FLOOD06541

• County: Garfield
• Community: Carbondale, Marble
• Stream Name: Crystal River
• Basin: Colorado Mainstem
• Title: Marble Community File
• Date: 1/1/2001
• Prepared For: CWCB
• Prepared By: CWCB
• Floodplain - Doc Type: Community File

CHA!'\LES S. ROBINSON AND ASSOC., INC.

Consulting Geologists and Engineers

SotS South Union Blvd. Den....er. Colorado 80228

Phone: [phone]
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November 2, 1972

r1r. Don \'/e i xe 1 man
Continental Realty West
3200 East Mulberry Street
Fort Collins, Colorado 80521

Dear Sir:

At this time I should like to review the conclusions from the
inspection trip made to the t'larble Ski Area on October 25, 1972.
The trip \"Ias made in the company of f1ichael K. Barrett, of Ketchum-
Konkel-Barrett-Nickel-Austin, Richard C. Hepworth of Chen and Assoc.,
and yourself. The purpose of the trip was to review' the geologic
and engineering problems related to the Slate Creek drainage and the
development of the Marble Ski Area..

Slate and Carbonate Creeks are tributaries to "the Crystal River,
which forms the local base level for these streams. Before the pub-
lic development of the Crystal River Valley--chiefly the establish-
ment of the town of Marble--these streams flowed from deeply eroded
valleys OJ~ across an alluvial fan to the Crystal River. The allu-
vial To;; ,,2.S formed by the streams as a result of a change in gra-
dient fro~ the steep mountain vallies to the relatively flat valley
of the Crystal River. Each stream would build a channel flanked
by natural levies on the alluvial fan. At times of flooding, the
streams would breach their levies and form a new channel; and they
repeated this process again and again. It is in this way that allu-
vial fans are built. The sources of the material to build the fans
are the steep walls of the valleys at the head of the streams, and
the sides of the upper part of the stream vallies as they erode their
channels toward the base level of the Crystal River Valley.

At some time in the recent past, reportedly in the 1920's, the
citizens of Marble diverted Slate Creek from a general southeasterly
course to a southwesterly course. The purpose was to divert the
periodic floods, or mud flows, away from the town of Marble. The
result was to increase the gradient of Slate Creek. Slate Creek has
cut a channel 30 to 50 feet deep into the existing alluvial fan for
almost half a mile below the point of diversion. Slate Creek issues
onto a relatively flat area above the county road serving the town of
Marble. In this area, there have been almost annual mud flows as
the result of flooding of Slate Creek. All along the present channel
of Slate Creek is evidence that the banks of the stream are period-
ically topped by floods. Most of the material that forms the mud flows
along the lower reaches of Slate Creek is believed to be derived
from erosion of the channel of Slate Creek--erosion which was accel-
erated by the diversion of Slate Creek and the increase in gradient.
! "
It is estimated on the basis of the geologic mapping of the

area that any part of the Carbonate-Slate Creek alluvial fan is subject