FLOOD04102

• County: Jefferson
• County: Park
• Community: Buffalo Creek
• Basin: South Platte
• Title: Buffalo Creek Hydrology and Mitigation Summary
• Date: 9/4/1996
• Prepared For: Jefferson County
• Floodplain - Doc Type: Flood Mitigation/Flood Warning/Watershed Restoration

Environmmtal and Enaineerinr Geology of the Wuatch aom RqiDn
Utah Geolop.l Aaociatim. PublicItion 24, 1995
William R. Lund. editor
G,I,S, APPLICATIONS IN mE NORTHERN WASATCH FRONT
PRE-FIRE HAZARD RISK ASSESSMENT
DA VIS AND WEBER COUNTIES, UTAH
NORMAN C. EVENSTAD AND ROBERT C. RASEL yl
ABSTRACT

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Communities are encroaching rapidly along the base of the steeply rising Wasatch Mountains
because of the high quality views found there. The increased growth has signiticantly increased the
risk of wildtire damage. This study includes the cities between North Salt Lake and Pleasant View,
Davis and Weber Counties, Utah.
Wildfires are only the initial hazard. Fire makes the burned areas susceptible to hazards from the
next intense stonn flow. The resultant excessive sediment delivery represents a signiticant hazard to
downstream urban areas. The main objective of this study was to provide quick access to quantitative
post-tire sediment delivery data for cities and counties. This will facilitate a rapid response in post-tire
emergency mitigation action. Previously, these assessments took from two to ten days to complete.
Geographic Infonnation System layers were developed to deliver this procedure to city and county
planners and emergency response staffs. Sediment yield rates were developed for each individual
canyon-fan drainage way and the interfluve areas for the before-fire, post-fire low intensity burn and
post-tire high intensity burn conditions. The layers of infonnation developed for this study include
sediment yield, slope failure, vegetation, soil, slope and watershed sub-basins. These GIS databases
can be updated in the future and can also be manipulated for more detailed analysis of natural
resources or hazards,
Sponsorship for the project came from cities, towns, counties, and the State of Utah, Division of
Comprehensive Emergency Management. Funding for the study was developed through the River
Basin Program of the United States Department of Agriculture, Natural Resources Conservation
Service.
The use of a Geographic Infonnation System in this assessment will save critical reaction time
during the post,tirehazard mitigation assessments. Damage potential was based on sediment yield
volurne and a risk assessment rating of low, medium or high was developed.

INTRODUCTION

The escalating development of communities along the
western slopes of the Wasatch Mountain range has become
an increasingly important issue to city, county, state, and
federal officials concerned with public safety and land
management. A major portion of Utah's population lives '
along the Wasatch Front corridor. Davis and Weber counties
account for 20 percent of the state's population on I percent
of Utah's surface area. This represents a signiticant
population affected by land management policies developed
for the urban-wildland interface and National Forest System
Land. Some of the biggest hazards confronting landowners
along this corridor involve debris flows, debris floods, debris
slides, and wildland tires, These hazards not only affect
people living in the urban-wildland interface, but also people
living along the many drainage corridors further downstream
of the canyon outlets.
Wild fires along the Wasatch Front pose a two fold
threat to landowners. There is the obvious fire hazard and
then a flood and debris hazard from storm events that impact
the burned watershed. A steep area impacted by a wildtire
can create a "loaded-gun" situation if a rainstonn occurs
before vegetation can re.establish. This set of circumstances
became reality with the Affleck Park Fire (September 19BB)
located east of Salt Lake City in Emigration Canyon. In this
case, emergency measures to collect debris and sediment in
the upper watershed prevented heavy damage to houses
downstream. However, precious time was lost because
sediment yield modeling had to be penonned before an
informed decision could be made on the extent of needed
emergency watershed protection. The infonnation developed
from this study will allow for a more rapid response in the
development of an emergency watershed protection plan

in the event of a watershed degrading wildfire along the
Wasatch Front.

LOCATION

The study area encompasses the western front of the
Wasatch Range in Davis and Weber counties. It contains
about 63,000 acres of steep, rugged terrain with alluvial fans
and steep, contined drainage channels. The area is subject to
intense summer thunder stonns that produce flash floods and
a heavy snowpack which can create periods of high runoff
during the spring thaw. The western extent of the study area
tenninates approximately along the boundary of the ancient
Lake Bonneville shoreline at an elevation of about 5,200 feet
(Figure I). See Map-\ for more detail.

UTAH

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Figure 1. General Location Map, northern Wasatch Range,
Davis and Weber counties, Utah.

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