FLOOD03422

• County: Statewide
• Community: na
• Basin: Statewide
• Title: Flood Hazard Mitigation Plan
• Date: 2/1/1998
• Prepared For: State of Colorado
• Prepared By: CWCB
• Floodplain - Doc Type: Flood Mitigation/Flood Warning/Watershed Restoration

1998. Colorado Rood Hazard Mitigation Plan (409)

The causes of floods relate directly to the accumula-
tion of water from precipitation or the failure of man-
made structures such as dams or levees_ Floods
caused by precipitation are further classified as com-
ing from:

. Rain in a general stann system

. Rain in a IocaJized intense thunderstonn

. Me/ting snow

. Rain on melting snow

. Ice jams

Rainfall and metting snow in the mountains feed four
major river systems with headwaters in Colorado,
These are the_ Missouri, Arkansas, Rio Grande, and
Colorado River basins_ These basins encompass
many small streams and rivers as shown in Figure
2.2_

Precipitation in each basin is related to the seasons
and two major sources of moisture_ Summer showerll
and thunderstorms that occur from June througn

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101'

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101'

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Figute 2.2

108'

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September primarily are caused by moisture from the
Gulf of Mexico or the Pacific Ocean_ During the fall,
occasional general rainstorms and thunderstorms 0c-
cur from wet and warm cyclonic air masses, which
move in from the southern Pacific Ocean_ Winter and
spring rain and snow storms are generally a result of
moist air masses which originate in the cooler northem
Pacific Ocean and move inland across the Pacific
Northwest

Floods caused by failure of manmade structures are a
result ot

. Hydrologic deficiencies

. Structural deficiencies

. Improper Opetation or Sabotage (1 case in CO)

Each of these causes results in floods, which have
distinct characteristics relative to rate of rise, volume,
duration, and flood season_

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39'

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38'

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File:FHJ6P.Chapter.2.puI>

ChaptJlf2.2

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