FLOOD08745

• County: Statewide
• Community: Statewide
• Basin: Statewide
• Title: Colorado Flood Hazard Mitigation Plan
• Date: 12/1/1999
• Prepared For: State of Colorado
• Prepared By: Kistner and Associates
• Floodplain - Doc Type: Flood Mitigation/Flood Warning/Watershed Restoration

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Colorado Flood Hazard Mitigation Plan -1999

Many of the older mountain communities were built in
part or entirely on the sides 01 major mountain valleys
which are the usual location of the debris fans of
smaller tributary streams, A debris fan is the depasi-
tionalland form produced by successive mud and de-
bris flow depas~s, The towns of Glenwood Springs,
Ouray, Telluride, and Idaho Springs have a long his-
tory of damaging debris and mudflows, The Town of
Marble in Gunnison County was nearly destroyed by
severe flows in the 1 930s and 1940s, and the mining
community of Brownville (near Silver Plume in Clear
Creek County) was engulfed and destroyed by a series
of flows in June 1912,

Much 01 the damage and loss of I~e during the Big
Thompson storm and flood of 1976 was caused by
multiple debris flows from smaller tributary streams,
The 1965, 1969, and 1973 storm and flood events of
the Front Range area produced extensive debris ava-
lanching that originated on steep mesa side slopes of
Douglas County, During the abnormally heavy spring
snowme~ runoff of 1984 in Eagle County, the commu-
nrlies of Vail, Beaver Creek, and Redcliff were im-
pacted by numerous debris flow events, In add~ion to
threats to I~e and residential properties, the mud and
debris flow events produce even more widespread ef-
feets on transportation and other public facil~ies, re-
quiring extensive and costly clean-up and repair annu-
ally throughout Colorado,

Renewed development in mountainous areas of Colo-
rado has increased dramatically in the past 30 years,
driven by the demand for new resort c0m-
munities and second homes, This pres-
sure has led to a tremendous increase in
development of lands vulnerable to severe
to moderate mud and debris flow hazards,
Ident~ication and m~igation of existing
hazards and future recognition of hazards
in advance 01 land use decisions could
save many lives and millions 01 dollars in
property losses in the years ahead,

Damages in Colorado from debris flows
and landslides are known to have
amounted to several millions of dollars,

Several other slides have or are encroaching on a
stream but have not as yet advanced rapidly enough to
cause serious backwater effeets, However, there are
hundreds of somewhat older inactive or semi-active
slides in many areas 01 the state that could be reacti-
vated or accelerated by increased ground moisture,
stream erosion, man.made excavations or nearby
earthquakes, There is particular concern that contin-
ued increase in sotl moisture and sl"'lOVm1ett runoff as
experienced in 1983 and 1984 could lead to reactiva-
tion of some of these slides, such as the one that oc-
curred at Thistle, Utah, in 1983 w~h serious conse-
quences.

Buffalo Creek Flood Event (1996) - In May 1996, a
wildland fire burned about 12,000 acres of forested
area in the Buffalo Creek vicinity, The fire bumed in-
tensely and quickly, leaving behind charred timber and
a barren landscape devoid 01 vegetation and ground
cover. The burned soils exhib~ed hydrophobic (water
repelling) properties, and the burned area's natural
erosion control and runoff inhibiting characteristics
were altered by the fire. Those cond~ions, in conjunc-
tion with a heavy rainstorm on July 12, were the recipe
for disaster in Buffalo Creek,

On the night of July 12, 1996, a thunderstorm occurred
in the area of the community of Buffalo Creek, Colo-
rado, The storm produced heavy precip~ation over a
short period of time, A flash flood occurred along Buf-
falo Creek, Sand Draw, Spring Gulch, the North Fork
of the South Platte River (North Fork) below ~s conflu-

1999 Flood Disaster Stream Data

River

Date Flood Crest
Stage
April 30, 1999 8 Feet 11.7 Feet
April 30, 1999 7 Feet 11.8 Feet
May 1, 1999 10 Feet 12,5 Feet
April 30, 1999 7 Feet 10,5 Feet
May 1, 1999 9 Feet 11,3 Feet
May 2, 1999 10 Feet 15.6 Feet
May 2, 1999 10 Feet 13.9 Feet

Fountain Creek
@ Colorado Springs

Fountain Creek
@ Fountain

Fountain Creek
@ Pueblo

2.3.3 Catastrophic Landslide
Damages
Catastrophic landslides capable 01 dam-
ming major streams have been relatively
rare in Colorado during the historic period,
The most serious example is probably the
DeBeque Canyon slide of June 1924,
which temporarily blocked the Colorado
River and resu~ed in forced relocation of a
small commun~y, highway, and railroad,

Arkan.as River
@ Avondale

Arkansas River
@ Fowler

Arkansas River
@ La Junta

Arkan.a. River
@ La. Animas

Source: FEMA Interagency Hazard Mitigation Team Report
July 1999 Figure 2.9

Chapter 2 - 11

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