[StBernard] NASA DEVELOP: Louisiana Ecological Forecasting

Westley Annis westley at da-parish.com
Fri Nov 2 07:51:07 EDT 2012


NASA DEVELOP: Louisiana Ecological Forecasting

Thursday, November 1st 2012
By Ross Reahard

The Concern

Southeast Louisiana, including St. Bernard Parish (Figure 1), is very
susceptible to tropical cyclones and high water caused by seasonal flooding
events. Continued degradation of coastal forests and wetlands causes St.
Bernard to lose more of its natural protective barriers, which in turn,
exposes it to greater water inundation risk. In 2005, Hurricanes Katrina
and Rita severely damaged many ecosystems that served as natural barriers,
which provided protection against the human and non-human populations of St.
Bernard Parish. In order to protect the communities within St. Bernard
Parish, restore coastal biodiversity, and provide measures to counteract
coastal land loss, it is imperative that these vital coastal ecosystems be
rebuilt. Volunteer groups, non-governmental organizations (NGOs) and
government entities often work separately and independently of each other
and use different sets of information to choose the best planting sites for
restoring coastal forests.

Loss of coastal forests has not only increased the vulnerability of human
populations to storm impacts but has also, through the conversion of swamp
and marshland to open water, decreased the amount of biodiversity in the
parish. Cypress-tupelo swamps, as well as marshlands, provide vital habitat
to several threatened or endangered species such as the brown pelican
(Pelecanus occidentalis), bald eagle (Haliaeetus leucocephalus), whooping
crane (Grus americana), and the Louisiana black bear (Ursus americanus
luteolus).

In the early 1960s, when the Mississippi River Gulf Outlet (MRGO) canal was
dredged as a connection from New Orleans to the Gulf of Mexico via Breton
Sound, it resulted in a dramatic increase in salinity, which led to the
destruction of thousands of acres of wetlands east of New Orleans. The MRGO
canal was intended to help the area prosper economically, but instead it has
only added to the numerous issues that plague this region. The construction
of the MRGO has both directly and indirectly led to major damaging effects
to its surrounding ecosystems, including land loss, erosion, increases in
salinity, and habitat shifts and degradation. The U.S. Army Corps of
Engineers estimated a loss of 1,500 acres of cypress swamps, as well as
damage to 10,300 acres of brackish marsh, 4,200 acres of saline marsh, and
3,400 acres of fresh/intermediate marsh [1], as a result of the construction
of MRGO. The resultant damage and loss that has occurred has, in part, been
due to the fact that, in certain areas, the MRGO has expanded beyond its
designed width of 650 feet, to over 3,000 feet, primarily through erosion of
the banks. This has enabled saltwater to further permeate inland. By the
time the MRGO was completed in 1965, the saltwater intrusion, on average,
increased the salinity from 3.5 ppt (1959 to 1961) to 12 ppt, which resulted
in killing and/or damaging over 600 hectares of swamp forest.

The Science

For this project, using NASA Earth Observing Systems (EOS), Natural
Resources Conservation Service (NRCS) soil surveys, ancillary road and canal
data, along with ground truthing, a comprehensive geographic information
system (GIS) to help identify suitable planting sites for baldcypress and
several other wetland tree species in St. Bernard Parish was created.

The team began by identifying the location of suitable soil types for
planting in St. Bernard Parish. Soil types were classified and rated on a
scale of 0 to 4, where 4 was the most suitable soil rating for the
particular tree species of interest (Figure 2). Using the detailed
descriptions of local soil types published in a report by the United States
Department of Agriculture (USDA) [2], a soil suitability index was created
for each of the 14 trees defined by the report as native to the parish. The
most suitable soil types for each species were indexed as "4 - Well Suited."
The descriptive soil unit section of the report also contains information
about which soil types are saline and which are brackish. These soil types,
as well as those labeled as Urban and Dumps, were given a suitability index
of "0 - Not Suited" for all tree species. Then, the intermediate ratings of
"1 - Poorly Suited," "2 - Fairly Suited" and "3 - Moderately Suited" were
established by comparing the characteristics (water table depth, salinity,
texture, etc.) of the preferred soil types for each tree species. From these
data, researchers created a chart (Table 1) to visually display soil
suitability for each tree species.

Elevation data, in the form of a pre-processed Digital Elevation Model (DEM)
at 1/9 arc-second (approximately 3 meters) spatial resolution, were obtained
from the USGS National Elevation Dataset (NED) through the National Map
Seamless Server (NMSS). Accurate, high resolution elevation data were
integral to the project because elevation is a key factor in determining
suitable planting sites for baldcypress; this is because the tree grows best
at elevations of 2.5 to 6 feet, or about 0.5 to 2 meters. Then, for ease of
analysis and to create an easy to interpret final product for the end-user,
the DEM was recoded (Figure 3) to show elevation values using half-meter
increments.

TIGER roads shapefiles, a standard GIS product from the Census Bureau, which
contain transportation infrastructure data, were downloaded from the U.S.
Census Bureau. The TIGER roads shapefile was quality checked, updated and
edited to show highways, streets and private access roads with differing
symbology. Access to transportation infrastructure is an important
consideration for the end-users who are responsible for selecting potential
planting sites since large amounts of trees and equipment must often be
moved from a staging area to the final planting site. Parish boundary and
water body shapefiles were downloaded from LSU Atlas Statewide GIS server.
The team also created a point shapefile, showing the location of pumping
stations in the study area. Pumping stations drive freshwater, largely from
urban runoff, into areas outside of the levee protection. While in the
field, the DEVELOP team observed relatively healthy stands of baldcypress in
close proximity to the pumping stations. This observation suggests that
these locations create suitable habitats for the trees, most likely because
of the discharge of freshwater into brackish or more saline environments;
additionally, the roots of baldcypress seedlings require constant inundation
with freshwater for proper development.

For the years 2010 and 2011, Airborne Visible/Infrared Imaging Spectrometer
(AVIRIS) imagery was obtained from the NASA Jet Propulsion Laboratory's
(JPL) AVIRIS 2006-2010 Flight Data Locator. The processing procedure for
the hyperspectral AVIRIS data cube predominantly followed methods outlined
by Spruce et al. [3] [4]. To create a land cover classification map, the
data were first spatially and spectrally subset to a working extent using 15
of the 224 available channels that effectively discriminate vegetation cover
types (Table 2). The 30 classes were analyzed by overlaying the classified
image on the original 3.5m true color composite and recoded into 4 groups:
water, marsh, forest/scrub, and urban (Figure 4).

AVIRIS data from a single low altitude swath were also processed to
calculate a Red Edge Normalized Difference Vegetation Index (NDVI). This
analysis was conducted to highlight the robust capabilities of AVIRIS, as
well as demonstrate to end-users one potential method of monitoring restored
vegetation health. AVIRIS data from May 5, 2010 were atmospherically
corrected and calibrated from radiance to reflectance using the QUick
Atmospheric Correction (QUAC) method in ENVI Classic. The Red Edge NDVI, a
narrowband greenness vegetation index modified to focus on reflectance
values along the red edge, was calculated through the Vegetation Index
Calculator in ENVI. This index uses greenness values as a proxy for
vegetation health and vigor and is thus contingent upon the time of year
that the data are collected. However, if used responsibly, this index can
yield valuable information on stand health at very small spatial scales.
Then, after the planting process is complete, vegetation indices, such as
NDVI, can easily be calculated by end-users to monitor spatio-temporal
trends in the health of restored forests.

In order to extend the analysis of coastal forests into the pre-space-borne
era of earth observations, historic aerial photography was obtained from
USGS's Earth Explorer. The historic images were used to estimate the spatial
extent of forested land pre-MRGO (Figure 5). Imagery collection dates
include April and May of 1952 and February of 1956. Following acquisition,
the historic imagery was cropped, georeferenced and mosaiced together
through the use of ArcMap and ERDAS Imagine software. Features such as image
texture and shadowing were used to help delineate forested from non-forested
land.

The Benefit

The Louisiana Ecological Forecasting team partnered with several local
non-profit groups including the Wetlands Tree Foundation, St. Bernard
Wetlands Foundation, and The Meraux Foundation. These groups are directly
involved in potting and raising baldcypress seedlings and other native tree
species and work extensively with volunteer groups to conduct plantings.
Often, local knowledge is the main deciding factor when choosing where to
plant. Parish politics and land ownership issues sometimes prevent access
to suitable sites. The DEVELOP team was able to provide our partners with
unbiased scientific information (Figure 6) on the best-suited locations for
baldcypress tree planting, and the ultimate expected outcome is that the
planning process, as well as the in-the-field work, can be streamlined.

The DEVELOP team also partnered with the St. Bernard Parish Planning
Commission's Coastal Advisory Board. The Parish Planning Commission is very
interested in including the DEVELOP team's results in its upcoming master
plan. A team member is also scheduled to present the team's findings at the
Planning Commission's next meeting in October 2012.

Benefits of this work should be seen almost immediately. Seedlings will
begin to go into the ground in early spring, and the maps created by DEVELOP
will guide where the trees are planted. Not only will there be an immediate
impact, but the results will continue to help guide coastal reforestation
efforts into the foreseeable future. In addition, the basic methodology we
developed can be easily tailored to fit a variety of other coastal
restoration applications, which further demonstrates the usefulness and role
NASA EOS can have in rebuilding coastal Louisiana.

Results from this project have already been presented to project partners at
Stennis Space Center and were featured in the summer DEVELOP close-out
presentation given at NASA Headquarters in Washington, D.C. The project was
awarded first place in a virtual poster session sponsored by Esri and hosted
on Institute of Electrical and Electronic Engineers' (IEEE) Earthzine
website. The team has also submitted this project's abstract for possible
presentation at the American Geophysical Union's Annual Fall Meeting in San
Francisco, as well as the Bays and Bayous Symposium in Biloxi, Mississippi.

Figures/Charts available here:
http://www.directionsmag.com/articles/louisiana-ecological-forecasting/28516
0




More information about the StBernard mailing list