Understanding and predicting changes in coastal marsh ecosystemsservices: realizing the combined effects of sea-level rise, tides, and storm surge on marshes and their capacity to protect shorelines.

Research project

Description

Rising sea levels and exposure to increasingly energetic storms are the two aspects of global climate change that most seriously challenge the resilience of coastal ecosystems and human communities. Preventing the loss of ecosystem services provided by coastal marsh habitat represents a crucial challenge to the coastal environment. Flooding risk and attendant damages to natural resources on our estuarine shores depend upon local sea levels along with storm surge, tidal phase and/or meteorological state, and wave conditions. First, this project will model the joint influence of local sea-level rise (low, medium, and high scenarios), storm surge, local wind waves, and tidal stage on water levels at chosen estuarine shoreline locations using ADCIRC Lite. These predictions will be tested using 8 years of as yet unpublished continuous water-level data at two marsh shores within the North Carolina (NC) Sentinel Site Cooperative (SSC), one on Bogue Sound with astronomical tidal forcing dominant and the other on southern Pamlico Sound with meteorological forcing dominant. By decomposing the tidal harmonics and identifying the meteorological influence in those records, for each site this project will examine the importance of different forcing variables. This project will isolate water level data for each hurricane and tropical storm (5 impacted NC in those 8 years) and the 5 most energetic northeasters and use these records to test the predictions of the ADCIRC Lite model. Second, this project will develop a new marsh wave attenuation model from basic physical principles and field measurements at 10 sites within the NC SSC boundary. Marshes at these sites are composed of two structurally different alternative dominant marsh macrophytes, Spartina alterniflora and Juncus roemerianus which are expected to have different wave attenuation properties. Opportunistic storm sampling at selected sites will test predictions of the model. Using this model, we will examine marsh wave attenuation capacity at the 10 sites under present day conditions and future scenarios. For each scenario, we will examine how wave attenuation capacity varies across a range of realistic storm surge and incident wind wave conditions determined from statistical distributions developed for FEMA and modeled by ADCIRC Lite. Simulations will be repeated for different sea-level rise and storm scenarios at each time period. For each site, the marsh position, extent, and plant community will be adjusted for sea-level rise using a digital elevation model. Field measurements of site topography and plant distribution will be used to predict the extent and condition of marsh habitat over 1-50 years, recognizing limitations to landward transgression based on barriers including steep slopes. Wave attenuation capacity will then be computed for these new marsh distributions across the range of expected storm surge and wave conditions. Marsh habitat changes will also be translated into changes in the delivery of other macrophyte-related ecosystem services: trophic contribution and hydrologic processing. By comparing the resilience and ecosystem service capacities of the two marsh dominants, managers can target the best species or mixed species pattern for restoration projects, remove identified barriers to up-slope transgression, and provide guidance to coastal property owners on the value of marsh habitat in protecting their shoreline properties. Finally, the King Tides Project will be implemented in NC with other outreach efforts to increase public awareness about coastal inundation issues and the value of natural assets.
StatusActive
Effective start/end date9/1/158/31/18

Funding

  • NOAA NOS National Centers for Coastal Ocean Science (NCCOS)

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storm surge
marsh
shoreline
tide
sea level rise
effect
project
wave attenuation
habitat
ecosystem service
water level
prediction
wind wave
transgression
energetics
statistical distribution
macrophyte
hurricane
digital elevation model
coastal zone