Environmental Engineering Reference
In-Depth Information
14,000 miles identified
(USACE program levees)
9,800 miles detail inventory FY08
(USACE federal levees)
No information on private/other
FIGURE 3.16
Locations from an initial survey to identify all levees in the USACE program. (From
Shoffstall, G.D., USACE Levee Safety Program, New York State Emergency Management Association Winter
Conference, 2009.)
•
Submit, annually, a priority list of lood damage reduction studies and projects
•
Periodically publish an inventory of U.S. levees, including inspection results
The act also established an interagency committee on levee safety to support and coordinate
federal levee safety programs.
As of 2009, the U.S. Army Corps of Engineers had surveyed approximately 14,000 miles of pri-
marily federally owned and maintained levees (Shoffstall 2009), as illustrated in Figure 3.16. That
survey was expanded to greater than 14,700 miles of levee systems by 2012.
3.2.4.2 What Are the Impacts?
As with all such engineered structures, levees may have both positive and negative environmental
effects. For example, levees have by design allowed for the isolation and drainage of wetlands
for other purposes, such as agricultural uses. Levees have also been commonly used, such as in
Louisiana, to isolate and protect wetlands from saltwater intrusion and to restore them. Some addi-
tional impacts include:
•
Loss of riparian vegetation for levees immediately adjacent to the bank or stream edge
•
Loss of sediments and nutrient replenishment by looding
•
Increase in velocities due to channel coninement, resulting in changes in erosional and
sedimentation patterns
•
Isolation of habitats and populations
3.3
CHANNEL MODIFICATIONS
3.3.1 o
VerVIew
The man-made alteration of rivers has been referred to as hydromodiication or river engineer-
ing. Hydromodiication, or river engineering, includes the construction of dams, levees, and other
control structures, as discussed in the preceding section. One additional common goal particularly
of early river engineering projects was either the construction of new channels or the alteration of
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