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<br />Colorado Flood Hazard Mitigation Plan - 1999 ==:==-
<br />
<br />River
<br />Fountain Cr..ek
<br />@ Colorado Spring
<br />Fountain Cr..ek
<br />@ Fountain
<br />Fountain Creek
<br />@ Pueblo
<br />Arkansas River
<br />@ Avondale
<br />Arkansas River
<br />@ Fowler
<br />Arkansas River
<br />@ La Junta --
<br />Arkansas Ri"..r
<br />@ Las Anima"
<br />Source: FEMA Inter
<br />July 1999
<br />'." . .
<br />
<br />Many of the older mountain communities were built in
<br />part or entirely on the sides of major mountain valleys
<br />which are the usual location of the debris fans of
<br />smaller tributary streams, A debris fan is the deposi.
<br />tional land form produced by successive mud and de.
<br />bris flow deposlls, The towns of Glenwood Springs,
<br />Ouray, Telluride, and Idaho Springs have a long his.
<br />tory of damaging debris and mudflows, The Town of
<br />Marble in Gunnison County was nearly destroyed by
<br />severe flows in the 1930s and 1940s, and the mining
<br />communlly of Brownville (near Silver Plume in Clea'
<br />Creek County) was engulfed and destroyed by a series
<br />offlows in June 1912,
<br />
<br />Much of the damage and loss of life during the Big
<br />Thompson storm and flood of 1976 was caused by
<br />multiple debris flows from smaller tributary streams,
<br />The 1965, 1969, and 1973 storm and flood events 01
<br />the Front Range area produced exten:;ive debris ava-
<br />ianching that originated on steep mesa side slopes 01
<br />Douglas County, During the abnormally heavy spring
<br />snowmell runoff 01 1984 in Eagle County, the commu-
<br />nities of Vail, Beaver Creek, and Redditt were im-
<br />pacted by numerous debris flow event~i. In addition to
<br />threats to IlIe and residential properties, the mud and
<br />debris flow events produce even more widespread el-
<br />fects on transportation and other public facilities, re-
<br />quiring extensive and costly clean-up and repair annu-
<br />ally throughout Colorado,
<br />
<br />Renewed development in mountainous areas of Colo-
<br />rado has increased dramatically in the, past 30 years,
<br />driven by the demand for new resort com-
<br />munities and second homes. This pres-
<br />sure has led to a tremendous increasB in
<br />development 01 lands vulnerable to severe
<br />to moderate mud and debris flow hazards,
<br />Identification and mitigation of exls':ing
<br />hazards and future recognition of hazards
<br />in advance of land use decisions cCluld
<br />save many lives and millions of dollam in
<br />property losses in the years ahead,
<br />
<br />Damages in Colorado from debris flows
<br />and landslides are known 10 have
<br />amounted to several millions of dollars,
<br />
<br />2.3.3 Catastrophic Landslide
<br />Damages
<br />Catastrophic landslides capable 01 dam,
<br />ming major streams have been relatively
<br />rare in Colorado during the historic period,
<br />The most serious example is probably the
<br />DeBeque Canyon slide of June 1924,
<br />which temporarily blocked the Colorado
<br />River and resulted in forced relocation of a
<br />small communlly, highway, and railroad,
<br />
<br />Several other slides have or are encroaching on a
<br />stream but have not as yet advanced rapidly enough to
<br />cause serious backwater effects. However, there are
<br />hundrecls of somewhat older inactive or semi-active
<br />slides in many areas of the state that could be reacti-
<br />vated or accelerated by increased ground moisture,
<br />stream erosion, man-made excavations or nearby
<br />earthquakes. There is particular concern that contin-
<br />ued increase in soil moisture and snowmelt runoff as
<br />experienced In 1983 and 1984 could lead to reactiva,
<br />ticn of some of these slides, such as the one that oc-
<br />curred at Thlslle, Utah, in 1983 wllh serious conse-
<br />quences.
<br />
<br />i Buffalo Creek FI()()d I:vent (1996) - In May 1996, a
<br />wildland lire burned about 12,000 acres 01 lorested
<br />area in the Buffalo Creek vlcinlly, The fire burned in-
<br />tensely and quickly, leaving behind charred timber and
<br />a barr€!n landscape devoid of vegetation and ground
<br />cover, The burned soils exhibited hydrophobic (water
<br />repellin[1l properties, and the burned area's natural
<br />erosion control and runoff inhibiting characteristics
<br />were altered by the fire, Those conditions, in conjunc-
<br />tion with a heavy rainstorm on July 12, were the recipe
<br />for disaster in Buffalo Creek.
<br />
<br />On the night of July 12, 1996, a thunderstorm occurred
<br />In the area 01 the community of Buffalo Creek, Colo-
<br />rado, The storm produced heavy preciprtatlon over a
<br />short period of time, A flash flood occu""d along Buf-
<br />raio Creek, Sand Draw, Spring Gulch, the North Fork
<br />of the South Platte River (North Fork) below lis conflu-
<br />
<br />" ,
<br />
<br />ad Disaste
<br />
<br />Date
<br />
<br />Flood
<br />Stage
<br />
<br />6 Feet
<br />
<br />,;
<br />,
<br />
<br />Crest
<br />
<br />1:
<br />
<br />April 30, 19119
<br />
<br />11,7 Feet
<br />
<br />s,
<br />
<br />April 30, 19119
<br />
<br />7 Feet
<br />
<br />11.6 Feet
<br />
<br />i'
<br />,
<br />
<br />May 1,19119
<br />
<br />10 Feet
<br />
<br />12.5 Feet
<br />
<br /> _.-
<br />April 30, 19119 7 Feet 10.5 Feet
<br />May 1, 19!19 9 Feet 11,3 Feet
<br /> ---- ----
<br />May 2, 19119 10 Feet 15.6 Feet
<br />May 2, 19EI9 10 Feet 13.9 Feet
<br />
<br />lIgeney Hazard Mitigation Team lReport
<br />Figure 2.9
<br />W~il$.a".l)!,l"" ..I!!<*~i\-""-.J~~;K"~~Mf~I,,,lj;j-j!'4t""~';'fliilt5l~liffli""I,!;f'i' ,"lr:.1'~~~>I'I~~1' _I ;.,-"".'
<br />
<br />Chapter 2 - 11
<br />
<br />12/23/9910:00 PM
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