THE ALLEN RESIDENCE, A MOUNTAIN DREAM HOME
DESTROYED BY AVALANCHES - AN EXAMPLE OF
POOR LAND-USE PLANNING, SUNDANCE, UTAH

by Richard Giraud

ABSTRACT

Investigation into a residence destroyed by avalanches provides an excellent example of poor avalanche hazard land-use planning. The Allen residence was a mountain dream home constructed in an avalanche runout zone near the Sundance Ski Resort, Utah. A chronology of events pertaining to the Allen residence was used to investigate residential development of an avalanche runout zone and the resulting economic loss. Structural damage and economic loss could have been prevented if adequate land-use planning and engineering guidelines were followed.

On February 13, 1986, the residence was struck by an avalanche which substantially damaged the structure. A law suit, Transamerica Insurance Company v. Sundance Development Corporation and others was filed and eventually dismissed without a conclusive ruling. On February 25, 1993, the residence was struck by a second avalanche destroying the remaining structure and damaging adjacent homes. Mapping of vegetation patterns and avalanche terrain could have provided design information for avalanche magnitude, frequency and runout behavior. Mitigation of the avalanche hazard is critical to avoid additional damage to adjacent homes and possible loss of life. Hazard mitigation could include both operational and structural methods.

INTRODUCTION

The Allen residence was a private home that was struck by two snow avalanches. This paper presents a chronology of events regarding the Allen residence, avalanche hazard evaluation techniques to define the hazard and mitigation possibilities for remaining homes exposed to the avalanche hazard. The Allen residence is located in the Wasatch Mountain Range ten miles east of Orem, Utah. The Allen residence is part of the Sundance Mountain Home Development which is northwest of the Sundance Ski Resort.

Two other homes are located adjacent to the Allen home, one uphill and one downhill. The homes are located in the runout of the Bearclaw (sic) avalanche path. Several avalanche paths are present west and southwest of the site. U. S. Forest Service land is present west of the site and is part of the Mt. Timpanogos Wilderness Area. The homes have a spectacular view of Cascade Cirque and the Stewarts Cascades (waterfalls) on the east side of Mt. Timpanogos. The view includes nearly 5,000 vertical feet of relief.

When the residence was struck by the first avalanche it was owned by Robert Allen. For the purposes of this paper the residence or destroyed residence is referred to as the Allen residence. Locally the site is known as the Allen house.

METHODS

Several sources were utilized to construct the chronology of the Allen residence. Utah County planning files provided information on the building permit, plat maps of the development, and the protective covenant for the development. Utah County assessor records were used to document the property value through time. U. S. District Court records were useful in obtaining a consulting report of the 1986 avalanche damage and court decisions. The Daily Herald was used to gain newspaper information concerning avalanche dates and damage. Utah Avalanche Forecast Center (UAFC) avalanche advisories are used to profile the forecasted backcountry avalanche hazard.

Field visits were used to observe terrain, avalanche path aspect, age density and types of vegetation, vegetative growth patterns, and character of damaged vegetation. Slope angles used in this report were measured on profiles constructed from the U. S. Geological Survey 7.5 minute Aspen Grove quadrangle and directly from slopes in the field.

HISTORICAL BACKGROUND AND PREVIOUS WORK

Snow avalanches have always conflicted with human development in the Wasatch Mountains. Historical usage of the Wasatch Mountains has shifted from mining to winter recreation and development. Likewise, the avalanche hazard has shifted from mining to winter recreation and development.

In describing avalanches along the Wasatch Front, Perla (1971) points out that a growth in winter usage and development has increased public exposure to avalanche hazard. Perla provides examples of evaluating sites based on terrain and vegetation when planning new construction. Perla also lists avalanches that have caused property damage in Provo Canyon.

Christian (1986), in a Daily Herald newspaper article describes avalanches at Bridal Veil Falls in Provo Canyon. Large avalanches occurred at Bridal Veil Falls during March 1924, February 1932 and February 1986. Bridal Veil Falls is approximately three miles south of the development.

DESCRIPTION OF DAMAGING AVALANCHES

February 13, 1986 Avalanche

The February 13, 1986 avalanche damage to the Allen residence is described in a consulting report by Karren and Associates (1986). The avalanche struck at 3:37 PM when no one was in the home. The rear (southern) windows, walls and sky lights were broken. The snow flowed around, over and through the home and continued downhill until it was stopped in part by the residence below the Allen home (Figure 1). The snow depth at the rear wall was 20 feet one week after the slide. A Utah County building inspector posted the wrecked structure as a public hazard and placed off-limit signs at the building (Christian, 1986). Furniture and personal belongings were swept out of the home and strewn along the front of the lot. The consulting report mentioned that the house was repairable but extensive work is required and the home must not be repaired and occupied until an avalanche defense structure is built.

Figure 1. The Allen residence after the February 13, 1986
avalanche.  View looking southwest.  Photo by Pat Christian
for The Daily Herald (2-16-86).

The avalanche path is an uncontrolled hazard and representative of backcountry avalanche conditions. The backcountry avalanche forecast issued by the UAFC is used to profile the avalanche hazard at the time of the slide. The UAFC issued an avalanche warning on the morning of February 13, 1986 for the northern Wasatch Mountains from the Utah-Idaho border to Spanish Fork Canyon, which includes the Provo area mountains (UAFC, 1986). Fourteen to thirty three inches of high density new snow was reported throughout the mountains. The backcountry avalanche hazard was reported as extreme with large destructive avalanches certain. The forecast advised staying well away from large avalanche runout zones. The avalanche warning remained in effect through February 22, 1986.

February 25, 1993 Avalanche

The Allen residence was struck by a second avalanche on February 25, 1993 destroying all of the structure except the concrete towers and foundation. House debris were scattered down the hillside north of the home (Figures 2 and 3). The Allen residence had been abandoned since the 1986 avalanche. The homes uphill and downhill of the Allen residence also suffered significant damage (Daily Herald, 1993). There were no injuries reported with the avalanche. The February 25, 1993 slide was larger than the February 13, 1986 slide both in runout distance and property damage.

The UAFC backcountry avalanche forecast for February 25, 1993 was for a high hazard at upper elevations exposed to wind and that natural avalanches were occurring on slopes of all aspects 35 degrees and steeper (UAFC, 1993). Later in the day on February 25, 1993 after more snow had fallen, the hazard was forecasted as high on slopes 30 degrees and steeper and elevations above 6,500 feet.

Both avalanches were part of major avalanches cycles affecting the Wasatch Mountains. The February, 1986 cycle was a longer cycle, however, both cycles caused significant property damage and loss of human life in the Wasatch Mountains.

UTAH COUNTY PLANNING AND ASSESSOR RECORDS

Planning Records

Utah County planning records were reviewed to obtain background information on the Allen residence and the Sundance Mountain Home Development. A protective covenant for the Sundance Mountain Home Development was drafted to protect the natural beauty, view and surroundings of the development. The area northwest of the Allen residence is designated as an open area by the covenant. The open area, is in part, composed of avalanche runout zones and lacks view obstructing vegetation. The open area was likely designated to maintain unobstructed views of Cascade Cirque and Stewart Cascades. The building permit for the home was approved on September 9, 1983.

Figure 2. The avalanche runout zone after the February
25, 1993 avalanche. Note pieces of house debris scattered
down the runout. View looking north (2-26-93). Photo by
Rand Decker.



Figure 3. View looking up the runout zone with the Allen
house (concrete tower) visible in the background. Note
pieces of house debris in the foreground. View looking
south (5-8-94).

Assessor Records

County assessor records were reviewed to track the value of the home before and after it was struck by avalanches. The property class is listed as secondary residential, built in 1984 as a single family structure with a floor area of 7,322 square feet. The Allen residence (structure and land) was accessed in 1985 at a market value of $836,369. Christian (1986) reports the value of the house at a million dollars plus. This discrepancy may be due to the value of real property (structure and land) plus the personal property inside the structure. After the February 13, 1986 avalanche the property was accessed at $582,882. The property declined in value to $303,652 prior to the February 25, 1993 avalanche. The 1993 accessed market value after the February 25, 1993 avalanche was $105,132.

U. S. DISTRICT COURT RECORDS

A law suit resulted from the February 13, 1986 avalanche. The suit was filed in the U. S. District Court, District of Utah, Central Division in Salt Lake City. The case, Transamerica Insurance Company v. Sundance Development Corporation and others was filed in 1987 (Case No. 87C-0921S). A court order on November 8, 1989 dismissed the case and stated that each party bear its own costs.

ALLEN RESIDENCE SUMMARY CHRONOLOGY

The following is a summarized chronology of the Allen residence.

-September 2, 1983 the building permit is approved.

-The accessed 1985 market value of the property is $836,369.

-February 13, 1986 the home is struck by an avalanche. No one was in the home at the time of the slide. Damage was extensive.

-Accessed 1986 market value of the property after the February 13, 1986 avalanche is $582,882.

-The law suit Transamerica Insurance Company v. Sundance Development Corporation and others was filed in 1987.

-November 8, 1989 the court case is dismissed, each party was ordered to bear it's own costs.

-The accessed value of the property before the February 25, 1993 avalanche is $303,652.

-February 25, 1993 the structure is struck by a second and larger avalanche. The homes above and below the Allen residence are also damaged.

-After the February 25, 1993 avalanche the 1993 accessed property value is $105,132.

GEOMORPHOLOGY AND VEGETATION MAPPING

The Bearclaw Cabin avalanche path is a steep northeast facing gully directly above and southwest of the Sundance Mountain Home development. The Allen residence is adjacent to steep mountainous terrain on a north facing slope at an approximate elevation of 6,700 feet. The avalanches travel approximately 1,900 feet vertica1 and 3,300 feet horizontal to reach the Allen residence. The slope angles of the avalanche starting zone and track are 37 degrees. Avalanche flow is confined in the starting zone and track by a gully. Avalanche flow is unconfined in the runout zone. The runout slope angle in the vicinity of the Allen residence is 17 degrees. Historical avalanche behavior has demonstrated that the runout slope angle is too steep for moderate and large avalanches to decelerate and stop before impacting the Allen residence.

Surrounding mountain slopes have forests of conifer and aspen trees. Scattered conifers, aspen and small shrubs are present near the Allen residence. Mature conifer trees are present outside of active avalanche paths. Burrows and Burrows (1976), mention that shrubs are often useful indicators of the frequency of avalanching or intensity of disturbance because they can grow in sites where trees cannot survive. Frequent avalanching keeps the vegetation in the starting zone and track to a minimum. Frequent avalanching also has resulted in small trees and shrubs in the runout zone.

The vegetation trim lines in the avalanche runout are both sharp and ragged. The trim lines suggest different avalanche flow patterns in the runout. Many of the conifer trees near the Allen residence and adjacent homes are missing the uphill branches. The apparently avalanche damaged conifer trees and shrubs near the homes suggests that avalanches runout into the developed home area.

AVALANCHE HAZARD PLANNING, EXISTING HAZARD AND MITIGATION

Avalanche Hazard Planning

The avalanche hazard, at the development, was either ignored or not recognized. The avalanche hazard was not considered in the planning, designing or developing of homes constructed in the runout zone. This has resulted in the Allen residence being destroyed and the two adjacent homes being damaged. Utah County has a natural hazard ordinance but the ordinance does not include avalanches. An avalanche ordinance, if properly enforced, could be used as a zoning

tool to avoid areas where the risk is unacceptable and to properly design structures to reduce the risk presented by avalanches.

A study of the avalanche hazard would have provided planning and development guidance. The hazard and associated risks could be quantified objectively. The frequency and magnitude of avalanches impacting the site could have been estimated. Avalanche runout distances, velocity and impact pressure could be estimated and used in the design and location of homes.

Existing Avalanche Hazard

The avalanche path has the terrain, climate and snowpack to produce large destructive avalanches. Homes adjacent to the Allen residence continue to be exposed to the avalanche hazard. Keaton (1988) lists five responses to natural hazards: continue current practice, modify the hazard, modify what is at risk, modify procedural and/or operational aspects, or avoid the hazard. Avoiding the hazard is not possible since the residences already occupy an avalanche runout zone. The avalanche hazard could be modified, what is at risk could be modified and procedural and/or operational aspects could be modified.

Avalanche Hazard Mitigation

Avalanche mitigation methods are used to eliminate or reduce the hazard to an acceptable level. Mitigation of avalanche hazard is generally more feasible and effective when proposed structures are concerned rather than existing structures. The reduction of risk by zoning and design is not possible because the homes are already constructed. Likewise, the hazard cannot be eliminated. An acceptable level of risk would need to be determined and then mitigation alternatives could be evaluated to determine hazard reduction and cost feasibility.

Even though the mitigation possibilities are limited because the homes are constructed, structural and operational mitigation methods should be evaluated. Structural mitigation methods could involve the construction of arresting, deflecting or catchment structures in the runout zone. Supporting structures in the starting zone would not be possible because the starting zone is in the Mt. Timpanogos Wilderness Area where permanent manmade structures are not allowed.

Operational mitigation methods could consist of seasonal occupation, occupation with an evacuation alternative and explosive control of avalanches. Seasonal occupation would involve usage when the avalanche hazard is not present, generally May through October. Occupation with an evacuation alternative could be used to reside in the homes during the winter months. Evacuation would be based on avalanche hazard forecasting. Seasonal occupation and occupation with an evacuation alternative only protects human life and not damage to structures. Artificial release of avalanches by explosives is a widely used form of mitigation for ski areas and highways. Artificial release generally involves the release of smaller avalanches to limit the release of large avalanches.

DISCUSSION

Snow avalanches have conflicted with human habitation in the Wasatch Mountains since the area was first settled in the mining era of the late 1800's. The Allen residence was constructed in an avalanche runout zone and was destroyed by avalanches. The adjacent homes remain exposed to the hazard. The property damage and economic loss may have been avoided if adequate land use planning would have been followed. A study of the hazard could have provided planning and development guidance.

Based on recent history and vegetation patterns, avalanches will continue to impact the homes adjacent to the Allen residence. The Allen house and adjacent homes were constructed without any regard to the avalanche hazard. Mitigation possibilities are limited because of this. Different mitigation methods should be evaluated to determine hazard reduction, mitigation effectiveness and cost feasibility.

Avalanches are a normal process of nature. Nature cannot be fooled and the future will always come. Avalanches will continue to run into the developed home area. If the hazard is not mitigated, additional property damage will result and human lives may be lost. As the philosopher George Santayana said: "Those who fail to remember the past are condemned to repeat it".

ACKNOWLEDGEMENTS

I would like to thank Rand Decker for his suggestion of the problem, his discussion and use of photographs. Bruce Tremper was very helpful in supplying avalanche forecast and weather data. Darce Trotter was helpful to focus the project.

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