Problem Areas During Emergency Evacuation in South-Eastern Placer County
Author

Name: Gabriele Windgasse
American River College, Geography 350: Data Acquisition in GIS: Spring 2006
Abstract

This termpaper discusses several problem areas that may increase the difficulties during emergency evacuations in south-eastern Placer County.
Introduction

The Oakland Hills Fire in 1991 destroyed or 3000 structures and 25 lives were lost within hours of the fire's start. A number of factors have been identified that significantly contributed to this tragedy:
- the fire started in the "Urban-Wildlife Interface" (UWI)
- the area is heavily populated
- large amounts of fuel were present (plants, structures)
- little water was available to the firefighters
- the physical conditions: steep terrain, narrow, winding and steep roads
- weather conditions (high winds, low humidity).

South-East Placer County has very similar conditions: The UWI along Folsom Lake/American River, the foothills north-east of Lincoln, and the towns in the higher Sierra - all these areas experiencing a dramatic increase in population:
from 1990 - 2000 the population in Placer County increased 43%. From 2000 to 2004 the increase was 23%. More and more people move to the the UWI.
Background

I looked at several aspects that could increase the difficulties during emergency evacuations. Steepness of hills (difficulty of emergency vehicles accessing area); aspects of hills (facing the canyons/willife areas); presence of only one egress route ("cul de sacs").
Methodology

Data layers used:
Topographic map of California; Tiger Line File for roads in Placer County; DEM for cul-de-sacs, hillshades, aspects and steepness of roads; NAIP 1m resolution aerial photo of Placer County (2005) as base layer; GPS locations near UWI; photos of UWI, linked to map (GPS-Photo-Link software).

The GPS unit (Garmin GPS 76) was coordinated with the clock in the digital camera (HP), and the GPS-Photo-Link Software (www.geospatialexperts.com) was used to link the waypoints to the photos taken.
The CASIL webpage was the source for the Tiger Line files (roads layer) and the DEM. Contour analysis was done using the ArcMap GeoSpatial Analyst Extension. The steepness of slopes was classified so one can recognize steep (30 - 60 m/100 m) and very steep (> 60 m/100 m) slopes.
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No tool in ArcMap could be found tht would identify "cul-de-sacs", so I selected a number of recognizable and known dead-end roads in the UWI near Auburn-Folsom Road and Horseshoebar Road. As a background layer, a very recent aerial photo (1m resolution) of Placer County was used (NAIP)
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Analysis
I encountered several problems: I could not convert the classified slope-steepness into a layer file. I would like to have used this layer to select all roads that were steep or very steep. All data layers used the Teale-Albers Projection (NAD 27). Only the NAIP aerial photo was in a different projection (UTM, NAD 83). I tried several times to re-project the raster image using the ArcMap tool (project raster) - each re-projection took more than 1 hour and terminated before the reprojection was complete. The off-set between the road-layer and the raster image varies: up to 300 ft. I used the GPS-Photo-Link to mark the waypoints for several photos of the UWI.
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Conclusions
Several conditions were investigated that could impede access and egress during an emergency evacuation in South East Placer County: proximity to the UWI, steep roads and presence of cul-de-sacs. GIS analysis could be done for some, but not all of the investigated parameters. The combination of these three factors (UWI, steepness of terrain and cul-de-sac) should be considered when planing for emergency evacuations.
Additional information could be added, to make these maps more applicable: population data (density, age distribution, age of housing); type of roads (one lane, dirt road,....), flood information (100 year and 500 year flood plain); boundaries of the adjacent Fire Protection districts.

References

sources and links indicated in text