Environmental Engineering Reference
In-Depth Information
twenty-three acres of former wetlands have been revegetated, all accomplished at a
total cost of $25 million.
One of the things that Las Vegas is famous for is its demolition and reconstruc-
tion of casinos. The southern Nevada Water Authority has realized that each year,
if they can stockpile and recycle the construction debris from some of this activity,
they can save $10.00-15.00 a cubic yard on large rip-rap at the same time as keeping
the material out of landfills. Therefore, much of the foundation for erosion control
structures installed in the Wash came from those imploded buildings whose original
presence in the city had done much to contribute the stormwater runoff which had
caused the damage in the Wash in the first place (France 2011). This rip-rap was
dumped into the channel bed, followed by revegetation through either natural colo-
nization or deliberate planting by citizen volunteers.
ADAPTIVE MANAGEMENT
In April 2000, the Las Vegas Wash Committee approved a comprehensive adaptive
management plan which would address monitoring channel stabilization, revegeta-
tion, and invasive plant management (France 2011). It was deemed important that the
plan continue to maintain the momentum created over the decades of advocacy, be
very adaptive to accommodate the dynamic system of the Wash, and include a large
focus on biological and environmental monitoring and assessment which would be
integrated with several of the other plans for the Wash. In this respect, adaptive man-
agement through monitoring is important to determine if the corrective measures
have been effective—and, if not, to suggest ways in which to improve conditions
(Scharnhorst 2004).
The revegetation program is an issue of extreme importance for the success of any
wetland restoration project, be it either in Nevada or in southern Iraq. The erosion
control structures have all been specifically designed to optimize the reintroduction
of native riparian species (Scharnhorst 2004). But not all sites are equal, and the
geomorphology and hydrology turned out to be the keys to the revegetation process.
For example, greater success was soon found to occur if small cells of native ripar-
ian and emergent wetland species were intensively managed within what was really
a nonnative matrix, rather than trying to loosely manage the entire area at any one
time. And with respect to some of the invasive species, these were used to create
some stand diversity in terms of canopy height or spacing as nesting habitat for
migratory birds.
Regardless of the wetland restoration project anywhere in the world, invasives are
a major problem due to their insidious presence. In the case of the Wash, there are
three “most wanted weeds” that require constant management (Scharnhorst 2004).
For one of these, for example—tamarisk, which comes from Eurasia—adaptive
management has shown that in order to eliminate the plant, it is necessary to apply
herbicide within fifteen minutes of their being cut or they will seal up and not suc-
cumb. If simply cut and left alone, this amazingly hardy invasive extrudes salt around
it so that other plants cannot compete with it until it is ready to grow back. Further,
tamarisks also pose a double problem in relation to the use of fire clearance as a
management tool in that burning actually helps the plants propagate.
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