BOARD02330

• Board Meeting Date: 5/19/2003
• Description: Flood Section - Publishing the 2002 Post-Fire Hazard Identification Maps
• Board Meetings - Doc Type: Memo

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STATE OF COLORADO

Colorado Water Conservation Board
Department of Natural Resources
1313 Sherman Street, Room 72\
Denver, Colorado 80203
Phone: [phone]\
FAX: [phone]
www.cwcb.state.co.us

MEMORANDUM

Bill Owens
Governor

TO:

Colorado Water Conservation Board Members

Greg E. Walcher
Executive Director

FROM:

Larry Lang, Chief, Flood Protection Program
Tom Browning, P.E., Flood Protection Program

Rod Kuharich
CWCB Director

DATE:

Dan McAuliffe
Deputy Director

May I, 2003

SUBJECT: Agenda Item 23.d - May 1, 2003 CWCB Meeting
Publishing the 2002 Post-Fire Hazard Identification Maps

Introduction

CWCB staff members have been actively participating with studies and actions related to the 2002
wildfires experienced in Colorado. Post-wildfire efforts have been ongoing since mid-summer of 2002
with numerous government agencies cooperating to the extent possible. In addition, the Colorado
Department of Natural Resources created a multi-agency response team known as MRRT, chaired by
Kent Holsinger. The MRRT meets approximately every other month to discuss a variety of technical,
administrative, and volunteer issues related to post-wildfire operations. The CWCB chairs the Flood
and Debris Subcommittee for the MRRT.

Of most concern to the CWCB Flood Protection Program is the increased risk to life and property
resulting from post-wildfue flood and debris flow hazards in several bum areas throughout Colorado.
Lessons learned from the 1996 Buffalo Creek fIre and flood events have provided many lessons and
insights regarding increased watershed runoff. The increased flood runoff is caused by destroyed
vegetative cover (both ground and canopy) on the forest hillslopes along with a condition known as
"hydrophobicity" of the soils within the burn area. The hydrophobic soils essentially repel water and
act as an impermeable surface with very little capacity for infiltration. The loss of vegetative cover
reduces the watersheds ability to intercept and absorb the falling precipitation. Depending on bum
severity, geology, topography and other hydrologic factors, the flood runoff from burned watersheds
has been documented to be substantially higher than pre-bum conditions (as much as 20 or 30 times
the pre-bum runoff). Debris flow hazards are greatly increased in those bum areas where latent or
troublesome conditions formerly existed. The Missionary Ridge bum (La Plata County) and the Coal
Seam bum (Garfield County) are examples of where debris flows hazards are of great concern.

In response to the above stated hazards, CWCB and other partners are in the process of producing post-
wildfire flood and debris flow delineation studies that wi\1 be made available to local governments and

Flood Protection. Water Supply Planning and Finance. Stream and Lake Protection
Water Supply Protection. Conservation and Drought Planning