Potential of marshes to attenuate storm surge water level in the Chesapeake Bay

Glass, E. M., et al., 2018. Limnology and Oceanography

Original research (primary data)
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Abstract

Storm surges from tropical and extratropical storms frequently impact coastal communities globally. While the potential of natural and nature-based features for coastal defenses has gained increased attention as a viable option for coastal flood protection, the lack of in situ measurements of storm surge attenuation has delayed their widespread utilization. We present the findings of a 3-yr water level monitoring campaign that resulted in a large collection (52 flood events) of attenuation rates from marsh transects located in two natural preserves in the U.S. mid-Atlantic region. Results show that the overall marsh attenuated water levels, exhibiting values up to 0.02 cm/m at Eastern Shore of Virginia National Wildlife Refuge (ES) and 0.03 cm/m at Magothy Bay Natural Preserve (MGB). In general, the greatest attenuation rates were observed at the marsh edge section. The reach close to the coastline revealed an amplification of the water level followed by water level attenuation toward the backside of the marsh. However, analyses of five major storms at ES demonstrated that, within each event, the ability of the upper marsh to attenuate water level decreased with higher inundation heights. Additionally, small spatial scales of the marsh platform, geomorphological features such as channels, elevated surrounding forests and levees seem to play a major role in reducing the attenuation rates provided by the marshes. These results indicate that, while this type of marshland would provide storm surge attenuation during low inundation heights, these ecosystems would be less effective attenuating higher water depths from extreme events.

Case studies

Basic information

  • Case ID: INT-146-1
  • Intervention type: Protection
  • Intervention description:

    Natural reserve: the Eastern Shore of Virginia National Wildlife Refuge (hereafter ES) managed by the U.S. Fish and Wildlife Service

  • Landscape/sea scape ecosystem management: No
  • Climate change impacts Effect of Nbs on CCI Effect measures
    Storm surge  Mixed results overall attenuation rates (cm/m) - Positive and negative values represent water level attenuation and amplification respectively. attenuation rates during major storm events
  • Approach implemented in the field: Yes
  • Specific location:

    natural reserve site located in the U.S. mid-Atlantic region at the southern tip of the Delmarva Peninsula: the Eastern Shore of Virginia National Wildlife Refuge (hereafter ES)

  • Country: United States of America
  • Habitat/Biome type: Saltmarsh |
  • Issue specific term: Nature-based (general)

Evidence

  • Notes on intervention effectivness: effectiveness determined by looking at performance of the marsh over time and during storm events (no control) unclear for comparison to hybrid because although authors report outcomes for both, there is not a rigorous comparison (statistical or otherwise) performed mixed effectiveness: "These results indicate that this type of marshland would increase the attenuation during low inundation heights, but these ecosystems would be less effective attenuating high water depths." negative: "attenu- ation rates were significantly low or even negative (amplifi- cation) during the peak of the storms."
  • Is the assessment original?: Yes
  • Broadtype of intervention considered: Not applicable
  • Compare effectivness?: No
  • Compared to the non-NBS approach: Not applicable
  • Report greenhouse gas mitigation?: No
  • Impacts on GHG: Not applicable
  • Assess outcomes of the intervention on natural ecosystems: No
  • Impacts for the ecosystem: Not reported
  • Ecosystem measures:
  • Assess outcomes of the intervention on people: No
  • Impacts for people: Not reported
  • People measures:
  • Considers economic costs: No
  • Economic appraisal conducted: No
  • Economic appraisal described:
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  • Economic costs of alternative considered: No
  • Compared to an alternative: Not reported

Evaluation methodology

  • Type of data: Quantitative
  • Is it experimental: No
  • Experimental evalution done: Not applicable
  • Non-experimental evalution done: Empirical case study
  • Study is systematic:
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