FLOOD01659

• County: Statewide
• Title: Floodplain Management Handbook
• Date: 9/1/1981
• Prepared By: Flood Loss Reduction Associates
• Floodplain - Doc Type: Floodplain Report/Masterplan

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Diversions

Diversions intercept flood flows
upstream of a damage-prone area and
route them around the area through an
artificial channel. Diversions may
ei ther completely reroute a stream or
only collect and transport flows that
exceed the normal capaci ty of the
channel or that would cause damage.

,

Flood problems can sometimes be
solved by rerouting a stream away
from developed areas. The channel
on the right diverts high flows
around the developed area.

"

Diversions sometimes offer the
advantage of protecting several nearby
communi ties with one major facility. A
negative aspect is the false sense of
security which may prevail in the
"protected areas".

Diversions are particularly well
suited for protecting developed areas
because they don't require land
acquisition or construction within the
protected area. However, opportunities
for diversions are often limited by the
nature of local land formations and
soil conditions. There must also be a
stream channel available into which the
di version can empty. The recei ving
channel must have enough capacity to
carry the flow disposed of through the
diversion without causing flooding.

Also, the use of diversions may be
limited in some states by laws pro-
hibiting transfer of water between
basins or watersheds.

Land Treatment

Land treatment measures are used
to reduce runoff of water to streams or
other areas. Techniques of land treat-
ment include maintenance of trees,
shrubbery and vegetative cover,
terracing, slope stabilization, grass
waterways, contour plowing and strip
farming. These measures reduce water
flow by improving infiltration of rain-
fall into the soil, slowing and
reducing runoff, and reducing the
sedimentation that can clog stream
channels or storage reservoirs. While
the effect of any individual measure is
small, extensive' land treatment
programs can effectively reduce flood-
ing in small headwater areas. Land
treatment measures are less effective
in downstream areas subject to larger
floods.

Terracing of slopes reduces runoff
and improves groundwater recharge.
It also helps prevent erOSIOn and
consequent downstream sedimentation.

Land treatment measures are most
commonly used in agricultural areas. In
areas with steep slopes and unstable
soils, maintaining a good growth of'
grass and other vegetation is the rr.ost
practical way of reducing runoff and
erosion. Several land treatment

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