Multi-Hazard Mitigation Plan 4.2 Vulnerability Assessment VULNERABILITY OF THE COUNTY TO CATASTROPHIC DISASTER Once the hazard identification step was complete, the HMPC conducted a vulnerability assessment to describe the impact that each hazard identified in the preceding section would have upon Sacramento County. As a starting point, the HMPC utilized County Assessor data to define a baseline against which all other disaster impacts could be compared. The baseline is the catastrophic, worst-case scenario, the assessed value of the entire county as a whole, $89.5 Billion. The value is deceptively low in that state, federal and other exempt facilities are not included in the county’s assessment, it only reflects commercial and residential property, and Proposition 13 limits property taxes by freezing a property’s assessed value to the value on the date of the most recent sale. The value also does not reflect any infrastructure or other community elements vulnerable to disaster, such as the economic impact to agriculture or business and industry. The figures below represent the value of buildings only. Land values have been purposely excluded because most often land remains following disasters, and subsequent market devaluations are frequently short-term and difficult to quantify. Additionally, state and federal disaster assistance programs generally do not address loss of land or its associated value. TOTAL VALUE, LESS VACANT LAND, AND LAND VALUES FOR IMPROVED PROPERTY CITRUS HEIGHTS 4,647,030,160 ELK GROVE 10,410,394,230 FOLSOM 6,895,628,807 GALT 1,138,391,277 ISLETON 30,232,419 RANCHO CORDOVA 3,828,797,291 SACRAMENTO CITY 28,117,810,904 UNINCORPORATED 34,397,919,841 ===================================== COUNTYWIDE 89,466,204,929 (Source: Sacramento County Assessor's Office, 10-SEP-04, modified by the HMPC) Sacramento County Vulnerability Assessment Multi-Hazard Mitigation Plan Page 4-33 December 2004 In terms of the impact upon the numbers of people, area affected and individual communities, the following table provides a summary of the county exposure to disaster. Sacramento County Land Ownership Population Area (Sq. Mi.) City of Citrus Heights 85,400 14.24 City of Elk Grove 94,850 38.60 City of Folsom 51,300 24.17 City of Galt 19,550 2.95 City of Isleton 840 .46 Rancho Cordova 53,613 33.59 City of Sacramento 411,200 96.34 Unincorporated County 608,687 779.66 County Totals 1,325,440 990.01 Source: County of Sacramento Website, revised by the HMPC Sacramento County Vulnerability Assessment Multi-Hazard Mitigation Plan Page 4-34 December 2004 HOW RISK VARIES BY LOCATION WITHIN THE COUNTY The DMA regulations require that the HMPC evaluate the risks associated with each of the hazards identified through the planning process. For multi-jurisdictional plans, the regulations also require that the risks be further evaluated where a jurisdiction’s risks vary from the risks facing the entire planning area. The hazards identified in Section 4.1 are: • Severe weather • Flood • Dam failure • Earthquakes • Wildfires • Drought • Natural health hazards • Landslides and • Volcanoes The HMPC has determined that the risk for the following hazards differs in some jurisdictions within the county: • Flood (different in every participating community) • Earthquakes (different in Isleton and the other Delta communities) and • Wildfires [different along the American River Parkway (including areas of Fair Oaks Bluff, Carmichael and Folsom]. The HMPC has determined that the risk of the following hazards occurring within the county is minimal or non-existent, as described in Section 4.1, and they are no longer addressed in this plan until such time that information becomes available that changes that assessment: • Landslides and • Volcanoes. VULNERABILITY TO HAZARDS AFFECTING THE COUNTY This section of the plan presents an evaluation of the vulnerability to all hazards that are identified in Section 4.1 as presenting a risk to Sacramento County. Where specific hazard risks vary across the county, a detailed evaluation will be presented in Section 6, The Community Elements. Sacramento County Vulnerability Assessment Multi-Hazard Mitigation Plan Page 4-35 December 2004 SEVERE WEATHER (HEAVY RAINS/STORMS, TORNADOES, FOG) The HMPC addressed severe weather hazards for two reasons: 1. Floods, clearly the hazard posing the greatest and most frequent threat throughout Sacramento County, are almost always a direct result of severe weather. The majority of flooding incidents in the county have occurred between October and March, and are often a result of severe weather associated with storms known locally as the ‘Pineapple Express’. 2. The HMPC research identified frequent occurrences of ‘severe weather’. The HMPC grouped all incidents of hailstorms, thunderstorm winds, tornadoes and fog as severe weather. The State Hazard Mitigation Plan does not identify severe weather as a hazard to be addressed, but it does include the map to the left displaying the number of federal disaster declarations resulting from ‘storms’. The Sacramento County HMPC, having examined the topic, did develop some general recommendations addressing how to reduce the impacts of severe weather. General Statement of Impact upon Sacramento County. Impacts of severe weather, such as ice, snow and windstorms, are usually upon the availability of electric power, as the distribution systems are disrupted through the breaking of power lines. Hailstorms often damage roofs and motor vehicles. Fog results in serious multi- vehicle crashes on Interstates and other major highways. Sacramento County Vulnerability Assessment Multi-Hazard Mitigation Plan Page 4-36 December 2004 ‘Pineapple express’ brings warm air, rain to West. A relatively common weather pattern brings southwest winds to the Pacific Northwest or California, along with warm, moist air. The moisture sometimes produces many days of heavy rain, which can cause extensive flooding. The warm air also can melt the snow pack in the mountains, which further aggravates the flooding potential. In the colder parts of the year, the warm air can be cooled enough to produce heavy, upslope snow as it rises into the higher elevations of the Sierra Nevada or Cascades. Forecasters and others on the West Coast often refer to this warm, moist air as the ‘Pineapple express’ because it comes from around Hawaii where pineapples are grown. Source: USA TODAY research by Chad Palmer http://www.usatoday.com/weather/wpinappl.htm FLOODS River Floods. River flooding is the most significant natural hazard that Sacramento County faces. The Sacramento area has a good working knowledge of the 100-year flood, however, the statistical outlier flood is not as well quantified. Sacramento is not at high risk of flooding but is at low risk of catastrophic flooding. The potential for a flood event is generally between the months of December and March and is exacerbated by heavy snowfall in the mountains and foothills followed by warm rainfall. The Sacramento River extends north to Mount Shasta and the Shasta Reservoir. Many other rivers are tributary to the Sacramento, including (immediately north of Sacramento) the Bear and Feather Rivers. The American River extends to the Sierra Nevada foothills in three branches (South, North and Middle). Folsom Reservoir is at the eastern boundary of Sacramento County and serves to control the American River. The Cosumnes River is a wild and natural river originating in the Sierra Nevada foothills, flowing into southern Sacramento County. This area is mostly rural farmland. Levees were constructed by agricultural interests, and they are inadequate for containing record storm flows such as those experienced in February 1986 and again in January 1997. These two storms left the levee system sorely damaged. Each time, the levee breaks were repaired, but the overall system sits in wait of another flood event. The Mokelumne River is the southernmost river in the County and is controlled by a dam in the neighboring county and levees. All of the watersheds converge at the Sacramento River Delta. The flood issues in the delta are of concern as the agricultural interests continue to farm the land which is subsiding annually, making the levee systems more vulnerable to breaching. More discussion on the Delta is found in the Sacramento County Section of this Plan. Sacramento County Vulnerability Assessment Multi-Hazard Mitigation Plan Page 4-37 December 2004 The American and Sacramento River levees were found to be eroded and there were concerns of substrata seepage. Much of the levee system was decertified and large areas were remapped as flood zone AR in July 1998. Subsequently, there has been much work by SAFCA and the US Army Corps of Engineers to improve the levee system on the American and Sacramento Rivers through the County. It is anticipated that many sections of the levee will be recertified to a 100-year level of protection, in 2005. When the 100-year event is exceeded, the consequences could be catastrophic as flood depths behind levees can range up to many feet deep in some urban areas. It is important that people know that they are protected by these structural flood control systems and purchase flood insurance to protect their financial assets in their homes and businesses. Furthermore, it is important that they are aware of flood warning systems, weather conditions, and river levels and that they have a well rehearsed evacuation plan. There may not be adequate notice to evacuate to higher ground by vehicular travel. Instead, it may be more prudent to find a commercial rooftop or other stable structure to wait out the flood incase the statistically unlikely catastrophic flood event should occur. Stream Flooding. There are many urban streams, channels, canals, and creeks that serve the drainage needs of the County. There is significant threat of flooding in large areas of the county from several of these streams. These watersheds do not know political boundaries. It is important that each community work together to create watershed master plans.