FLOOD09387

• County: Statewide
• Basin: Statewide
• Title: Flood Fighting Instructions
• Date: 1/1/1991
• Prepared By: US Army Corps of Engineers
• Floodplain - Doc Type: Flood Mitigation/Flood Warning/Watershed Restoration

OM SOO-I-6
January 1991

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foundation conditions, action of rodents, inadequately engineered alterations,
or a serious accident may result in a levee break. Foundation failures can
result in sand boils and possibly a sinking levee. Poor construction methods
and the use of unsatisfactory material cause slides and sloughs. However, such
threatened failure can be overcome if prompt action is taken and proper methods
of treatment are used. Wave wash is to be expected whenever the levee is exposed
to a wide stretch of open water and, if permitted to continue over a considerable
length of time, will develop into a serious xhreat. Streams in mountainous and
hilly areas tend to have very high velocity flood flows which can rapidly erode
unprotected levees.

5. Premeditated Damage. The person in charge should continually guard against
premeditated damage to the levee. In the event of an extraordinary flood
requiring a fight over long stretches of levees on both sides of streams there
is a natural temptation to relive the strain by breaking the opposite levee.

6. Human Element. Panic does not directly endanger levees, but psychological
fear due to ignorance of actual conditions may seriously affect the high-water
fight during a critical moment. This fact should be considered in organization
for emergency work. Confidence, engendered by an efficient organization, free
from local jealousies, is the best guard against panic. Rumors of upstream levee
breaks or higher than actual flood crests can also cause panic. Good
communication and reliable factual information can avoid rumors,

4IJ 7. Standard Methods. For Treating Various Defects.

a. General. If possible, levee patrols should be initiated before arrival
of a predicted flood (i.e., major snowmelt runoff), Access routes, travel time,
bridge capacities, known problem areas should be examined. The methods of
treatment outlined in the following paragraphs have been used by the Corps and
have proven to be effective, Appendix B contains sketches of recommended
methods.

b. Drainage of Slopes. This work can be done economically while awaiting
developments and will serve to make the levees more stable and efficient. Crews
should be organized to cut seep drains at all places on the landslide levee slope
and berm where seepage appears, The drains should be V-shaped, no deeper than
necessary. and never more than six inches deep. In all instances, drains should
be cut straight down the levee slope or nearly so. Near the toe of the slope
the small drains should be Y'd together and led into larger drains, which, in
general, should lead straight across the landslide berm into the landslide pits
or main lateral ditch. If the levee becomes saturated and sloughs occur, see
paragraph e.

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c. Setback Levees, Setback Levees are smaller levees built to the
landslide of the main levee for formation of pools to reduce the effective water
pressure on the landslide and thus inhibit the formation of boils and movement
of foundation material. Nearby road or irrigation canal embankments may be at
the proper position and grade to be temporarily incorporated into a setback levee
arrangement. Immediately upon mobilization, siphons or pumps should be put into
operation and kept running until each sublevee basin is filled.

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