Introduction to Stream Restoration - Hydro-Environmental Analysis: Freshwater Environments - page 214

Realignment usually removes the natural sinuosity of rivers and streams and removes pool
and rifle areas and natural shoals.

• Diversion Channels: Designed to, as the name implies, divert lows from some area.

Diversion channels are commonly constructed to reduce looding in urban areas and are
commonly prismatic (constant shape, such as trapezoidal, and slope).

• Flood Banks (levees or embankments): Designed to increasing the low capacity of streams

and rivers and reduce overbank lows, thereby protecting loodplain development.

• Control Structures (e.g., dams and weirs): Designed to impound water for a variety of pur-

poses such as water supply, irrigation, recreation, hydropower, or other uses.

An example of a channelized river is the Kissimmee River, Florida (Figure 8.3). The Kissimmee
River was originally about 100 mi. long between Lake Kissimmee and Lake Okeechobee. It
is the largest tributary to Lake Okeechobee, supplying about one-half of its inlow. The dis-
tance between these two lakes is only approximately 50 mi., indicating the degree of winding
of this river. In addition, the river had a large loodplain, which was inundated most of the time
(Audubon 2005).
In response to deadly hurricanes in the 1920s, the Central and Southern Flood Control Project
was constructed with the design intended to reduce looding, resulting in the channelization of the
Kissimmee River. The main canal (C-38) constructed was 30 ft. deep and 110 yd. wide; at least
three times the width and depth of the natural river channel (USACE 1991). As a result of the proj-
ect, more than 30,000 acres of wetlands were lost, resulting in the decline of a variety of wildlife,
including waterfowl and bald eagles. In addition, channelization, such as its impacts on increased
velocities, resulted in an increase in pollutant loads to Lake Okeechobee, causing eutrophication of
that waterbody. A variety of restoration projects have been completed or are underway to restore
the system, such as by removing structures and restoring its natural sinuosity (Audubon 2005). At
the time of its authorization, the Kissimmee River restoration was the largest and most expensive
restoration ever attempted.
Currently, there are approximately 235,000 mi. of channelized streams and rivers in the United
States and only approximately 2% of U.S. rivers are natural or relatively undisturbed (American
Rivers 2009). There are over 2.5 million dams in the United States (Johnston Associates 1989),
with 600,000 stream miles under reservoirs (Echeverria et al. 1989). In addition to channeliza-
tion, there has been an approximately 50% nationwide reduction in wetlands, a 98% loss in ripar-

Before channelization After channelization

FIGURE 8.3 Kissimmee River before and after channelization. (From USACE, Kissimmee River
Restoration, U.S. Army Corps of Engineers Jacksonville District, Jacksonville, Florida, 2008, Available at
http://www.saj.usace.army.mil/Divisions/Everglades/Branches/ProjectExe/Sections/UECKLO/KRR.htm.)