- Date Published:
- Journal Name:
- Journal of Ecological Engineering Design
- ISSN:
- 2997-3112
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.21428/f69f093e.4f085bec
