Ada County Hazard Vulnerability Analysis 2010 Ada County Hazard Vulnerability Analysis March 2010 2 Table of Contents INTRODUCTION .......................................................................................................................... 5 DAM FAILURE ............................................................................................................................. 9 DROUGHT ................................................................................................................................... 17 EARTHQUAKE ........................................................................................................................... 19 FLOOD ......................................................................................................................................... 27 HAZARDOUS MATERIALS ...................................................................................................... 47 HEALTH....................................................................................................................................... 51 Seasonal influenza .................................................................................................................... 51 Pandemic Influenza ................................................................................................................... 51 Avian Influenza ......................................................................................................................... 51 SARS......................................................................................................................................... 51 West Nile Virus......................................................................................................................... 51 Radon ........................................................................................................................................ 52 LANDSLIDE ................................................................................................................................ 55 MORMON CRICKETS ................................................................................................................ 59 NUCLEAR WAR ......................................................................................................................... 61 STRUCTURAL FIRE ................................................................................................................... 67 TERRORISM ................................................................................................................................ 73 TRANSPORTATION ................................................................................................................... 81 UTILITY FAILURE ..................................................................................................................... 87 VOLCANO ................................................................................................................................... 93 WEATHER ................................................................................................................................... 99 Thunderstorm ............................................................................................................................ 99 Lightning ................................................................................................................................... 99 Wind ........................................................................................................................................ 100 Hail .......................................................................................................................................... 100 Flash Floods / Floods .............................................................................................................. 100 Tornadoes ................................................................................................................................ 100 Winter Storms ......................................................................................................................... 101 Extreme Heat .......................................................................................................................... 101 WILDFIRE ................................................................................................................................. 107 HAZARD VULNERABILITY & RISK ASSESSMENT TOOL .............................................. 114 Ada County Hazard Vulnerability Analysis March 2010 3 Ada County Hazard Vulnerability Analysis March 2010 4 INTRODUCTION In order to plan for emergencies which might strike Ada County it is necessary to identify and understand the hazards that potentially could impact it. Only by understanding the hazards and their impacts is it possible to adequately mitigate, plan for, respond to, and recover from them. Therefore this Hazard Analysis serves as a basis for the development of plans, public education programs, responder training, and disaster exercises. Although this analysis does not cover all hazards, it does address those believed to have a reasonable potential for impacting the people, property, economy and environment of Ada County. Ada County Profile Ada County is located in the southwestern part of the State of Idaho. The area was originally inhabited by Native Americans. British fur trappers were the first explorers on record to enter the Boise Valley. The old Oregon Trail, based upon trails created by nomadic Native Americans passes through the county. In 1862 gold was discovered in the Boise Basin. On March 4, 1863, the United States Congress established the Territory of Idaho. In July 1863 the US Army built Fort Boise on what is now the northeast part of Boise City. The Idaho Territorial Legislature created Ada County on December 22, 1864. The county is named for Ada Riggs; the first pioneer child born in the area. In 1869 the territorial prison was built. There are six incorporated cities in Ada County: Boise, Eagle, Garden City, Kuna, Meridian, and Star. The City of Boise is the county seat, as well as the capital of the State of Idaho. In 2009 the population of Ada County was estimated to be just over 400,000 people. This represents nearly 25% of the state’s population. Geography and Climate The county is approximately 1,060 square miles is size. Roughly half of this is public land, while the other half is privately owned. The county includes many acres of grassland/sagebrush and a small amount of timbered lands. Terrain ranges from 5,750 feet in elevation in the northern mountains, to 2,260 feet elevation along the broad southern floodplains. Elevation in Boise ranges from 2500 feet to 2850 feet. Elevation in the City of Star, at the western end of the county is about 2,470 feet. The Snake River forms part of the county’s southern boundary. The southern half of the county is largely undeveloped, as it is mostly federal land. The Boise River flows through the county from east to west and eventually drains into the Snake River. The Cascade and Blue Mountain Ranges in Oregon and Washington modify Pacific air masses as they move east to the Treasure Valley. The result is that these air masses are considerably drier once they reach Southwest Idaho. In addition, the Rocky Mountains to the east act as a barrier to cold shallow air masses moving southward from Canada in winter. The effect from all these Mountain ranges is to make Ada County semi-arid with relatively mild winters for its northern location. Native vegetation consists primarily of sagebrush, sparse desert grasses and other Ada County Hazard Vulnerability Analysis March 2010 5 Great Basin Flora. A large variety of native and non-native trees thrive in the Boise River Basin. Agricultural land in Ada County is heavily dependent on irrigation, with this moisture playing a role in modifying the local climate to some extent. During most winters periods of stormy and mild weather alternate. Most summers are dominated by a typical upland continental climate, with rainfall confined to occasional afternoon or evening thundershowers. Maximum temperatures of 100 degrees or higher occur nearly every summer. Annual precipitation ranges from about ten inches in the southwest to twenty-plus inches in the foothills north and east of Boise. Boise City averages about 12 inches of precipitation a year. Transportation Principal transportation routes are Interstate 84 and US Highways 20, 26, 30, which all traverse the county along the same four lane highway from southeast to northwest. Idaho State Highway 44 is a two-lane route that parallels I-84 from Boise to its connection with I-84 in Canyon County. Idaho State Highway 16 provides access north to Emmett and State Highway 55 provides access north to Horseshoe Bend and Valley County. Idaho Highway 21 provides access to the central mountains via Idaho City and Stanley. Ada County Hazard Vulnerability Analysis March 2010 6 Definitions Hazard – is a dangerous event or circumstance that has the potential to lead to an emergency or disaster. Vulnerability – is the susceptibility of life, property, or the environment to damage if a hazard occurs. Risk – is the probability of suffering those damages. For hazards in this document risk will be assigned as one of four levels: • very low • low • medium • high Websites: http://www.adaweb.net/ http://idaho.gov/aboutidaho/county/ada.html http://www.accem.org Ada County Hazard Vulnerability Analysis March