FLOOD03593

• County: Garfield
• Community: Glenwood Springs
• Basin: Statewide
• Title: Debris-flow Hazard Analysis and Mitigation An Example from Glenwood Springs
• Date: 1/1/1977
• Prepared For: State of Colorado
• Prepared By: USGS
• Floodplain - Doc Type: Educational/Technical/Reference Information

RICHARD D. LAMM
GOVERNOR

JOHN W. ROLD
Director

COLOI~A[)() GEOLOGICAL SURVEY
DEPARTMENT OF NATURAL RESOURCES

715 STATE CENTENNIAL 8U'LDING - 1313 SHERMAN STREET
DENVER, COLORADO 80203 PHONE [phone]

The Honorable Richard D. Lamm
Governor of Colorado

Dear Governor Lamm:

During the past several years, the Colorado Geological Survey
has become increasingly aware of the potential hazards to Colorado
residents from debris flows. These potential hazards became grim
reality in the Big Thompson Canyon and Sweetwater Creek areas during
1976 and in the City of Gl'enwood Springs in July 1977. As part of
our continuing efforts to increase the understanding of the interrelationships
between geologic processes and land-use problems, we retained Mr.
Arthur 1. Mears to analyze the Glenwood Springs debris-flow events.
In the resulting report he has proposed appropriate mitigation measures
for decreasing the future hazard in the affected area. This publication
reports Mr. Mears' specific findings for three deb'ris fans that were
active July 24, 1977. The debris flows and debris flooding resulted
in up to an estimated two million dollars in damages.

The analysis and structural solutions presented herein are specifically
addressed to the present conditions of the debris fans. The three
debris fans have been greatly altered from their natural state by
construction of roads, houses:. and an irrigation ditch. The selection,
placement, height, and st'rength of thE' structural debris catching
fences proposed for mitigation of the hazard are related to the present
man-modified physical cond it ions of the debris f,ans and use of the
hazard area. Although this study is site specific, the methods of
analysis could be applied to similar hazards in other parts of the
State.

Governmental entities having jurisdiction over debris-flow hazard
areas must judge on an individual basis what land-use decision would
be in the best interest of the health, safety, and welfare of the
public. In developed areas with existing high property values, relatively
costly structural protection may be the best alternative to acceptance
of periodic damage to homefi. In this case, restrictions on further
development and reconstruction of badly damaged structures may be

GEOLOGY
STORY OF THE PAST. . . KEY TO THE FUTURE