WSP06362

• File Number: 8210.470
• Description: Pacific Southwest Interagency Committee
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 11/1/1971
• Author: PSIAC
• Title: Pacific Southwest Analytical Summary Report on Water and Land Resources based on Framework Studies of Four Regions - November 1971
• Water Supply Pro - Doc Type: Report/Study

OOa&89 .

considered for future construction include flood
control among their various multiple purposes.
Flood control storage will increase from the
existing 18.2 million acre-feet to 28.2 million
acre-feet by 1980, to 35.3 million acre-feet by 2000,
and to 38.2 million acre-feet by 2020. The projected
flood control storage requirements by region are
shown in table 8.
Levees and Channels. - Levees protect a iocal area
from flood losses by restricting the area of overflow.
Improvements to channeis consist of widening,
deepening, straightening, clearing of obstructions, and
lining with concrete or other material to increase flow
efficiency. The program of levee construction and
channel improvements for the four regions of the
Pacific Southwest is shown in table 9.
Watershed Treatment. - Watershed treatment
prevents excessive erosion and subsequent debris
deposition, and improves the hydrologic functions of
watersheds. Measures include flood detention
reservoirs, dikes, and channels (included in
tabulations for levee and channel programs), contour
trenching, terracing, furrowing, gully plugs, revegeta-
tion, and other soil-stabilization practices. The total
amount of land involved in the physical watershed
treatment program planned primarily to reduce ero-

Flood Control

sion and sediment production in the interest of
flood control is shown in table 10.
Flood Plain Management. - The Federal Flood
Plain Management Services Program provides
informs tion on flood hazards which guides local
authorities in determining the use of flood plains.
Flood plain information studies have been completed
or are authorized for many urban areas with potential
flood problems in the four regions of the Pacific
Southwest.
Improved Flood Forecasting. - Improvements in
the flood forecasting system are included in the plan.
These include: (1) expansion of the data reporting
network; (2) increased use of satellite capability;
(3) increased and expanded radar coverage; (4) more
community flash.flood alerting programs;
(5) upgraded computer facilities for more rapid
processing of data and increased research capabilities;
(6) improved daily river forecasting capabilities on
major rivers; and (7) expanded research for better
hydrologic models.
Other measnres. -Other flood control measures
include flood fighting, floodway regulation, flood
plain zoning, flood proofing, flood plain insurance,
temporary evacuation, subdivisIon regulation,
restrictive building codes, and health regulations.

Table 9.-Levee construction and channel improvements

1965-1980 1980-2000 2000-2020 1965-2020
Region Levee Channel Levee Channel Levee Channel Levee Cha.onel
(Length in miles)
California 549 1,238 521 786 835 486 1,905 2,510
Great Basin 20 103 36 74 42 36 98 213
Lower Colorado 273 586 71 384 94 151 438 1,121
Upper Colorado ..J! 3 7 8 2 0 9 11
Pacific Southwest 842 1,930 635 1,252 973 673 2,450 3,855

Table I O.-Land involved in watershed treatment
Region 1965-1980 1980-2000 2000-2020 1965-2020
(Millions of acres)
California 1.2 1.8 1.3 4.3
Great Basin 0.2 0.3 0.2 0.7
Lower Colorado 2.9 4.1 2.6 9.6
Upper Colorado 2.4 3.1 1.6 7.1
Pacific Southwest 6.7 9.3 5.7 21.7

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