1. Introduction
Wetlands are some of the most fragile, yet crucial, ecosystems found in the United States.
Louisiana particularly has hundreds of miles worth of dynamic wetlands along a gradual
slope, which makes them especially at risk of being inundated with high salinity water due
to sea-level rise (SLR) from climate change. SLR has been reported for many years now,
as carbon dioxide (CO2), methane, and other greenhouse gasses have begun to warm the
Earth at a rapid rate (Williams et al. 2002). This rate is only expected to increase due to
increased atmospheric greenhouse levels and arctic ice melt, and by 2100 it is estimated
that the parish of Terrebonne, LA will face ocean water inundation levels of 5.7ft (Strauss et
al. 2015).
Physical water cover is not the only impact that we need to be concerned with, though, as
other factors come into play due to high-salinity water being in such close proximity. Some
of the wetlands along the coast are salt-water or estuarine based, so they may be able to
handle an increase in ocean water, but others are freshwater based, so the introduction of
an increase in salinity could have even more devastating effects or aquatic and terrestrial
flora and fauna. Depending on the type of wetland, effects from erosion can be seen
conservatively within 1000 feet (U.S. Army Corps of Engineers 2005). The effects of sea
spray can be seen within 300 feet (McElfish et al. 2008).
What coastal wetlands in the parish of Terrebonne, Louisiana are at risk of
being lost due to climate change-induced sea level rise (SLR) as predicted by
the NOAA?
Methods
Data Sources
§ATLAS: Louisiana Statewide GIS (LDEQ). 2004. Elevation Map from 1:24,000 DEM
Mosaic. www.atlas.lsu.edu
§US FWS. 2015. Louisiana Seamless Wetlands. http://www.fws.gov/wetlands/Data
§GeoCommunicator. 2000. Terrebonne, Louisiana Geographic Boundary.
http://www.geocommunicator.gov
Literature Cited
Discussion
Contrary to what some may believe when this research question was posed, the
wetlands most at risk of suffering negative effects from sea-level rise by the year 2100
are in the northwestern portion of Terrebonne, Louisiana (Figure 2). That is because
these wetlands have a low tolerance for higher amounts of salinity, as they are
freshwater based, such as freshwater emergent wetlands (medium risk), freshwater
forested shrub wetlands, freshwater ponds, riverines, and lakes (high risk) (Table 1).
Interestingly, the wetlands that have the lowest risk posed against them are towards the
middle of the area of interest (Figure 2), but Figure 1 illustrates that this is because there
appears to be a gradual sloping increase in elevation starting in the lower middle of
Terrebonne and proceeding to the northeastern part of the parish. This is also where the
effects from sea spray and erosion are most apparent (Figure 3) because of the lower
water levels changing their primary influence on the land from a complete change in
environment to a gradual change. The repeated saturation followed by receding water
levels from the tides will cause erosion over time, and the wave action will stir up sea
spray that could pose a threat, especially to terrestrial flora, in low-salinity wetlands.
Studies such as this are becoming ever-more crucial as climate change progresses,
especially when anthropogenic causes are not being remedied quickly enough. This
study specifically takes a broad look at a date quite a ways away so as to show the kind
of damage that can be done to our coastlines. It is the goal of this research to raise
awareness of the risks that wetlands—some of our most crucial ecosystems—will face in
the coming years if major changes are not made to reverse some of the environmental
damage that has already been done.
As seen in Figure 2, the risks only seem to increase towards the northern boundary of
Terrebonne, and the wetlands of Louisiana continue on for many miles to the East, West,
and North. This study only looked at one parish, but there are many others to worry
about, not to mention the risks that coastlines all over to world face due to sea-level rise.
§Williams K., Pinzon Z.S., Stumpf N., Hageman R.P., Raabe, E. A. 2002. Sea-level rise and
costal forests on the Gulf of Mexico. U.S. Geological Survey. 99 (441).
§Strauss B., Tebaldi C., Kulp S . 2015. Louisiana and the Surging Sea. Climate Central,
Princeton.
§McElfish J., Kihslinger R., Nichols S. 2008. Setting Buffer Sizes for Wetlands. National
Wetlands Newsletter, Washington D.C. 30(2)
§U.S. Army Corps of Engineers. 2005. Guidance on Buffers and Ratios. U.S. Department of
Environmental Protection. Protecting and Managing Wetlands Vol. 2, Seattle.
Evaluating Sea-Level Rise (SLR) in the Coastal Wetlands of Terrebonne, Louisiana
Jade Payne1 and Michael Gilbrook2
Office of Interdisciplinary Studies1 and Department of Biology2, University of Central Florida
Results
In order to locate the wetlands that are of high risk of negative impacts due to the
consequences of sea-level rise (SLR), we created a model that considers the potential
impact of inundation, erosion, sea spray, and the sensitivity of the types of wetlands in
Terrebonne, Louisiana. (Figure 1). Before the model was run, pre-processing steps were
conducted such as clipping the initial Louisiana Wetlands data layer to the boundary of
Terrebonne in order to not overwhelm the computer.
Following the necessary pre-processing procedures, the wetlands layer was classified
according to the sensitivity of wetland type to high-salinity water, as shown in Table 1. The
elevation layer was classified according to the threat that any one point would have
concerning a predicted 5.7ft inundation amount (Table 1). The elevation layer was also
used to select only those areas of wetland that are not completely inundated with water,
which then received two different buffers: one to account for erosion (1 mile) (U.S. Army
Corps of Engineers 2005) due to saturation and sediment movement from closer
inundation, and one to account for sea spray due to wave action proximity (0.5 miles)
(Table 1) . Both buffers take into account tidal fluctuation.
After each necessary input layer was ready for the final cell statistical analysis, the sum of
the previous ranks was taken and finally reclassified according to risk level to produce the
final output and the answer to our question (Figure 2).
Figure 1. A model that analyzes the risk that wetlands have due to sea-level rise,
accounting for effects of inundation, sensitivity of wetland type, erosion, and sea
spray.
Insert Figure Here
Based on the risk model (Figure 1), the wetlands closest to the ocean show intermediate risk due to the impacts
of sea-level rise, with the wetlands further inland appearing to be much more sensitive to this environmental
change (Figure 2). The lowest risk areas are located roughly in the middle of the area of interest (AOI), and this
is important to notice in conjunction with the wetland type and sporadic increases in elevation in these areas
(Figure 3). There are very few tracts of wetland that will be harmed a minimal amount
Figure 2. A map showing the risk that wetlands in Terrebonne, Louisiana face due to impending
sea-level rise by the year 2100.
Figure 3. The risk due to wetland type (Top Left), risk due to
inundation from high-salinity water (Top Right), risk due to
erosion (Bottom Left), and risk due to sea spray (Bottom Right).
Table 1. A table illustrating how each data layer was classified in
the spatial analysis model.
Figure 3, to the left, shows a
graphical representation of the
layers that were inputted into the
model after they had been
classified according to potential
risk from SLR. The most apparent
risk is inundation from high salinity
water as shown in the top right of
Figure 3—It is an elevation-based
layer. Wetland type is more
concerning in the northern portion
of Terrebonne as these locations
are not prone to interacting with
high levels of salinity. The north
eastern part of the parish is where
the effects from erosion and sea
spray play a role, as this is where
the wetlands will not be completely
covered with water, so the gradual
impact of saturation, sediment
movement, and wave action will be
seen towards the edges of the
water line.