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The impact of accelerated sea level rise
on coastal wetlands and its implications
on storm surge
- The story of lower Pascagoula River Basin in
Jackson County, MS
Wei Wu1, Maria Kalcic2, Jason Fleming3
March 6, 2012
1. The University of Southern Mississippi
2. Computer Science Corp
3. Seahorse Coastal Consulting
GHGs are changing, but growing at a
unprecedented accelerated rate
Atmospheric concentrations of CO2, CH4
and N2O over the last 10,000 years (large
panels) and since 1750 (inset panels).
Measurements are shown from ice cores
and atmospheric samples (red lines). The
corresponding radiative forcing relative to
1750 are shown on the right hand axes of
the large panels.
From IPCC Climate Change 2007: Synthesis report
Surface temperature, seal level and snow cover are
changing, but at a unprecedented accelerated rate
Observed changes in
a) Global average surface
temperature;
b) Global average sea level
from tide gauge (blue) and
satellite (red);
c) Northern hemisphere snow
cover for March-April.
Smoothed curves represent
decadal averaged values
while circles show yearly
values. The shaded areas
are the uncertainty intervals.
From IPCC Climate Change 2007: Synthesis report
Consequences of climate change
•
•
Alter ecosystem services and affect the ability of
biological systems to support human needs
(Vitousek et al. 1997)
e.g. degradation in water quality, productivity and
extractable resources;
Interact with other environmental stressors:
elevated acidic atmospheric deposition,
accelerated sea level rise, hurricanes etc.
Coastal wetland
• Coastal wetlands are ecologically, economically and
socially important to humans as they provide the
benefits of storm protection, flood control, habitat for
commercially important fisheries and wildlife, improved
water quality through sediment, nutrient and pollutant
removal, recreation, and aesthetic value.
• In particular, coastal wetlands can reduce storm surge
potential by acting as a physical barrier and creating
frictional resistance for the surge and waves. They may
also reduce surge potential and flooding risks by reducing
surface winds due to higher sub-aerial surface roughness
and by slowing surge propagation due to bottom friction
in shallow flow at the inundation front.
Objectives
• Simulate the impact of different sea level rise scenarios
on coastal wetland;
• How the area and location changes of coastal wetland
affect storm surge predictions
• Simulate the impact of SLR on coastal wetland
Method
• Sea Level Affecting Marshes Model (SLAMM 6.0.1 beta)
Simulates the dominant processes involved in wetland conversions and
shoreline modifications during long-term sea-level rise : Inundation,
Erosion, Overwash, Saturation, Accretion, Salinity
• SLAMM integrates elevation–submergence and wave action–
erosion. SLAMM also incorporates a salinity algorithm, based on
freshwater discharge and cross-sectional area of the estuary, to
model saltwater intrusion in river-dominated estuaries of our study
domain.
• Model inputs included the USGS
LiDAR-derived elevation data (vertical accuracy: 12 cm)
NOAA tidal data
Accretion rates
National Wetlands Inventory (NWI) data
Study area – lower Pascagoula River Estuarine
9th American most endangered rivers
Latitude 30º28’N
Longitude 88º35’W
Accretion rates
Type of wetland
Location
Sampling dates
Sediment
Accumulation
(cm /y)
Freshwater tidal
marsh
N 30° 28’ 39.20’’
W 88° 35’ 56.50’’
11/7/2009
0.45 ± 0.20
Brackish marsh
N 30° 26’ 5.46’’
W 88° 35’ 19.14’’
4/25/2010
0.51 ± 0.30
Salt marsh
N 30° 21’45.85’’
W 88° 36’ 35.28’’
10/7/2010
0.30 ± 0.19
From fallout radionuclides (7Be, 137Cs, and 210Pb)
Sea level rise scenario
Sea level rise rate is predicted to be 0.10 inch/year to
0.83 inch/year, on Mississippi Gulf Coast, which will
be translated to 0.26 m to 2.19 m increase in sea
level from 1996 to 2100.
• High sea level rise scenario
• Low sea level rise scenario
Landscape metrics
1996
2100 under high
SLR
2100 under low
SLR
Edge density
685.0268
377.5212
841.2947
Perimeter/Area
14285.7143
10714.2857
11904.7619
Contiguity index
0.0833
0.1667
0.1667
Aggregation index
90.4273
94.7288
88.2405
Patch richness
density
0.0316
0.0380
0.0380
Shannon’s diversity 1.4808
index
0.9620
1.5657
From 1996 to 2100
High
low
Low vs. High sea level rise scenario in 2100
• Simulate the impact of changes in coastal wetland on
storm surge
Method
• Advanced CIRCulation (ADCIRC model).
Sea, Lake, and Overland Surges from Hurricanes (SLOSH) model:
domain is limited and the spatial resolution is very coarse (0.5-7 Km)
(International Hurricane Research Center, online). It is difficult to
simulate convoluted shorelines and incorporate features that block or
accelerate storm surge flooding. In addition, tide and wave set ups are
not included, and the overland flooding model is not adequate, thus
SLOSH tends to produce large uncertainty and provides only a very
rough estimate in the predicted flooded area only.
ADCIRC’s domain is flexible, its spatial resolution can reach finer than
50×50 m, it can simulate convoluted shorelines and include features
like highways and canals, and it contains tide setup, so it performs
better (albeit more slowly) than SLOSH, especially at the shoreline.
Mesh and bathymetry
Storm surge 1996
Water elevation in 1996
Water elevation in 2100 under high SLR scenario
Water elevation in 2100 under low SLR scenario
1996
2100 under high SLR scenario
2100 under low SLR scenario
Conclusion
• SLR is likely to affect area and distribution of coastal
wetlands and therefore alter landscape patterns.
• Wetland change due to SLR is likely to change storm
surge height (e.g. 1.8 -8.5% increase under different
scenarios of SLR) and affect the pattern of coastal floods
(increase the flooded area).
Acknowledgements
Mississippi-Alabama Sea Grant Consortium Program
Development
Mississippi-Alabama Sea Grant Consortium Coastal
Storm Program
Thank you!