WSP00519

• File Number: 5000.300
• Description: Flood Protection Section - Mudflow Mitigation Plan - 1987
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 1/1/3000
• Author: Unknown
• Title: Landslide Areas - Date Unknown
• Water Supply Pro - Doc Type: Report/Study

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000667

avalanches are produced in colluvium of the sides lopes of mesas and
become channelized debris flows that.can move as far as two miles down
the foots1opes.

Douglas County is currently the newest and fastest growing county of the
Colorado Front Range Urban Corridor. In anticipation of this future
explosive growth, the CGS did quadrangle-level geologic hazards mapping
of the county in 1978. This mapping is very adequate for local land-use
decisions and mitigation planning.

9) 8ig Thompson River tributary streams from Estes Park to Loveland. This
basin was the site of the catastrophic Big Thompson flood of 1976. The
area was studied and mapped by CGS immediately following the flood. This
event was of particular interest because it graphically showed the
interplay of mainstream flooding with repeated debris-flow activity from
smaller tributary streams that occurs in mountain torrent flooding. We
believe that under similar conditions a very large number of Colorado's
mountain basins are capable of such extremely destructive events. The
geologic hazard maps produced by CGS in 1976 are adequate for planning
and redevelopment decisions in the area.

10) This alpine region is subject to
mu tlp e azar s lnc u 1ng ava anc es, landslides, and debris flows. No
general geologic hazards mapping is available and should be done.
Studies for a new ski area on the West Fork River near the south approach
to the pass resulted in detailed mapping of one very large debris-flow
path by conSultants to the developer. Planning is currently underway for
mitigation to minimize hazards to private property and the highway.
Basic studies and CGS reviews were funded by the ski area developer.

11) Chalk Creek area, vicinit of Mt. Princeton, Hot S rin s, Chaffee
County. T is is an area of existing and expanding recreationa~
development. Much of the area including eXisting development is a fan
with multiple distributaries. Fairly severe rockfall hazards are also
present adjacent to the Chalk Cliffs. CGS has done some informal
geologic hazard mapping and reviewed numerous land-use applications. The
area badly needs formal geologic hazard studies with emphasis on the
debris flows. The study should address mitigation opportunities for
existing development as well as hazard mapping., This work is '
preliminarily scheduled for 1987-88.

12) Arkansas River tributaries between Sa1ida and Canon Cit , Chaffee and
remont Counties. This area is notorious for the many flash-flood and
debris-flow prone tributaries that cause frequent damage in their lower
reaches and fans near the Arkansas River valley. No formal hazard
mapping has been done and is badly needed. Preliminary work could
probably be done with existing photography and field work. The area is
so large that it would probably be broken into two or three projects.

13) Red Cliff town site, Ea le Count, debris avalanches and debris flows.
ur1ng t e urry 0 debr1S- ow act1vlty in centra Eag e CJJnty during
May of 1984 the northern part of Red Cliff experienced a succession of
severe debris flows from one ravine. At the request of town, county and
State Emergency Services officials, CGS did an informal field and photo
reconnaissance of the area. Later we assisted Emergency Services staff

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