Table of Contents. Section 3: Hazard Identification and Risk Assessment

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1 Table of Contents Introduction Hazard Identification Previous State Plans Disasters and Emergencies in Colorado State Declarations Federal Declarations Insured Losses Local Mitigation Plans Hazard Profiles Atmospheric Hazards Drought Extreme Heat Floods Hailstorms Lightning Precipitation Thunderstorms Tornadoes Windstorms Winter Weather Geologic Hazards Avalanche Earthquake Erosion and Deposition Expansive Soils Landslides, Mud and Debris Flow, and Rockfalls Subsidence Other Fire Grasshopper Infestation Vulnerability State Asset Exposure Local Jurisdictions Future Development Potential Losses State Asset Losses Local Jurisdictions Future Development Colorado Natural Hazards Mitigation Plan 3 1

2 Consequence Analysis Avalanche Drought Earthquake Erosion and Deposition Expansive Soils Fire Flood Grasshopper Infestation Hailstorms Landslides, Mud and Debris Flow, and Rockfalls Lightning Precipitation Subsidence Summertime: Extreme Heat Thunderstorms Tornado Windstorms Winter Weather Colorado Natural Hazards Mitigation Plan 3 2

3 RISK ASSESSMENT: 201.4(c)(2): [The State plan must include a risk assessment] that provides the factual basis for activities proposed in the strategy portion of the mitigation plan. Statewide risk assessments must characterize and analyze natural hazards and risks to provide a statewide overview. This overview will allow the State to compare potential losses throughout the State and to determine their priorities for implementing mitigation measures under the strategy, and to prioritize jurisdictions for receiving technical and financial support in developing more detailed local risk and vulnerability assessments. Introduction The purpose of the Hazard Identification and Risk Assessment (HIRA) is to identify natural hazards and to evaluate the risk to the State of Colorado, the health and safety of its citizens, property, and economy. A vulnerability and risk assessment is a decision support tool for determining the need for and prioritization of mitigation measures to protect assets and processes. While it is financially unfeasible to reduce risk from every natural hazard event, vulnerability and risk assessments can help ensure that the available resources and actions taken are justified and implemented based on the threat, vulnerability, and risk. Hazard identification and the assessment of associated risks is a shared responsibility between the state and local communities. Both the state and local communities assess the risks from hazards as part of their respective planning processes. While local governments focus on the hazards, vulnerabilities, and risks on a local or regional scale, the state focus remains on the regional and statewide implications of hazards. The HIRA is divided into the following sections, providing a detailed discussion of process, approach, and content: Introduction Hazard Identification Hazard Profiles Vulnerability Loss Estimates Consequence Analysis Colorado Natural Hazards Mitigation Plan 3 3

4 Hazard Identification Requirement 201.4(c)(2)(i): [The State risk assessment shall include an] overview of the type of all natural hazards that can affect the State. This section identifies the hazards that are probable, or based on future probability, likely to negatively impact the State of Colorado. The primary methods of determining which hazards to include in the 2010 State Plan update included the evaluations of: Previous State Plans Disasters and Emergencies in Colorado Insured Losses Local Mitigation Plans Review and analysis by the SHMT revealed the list of hazards from the 2004 plan remained relevant for the 2007 plan, as well as the 2010 plan update. In addition to hazards identified in previous planning processes, grasshopper infestation was included in the 2010 plan. Grasshopper infestation was added because it has previously been declared as a state disaster and it is called out in state legislation (SB 92-36). The natural hazards identified for Colorado and used for this risk assessment are: Avalanche Drought Earthquake Erosion and Deposition Expansive Soils Wildfire Floods Grasshopper Infestation Hailstorms Landslides, Mud/Debris Flows, Rockfalls Lightning Precipitation Subsidence Summertime: Extreme Heat Thunderstorms Tornadoes Windstorms Winter Weather Previous State Plans The 2004 State Hazard Mitigation Team (SHMT) reviewed all the natural hazards that FEMA has identified (FEMA publication 386-2, Understanding Your Risks: Identifying Hazards and Estimating Losses 2002) and determined which were of concern in Colorado. Coastal related hazards (costal erosion, costal storm, hurricane, and tsunami) and volcanoes were eliminated for consideration because of unlikely impact on the state. Dam failure is incorporated into the flood annex and is not addressed in this hazard identification. Colorado Natural Hazards Mitigation Plan 3 4

5 Disasters and Emergencies in Colorado Historic state and federal-level disaster or emergency declarations were reviewed to ensure coverage of events in the State Plan. These state and federal declarations are listed in the tables below as a consolidated set of data rather than including in each hazard profile section. State Declarations Colorado disasters and emergencies declared by the Governors from 1980 to early 2010 are shown in Table 3-1. Note the diversity in types of events declared: grasshopper infestation, drought, wildfires, tornadoes, rockfalls, floods, sinkholes, mudslides, and blizzards. Table 3 1: Disasters in Colorado, 1980 to 2010 Year Hazard Location 2010 Wildfire Larimer County 2010 Wildfire Boulder County 2010 Rockslide I Severe Blizzard Statewide 2009 Severe Spring Snowstorm Statewide 2008 Wildfires Crowley County 2008 Contamination of Water Supply Alamosa 2008 Severe Tornadoes in Northern CO Weld and Larimer Counties 2008 Fire Housetop Fire, Mesa County 2008 Wildfires Las Animas County 2007 Tornado Holly, Prowers County 2007 Tornadoes Prowers, Phillips, Cheyenne Counties 2007 Rockfalls I 70, US 6 Garfield, Clear Creek, Jefferson 2006 Snow Emergencies 2 Executive Orders December 24 counties 2006 Severe Winter Storm October Southern Colorado, including El Paso County 2006 Wildfires multiple Executive Orders Garfield, Teller, and Custer Counties 2006 Wildfire 2 Executive Orders Las Animas and Huerfano Counties, Costilla and Huerfano 2006 Drought South Platte Basin in Northern Colorado 2006 Flooding Douglas, Teller, Fremont, Pueblo, Garfield Counties 2005 Wildfire Pueblo and Custer Counties 2004 Wildfire Larimer County 2004 Tornadoes Logan County 2003 Sinkhole Interstate 70, Eagle County 2003 Wildfire Cherokee Fire 2003 Snow Emergency Statewide 2002 Wildfires Statewide 2002 Mudslides San Miguel County 2002 Drought All counties 2001 Severe Winter Storms Eastern Plains and Front Range counties Colorado Natural Hazards Mitigation Plan 3 5

6 Year Hazard Location 2000 Flood Elbert County 2000 Wildfires multiple Executive Orders Jefferson, Park, Boulder, Larimer, Las Animas 1999 Flood 2 Executive Orders Sedgwick County, Washington County 1999 Flooding, Landslides, Mudslides Bent, Crowley, Custer, El Paso, Elbert, Fremont, Kiowa, Larimer, Otero, Las Animas, Pueblo, Weld 1998 Landslides, Rockfalls Archuleta, Garfield, Mesa, Gunnison, Rio Blanco 1998 Wildfire Mt. Evans 1997 Blizzard 2 EOs in October, December South Central Colorado, Front Range East 1997 Landslides Jefferson County 1997 Flooding Fort Collins, Weld, Morgan, Logan, Phillips, Clear Creek, Elbert, Kiowa, Baca, Otero, Lincoln, Crowley, Prowers, Sedgwick County, Holyoke 1996 Tornadoes Morgan and Washington Counties 1996 Fire Buffalo Creek, Jefferson County 1996 Flood Buffalo Creek, Jefferson County 1996 Wildfire, Drought, Severe Weather Several Locations 1995 Flood Weld, Morgan Counties 1994 Flood Pueblo County, Lyons Boulder County 1994 Wildfires Garfield, Delta, Douglas, Jefferson, statewide 1992 Flood Fort Collins 1990 Hailstorm Denver, Boulder 1990 Wildfire Olde Stage Fire, Boulder County 1990 Severe Thunderstorm El Paso 1990 Tornado Limon 1990 Blizzard Several Locations 1989 Wildfire Black Tiger Fire, Boulder County 1989 Flooding Town of Rico 1988 Wildfire 3 Executive Orders Lefthand Canyon, Boulder County, Larimer County, Fremont 1988 Tornado Denver 1987 Wildfire Garfield 1987 Flood Mitigation Alamosa 1987 Wildfire Cheyenne, Lincoln, Elbert 1987 Flooding Park 1986 Earth Slide Delta 1986 Earthflow SH 133, N of Paonia Res Winter Storm Weld 1984 Severe Winter Storm Conejos County 1984 Water System Oak Creek, Routt County 1984 Flooding Delta, Dolores, Hinsdale, Saguache, Mesa, Montrose, Moffat, Rio Blanco, Pitkin, San Miguel, Ouray, Eagle, Gunnison, and Silt 1982 Severe Winter Storm Denver, Arapahoe, Adams, Jefferson, Boulder, El Paso, Weld 1982 Dam Failure Lawn Lake Dam, Larimer 1982 Flooding Ouray County 1981 Water System City of Trinidad and Vicinity 1981 Grasshopper Infestation Eastern Colorado Counties 1981 Dam Safety Adams, Weld 1981 Tornadoes Adams, Denver, Jefferson, Weld Colorado Natural Hazards Mitigation Plan 3 6

7 Year Hazard Location 1980 Grasshopper Infestation Logan, Morgan, Sedgwick, Phillips, Washington, Weld 1980 Flooding Weld, Logan, Washington, Morgan, Larimer, Sedgwick 1980 Severe Winter Storm Cheyenne, Kit Carson Federal Declarations Source: Colorado Division of Information Technology State Archives 2007 website Colorado has received seven presidential disaster declarations and three emergency declarations for events from 1980 through December 2009 as shown in Table 1-#. For the four recent presidential disasters and three emergency declarations since 1997, Colorado was awarded dollar amounts for Public Assistance (PA), Individual Assistance (IA), and the Hazard Mitigation Grant Program (HMGP) as shown in Table 3-2. Table 3 2: Presidential Disaster and Emergency Declarations, 1980 to 2009 Year Disaster Number Disaster Event Description 1982 DR 665 CO Estes Park Dam Break Flood 1984 DR 719 CO Western Slope Flooding 1997 DR 1186 CO Flood Disaster in Colorado 1999 DR 1276 CO Severe Storms, Flooding, Landslides and Mudslides 2001 DR 1374 CO Severe Winter Storms 2002 DR 1421 CO Wildfires Assistance Program Public Assistance Individual Assistance Hazard Mitigation Public Assistance Individual Assistance Hazard Mitigation Public Assistance Hazard Mitigation Individual Assistance Hazard Mitigation Federal ( Millions) Unknown EM 3185 CO Snow Emergency Public Assistance EM 3270 CO Snow Emergency 2006 EM 3271 CO Snow Emergency 2008 DR 1276 CO Severe Storms and Tornadoes Public Assistance 11.0 Individual Assistance Hazard Mitigation In addition to Presidential declarations, Colorado has received close to 50 fire assistance awards for suppression and management since 1978, as shown in Table 3-3. The most recent awards in 2010 included the worst wildland fire in state history in terms of destroyed or damaged property with over $200 million in insured loss. Colorado Natural Hazards Mitigation Plan 3 7

8 Table 3 3: FEMA Fire Suppression/Fire Management Assistance, 1978 to 2009 Year Fire Year Fire 1978 Deer Creek Canyon 2002 Million 1980 Bear Trap 2002 Wiley Ridge 1989 Sunnyside 2002 Grizzly Gulch 1990 Old Stage 2002 Again 1994 Wake Complex 2002 Burn Canyon 1994 South Canyon 2002 Big Elk 1994 Roxborough Complex 2002 Panorama 1996 Buffalo Creek 2003 Cloudy Pass 2000 Bobcat 2003 Lincoln Complex 2000 Hi Meadow 2003 Overland 2000 Eldorado 2003 Cherokee Ranch 2001 Armageddon Carter Lake 2003 Buckhorn Creek 2002 Snaking 2004 Picnic Rock 2002 Cuerno Verde 2004 McGruder 2002 Black Mountain 2005 Mason 2002 Schoonover 2006 Mauricio Canyon 2002 Iron Mountain 2006 Mato Vega 2002 Spring Trinidad Complex 2006 Red Apple 2002 Fisher Trinidad Complex 2007 Newcastle 2002 Ute Pass 2008 Ordway 2002 Coal Seam 2008 Nash Ranch 2002 Hayman 2009 Olde Stage 2002 Dierich Creek 2010 Fourmile Canyon 2002 Missionary Ridge 2010 Reservoir Road 2002 Valley Colorado also regularly receives United States Department of Agriculture (USDA) Secretarial Disasters. These declarations typically result from hail, windstorms, drought, early freezes, and grasshopper infestations. Table 3-4 shows Secretarial Disasters since 2003, however, years prior produced many additional declarations. Colorado Natural Hazards Mitigation Plan 3 8

9 Table 3 4: USDA Secretarial Disasters in Colorado, 2003 to 2009 Year Type Declaration Number Declaration Number and Affected Counties 2003 Drought S1797 Baca, Bent, Elbert, Kiowa, Lincoln, Prowers 2003 Drought, Insects S1843 Alamosa, Archuleta, Chaffee, Conejos, Costilla, Crowley, Custer, Dolores, Fremont, Garfield, Hinsdale, Huerfano, La Plata, Lake, Las Animas, Mesa, Mineral, Moffat, Montezuma, Otero, Pueblo, Rio Blanco, Rio Grande, Routt, Saguache 2003 Drought S1890 Cheyenne, Phillips 2004 Drought, Freeze, Hail S1947 Baca, Chaffee, Cheyenne, Custer, Eagle, Fremont, Garfield, Grand, Jackson, Kiowa, Kit Carson, Lake, Lincoln, Phillips, Pitkin, Prowers, Pueblo, Routt, Summit, Yuma 2004 Drought S2009 Moffat 2005 Drought S2031 Huerfano, Las Animas, Rio Blanco /6 2005/ Drought, Freezing Temperatures Drought, Wind, Heavy Rain, Hail Drought, Crop Diseases, Insect Infestation Drought, Crop Diseases, Insect Infestation Drought, Fire, High Winds, Heat Heat, high winds, insect pests, late freeze, drought Heat, high winds, drought S2160 S2188 S2217 S2287 S2327 S2329 S2351 Delta, Kit Carson Crowley, El Paso, Lincoln, Otero, Park, Phillips, Pueblo, Teller, Washington, Yuma Logan Huerfano, Kiowa, Las Animas, Sedgwick Adams, Alamosa, Baca, Broomfield, Chaffee, Cheyenne, Conejos, Costilla, Custer, Denver, Dolores, Douglas, Elbert, Fremont, Hinsdale, Huerfano, Kit Carson, Lake, Las Animas, Mineral, Montezuma, Morgan, Prowers, Pueblo, Rio Grande, Saguache, San Miguel, Weld Arapahoe, Archuleta, Bent, Boulder, Crowley, Delta, El Paso, Gunnison, Jefferson, Kiowa, La Plata, Montrose, Ouray, Park, Phillips, Teller, Washington Eagle, Garfield, Larimer, Logan, Otero, Pitkin, Rio Blanco, Yuma 2006 Drought S2382 Jackson, Lincoln, Mesa, Moffat 2006 Drought S2480 Sedgwick 2008 Drought S2750 Adams, Arapahoe, Baca, Bent, Cheyenne, Crowley, Douglas, El Paso, Elbert, Huerfano, Kiowa, Kit Carson, Las Animas, Lincoln, Logan, Otero, Park, Prowers, Pueblo, Teller, Washington, Weld 2008 Drought S2802 Fremont 2009 Drought S2970 Dolores, Mesa, Montezuma, Montrose, San Miguel Source: USDA Farm Service Agency Colorado Natural Hazards Mitigation Plan 3 9

10 Insured Losses Current insurance industry standards classify a catastrophe as a natural disaster that causes at least $25 million in insured damage. Colorado has experienced 16 such catastrophes since 1984, the majority representing significant hailstorm events as shown in Table 3-5. The most costly catastrophe in Colorado history is a hailstorm that hit the Front Range in July 1990 and caused $625 million in damage. Table 3 5: Colorado Disasters with High Insured Dollar Losses Year Natural Hazard At Time Of Loss Insured Loss (Millions) 2009 Dollars 1984 Hail Tornado (Limon) Hail , Hail Hail Hail Hail Hail Wildfires Winter Storm Hail Hail Tornadoes/Hail June 2009 Hail (Denver Metro) July 2009 Hail (Denver Metro) Hail (Pueblo) Wildfire 200* *Preliminary estimate Source: Rocky Mountain Region Insurance Statistics (Colorado Specific) Other costly disasters in Colorado include wildfires, winter storms, and tornadoes. Prior to 2010, the 2002 wildfire season in Colorado was the most expensive in state history. The overall estimated cost of the Iron Mountain, Coal Seam, Missionary Ridge and Hayman Fires in Colorado is $70.3 million in insured losses. Companies received 1,236 customer claims for the Hayman and Missionary Ridge Fires at a cost of around $56.4 million. The Fourmile Canyon Fire in September 2010 became the costliest fire in Colorado with a preliminary estimate of over $200 in insured losses. Additional events as considered catastrophes from an insurance industry perspective include the most expensive winter storm from snow and ice damage in Colorado history with the blizzard in March The estimated price tag from this storm was nearly Colorado Natural Hazards Mitigation Plan 3 10

11 $93.3 million from more than 28,000 claims filed. Also, in June of 1990, a tornado touched down in Limon, Colorado causing an estimated $20 million in insured damages. Local Mitigation Plans Local mitigation plans were reviewed for new natural hazards for this plan and remain consistent with the natural hazards addressed by this plan. See Section 6 - Counties and Communities for further information on hazards addressed by local planning efforts. Sources Rocky Mountain Insurance Information Association (RMIIA) United States Department of Agriculture (USDA), Farm Service Agency (FSA) Federal Emergency Management Agency (FEMA) Colorado State Archives Colorado Natural Hazards Mitigation Plan 3 11

12 Hazard Profiles Requirement 201.4(c)(2)(i): [The State risk assessment shall include an overview of the] location of all natural hazards that can affect the State, including information on previous occurrences of hazard events, as well as the probability of future hazard events, using maps where appropriate. Primary areas of consideration within hazard profiles in this plan are listed below. Hazard Analysis Summary Definition Characteristics Geographic Location Previous Occurrences Probability of Future Events Magnitude and Severity Previous versions of the plan included pertinent information to achieve complete hazard profiles but were structured in a manner that provided opportunity to enhance organization for the 2010 plan update. Each of the areas of consideration for the hazard profiles and assessment of risk are described below. Hazard Analysis Summary For each hazard, a rollup of the analysis is provided for reference and to use as a tool for determining which hazards may have precedence when it comes to allocating statewide mitigation resources. This hazard analysis summary provides an impact and associated description for geographic location, previous occurrences, future probability, and magnitude and severity. The criteria for each of these impact designations are provided in Table 3-6. Colorado Natural Hazards Mitigation Plan 3 12

13 Table 3 6: Hazard Analysis Summary Category Descriptions Geographic Location Statewide Regional Local Previous Occurrences Perennial Seasonal Sporadic Future Probability Expected Likely Occasional Unlikely Magnitude/Severity Catastrophic Extensive Moderate Minimal Occurring across the state and largely indiscriminate of geologic or environmental considerations. Occurring predominately in sub areas of the state based on location and associated exposure to atmospheric, geologic, or other environmental conditions. Occurring within an impact confined to a small or geographically isolated area or relating to, or characteristic of a particular place. Active throughout the year on multiple occasions or lasting indefinitely. Occurring at specific times of the year or dependent on a particular seasons and associated atmospheric conditions. Occurring at irregular intervals; having no pattern or order in time; appearing singly or at widely scattered localities; dependant on aggravating or cascading circumstances. Annual event or assumed to occur at least one per year. Occurs in the range of about once every 10 years. Occurs only every 11 to 100 years. Considered an once in a lifetime event. Occurs greater than every 100 years. Mass fatality and casualty; significant population displacement or other quality of life impacts; damage to property, facilities, infrastructure resulting in loss of use or accessibility; service disruption; need for outside resources. Isolated deaths and injuries; quality of life impacts; major or long term impact to property, facilities, infrastructure, or critical services. Minimal death or injury; limited quality of life impacts; minor or short term impact on property, facilities, infrastructure, or critical services. No deaths and few injuries; minor quality of life impacts; little or no impact on property, facilities, infrastructure, or critical services. Colorado Natural Hazards Mitigation Plan 3 13

14 Definition and Characteristics General definitions and characteristics of hazards are included in the HIRA to provide a common understanding as to what the natural event is and why it is of enough concern to make it a hazard in Colorado. These definitions and characteristics were reviewed and updated or enhanced for some hazards. Geographic Location Natural hazards occurring in Colorado range from statewide to regional with some specifically associated with the geologic attributes of a localized area. The geographic extent for each hazard is presented in text and supported by tables or maps where available and appropriate. In many cases, the statewide geographic extent of hazards has been refined in this plan update. Previous Occurrences Every county in the state has experienced the adverse affects of natural hazards. Descriptions of previous occurrences, or known hazard incidents, are included to help frame the extent of the hazards impact on areas of Colorado. In some cases, detailed accounts are provided for significant historic hazard events. Occurrences for every hazard were reviewed and updated from the For some hazards detailed historic events and associated deaths, injuries, and total damage by county were included for the first time. The Spatial Hazard Events and Losses Database for the United States (SHELDUS) was used in addition to other sources. SHELDUS based data equally distributes injuries, deaths, and property damages across counties for multi-jurisdictional events. This data was rounded to whole number by county for the purposes of this plan. Future Probability The likelihood of a hazard occurring again looks toward past frequency to assist in determining the probability of future occurrence. For some hazards, the future probability of events is further supported by assumptions that favorable environmental conditions resulting in a hazard event will continue to develop or persist. Magnitude and Severity Assessment of severity in expressed in terms of consequence of impacts such as injuries and fatalities, damage to personal property, infrastructure, state or local critical assets, and the environment, negative affects on the economy, and the degree and extent with which the hazard affects the ability to provide essential services. Magnitude and severity is further considered in the vulnerability assessment and consequence analysis. Natural hazards are grouped into the following areas for the purpose of developing profiles: atmosphere, geologic, and other hazards. This grouping allows for a more Colorado Natural Hazards Mitigation Plan 3 14

15 logical and cohesive approach toward analysis and understanding than if the hazards were presentation in alphabetical order. Atmospheric Hazards Geologic Hazards Other Hazards Drought Extreme Heat Floods Hailstorms Lightning Precipitation Thunderstorms Tornadoes Windstorms Winter Weather Avalanche Earthquake Erosion and Deposition Expansive Soils Landslides, Mud/Debris Flows, Rockfalls Subsidence Wildfire Grasshopper Infestation Colorado Natural Hazards Mitigation Plan 3 15

16 Atmospheric Hazards Drought Extreme Heat Floods Hailstorms Lightning Precipitation Thunderstorms Tornadoes Windstorms Winter Weather Colorado Natural Hazards Mitigation Plan 3 16

17 Drought Aside from a few instances, information provided in this section is summarized from the Colorado Drought Mitigation and Response Plan (2010), a detailed hazard specific annex to the Colorado Pre-Disaster Mitigation Plan that was updated and enhanced as part of this planning effort. Otherwise, the information originated and was updated from the 2007 PDM plan. For additional details, please refer to the drought specific plan. Hazard Profile Summary Consideration Impact Description Geographic Location Statewide Mountains and plains both experience drought. Changes geographically from year to year and decade to decade. Drought in one area of the state may affect other regions. Previous Occurrences Sporadically Drought may occur at any time of the year and be short or long term in development, duration, and ending. Future Probability Likely Atmospheric conditions resulting in severe drought conditions are expected to occur as frequently in the future as in the past. The Colorado Drought Mitigation and Response Plan also notes that, Short duration drought as defined by the three month Standardized Precipitation Index (SPI) occur somewhere in Colorado in nearly nine out of every ten years. Magnitude/Severity Extensive Limited property damage that does not threaten structural integrity; deaths (3 4 per year); and injuries; little or no impact critical services or facilities. May result in significant economic and water resource impacts. Definition Drought may be defined several different ways depending upon the source or impact. The following definitions of drought are considered for this plan: Meteorological drought a period of below-average precipitation. Agricultural drought a period of inadequate water supply to meet the needs of the state s crops and other agricultural operations such as livestock. Hydrological drought deficiencies in surface and subsurface water supplies. Generally measured as streamflow, snowpack, and as lake, reservoir, and groundwater levels. Socioeconomic drought occurs when drought impacts health, well-being, and quality of life, or when a drought starts to have an adverse economic impact on a region. Colorado Natural Hazards Mitigation Plan 3 17

18 Characteristics With its semiarid conditions, drought is a natural part of the Colorado climate. Due to natural variations in climate and precipitation, single season droughts over some portion of the state occur nearly every year. Hydrologic conditions constituting a drought for water users in one location may not constitute a drought for water users elsewhere, or for water users that have a different water supply. Individual water suppliers may use criteria, such as rainfall/runoff, amount of water in storage, or expected supply from a water wholesaler, to define their water supply conditions. The drought issue is further influenced by water rights specific to a state or region. Water is a commodity regulated under a variety of legal doctrines. Geographic Location No portion of the State of Colorado is immune from drought conditions. The effects of drought vary based on where in the state it occurs, when it happens, and how long the drought persists. Droughts that occur in the mountainous regions of the state during winter months may have great affects on the ski and tourism industry. However, drought in one area of the state may also impact other regions. Lack of winter snowfall in the mountains can eventually lead to agricultural impacts on the eastern plains due to decreased streamflows. Reduced reservoir storage from decreased runoff in the mountains can lead to voluntary, or in severe cases, mandatory municipal and/or industrial water usage restrictions on the Front Range. Droughts that occur in populated areas may increase the threat of wildfire in the wildland urban interface areas. Previous Occurrences Several times since the late 1800s Colorado has experienced widespread, severe drought. The most dramatic occurred in the 1930s and 1950s when many states, Colorado included, were affected for several years at a time. Table 3-7 below shows six multi-year droughts experienced in Colorado since Colorado Natural Hazards Mitigation Plan 3 18

19 Table 3 7: Historical Dry and Wet Periods in Colorado Date Dry Wet Duration (years) * * 6 Source: Colorado Drought Mitigation and Response Plan (2010); McKee, et al. *modified for this Plan in 2010 based on input from the CCC Table 3-8 includes a list of years where significant drought conditions occurred somewhere in Colorado since As noted below, in some cases short-lived periods of drought occurred during overall periods of wetter than normal conditions on a statewide basis: Table 3 8: Colorado s Significant Drought Conditions Since Year 1900 The 1930 s Drought The 1950s Drought The 1977 Drought The Dust Bowl drought severely affected much of the United States during the 1930s. During the 1950s, the Great Plains and the southwestern U.S. withstood a five year drought, and in three of these years, drought conditions stretched coast to coast. The 1950s drought was characterized by both decreased rainfall and excessively high temperatures. The area from the Texas panhandle to central and eastern Colorado, western Kansas, and central Nebraska experienced severe drought conditions. During 1976 and 1977, the state experienced record low streamflows at two thirds of the major stream gages, records that held until the 2002 drought Drought Short lived, beginning in the fall of 1980 and lasting until the summer of Drought Significant impacts reported included an increase in wildfires statewide, loss to the winter wheat crops, difficulties with livestock feeding, and impacts to the State s fisheries Drought July 29, the Governor issued an Executive Order proclaiming a Drought Disaster Emergency Declaration for fifteen counties. Colorado Natural Hazards Mitigation Plan 3 19

20 2002 Drought On a statewide basis, 2002 was the most intense single year of drought in Colorado s history. This was an extremely dry year embedded in a longer dry period ( ). These conditions were rated exceptional by the U.S. Drought Monitor and were the most severe drought experienced in the region since the Dust Bowl. Based on studies of tree rings and archaeological evidence from aboriginal cultures, the 2002 drought was the most severe in the recorded history of the state. Source: Colorado Drought Mitigation and Response Plan (2010); NCDC, Colorado Climate Center, Mckee and Doesken, Tronstad and Feuz Case History During 1976 and 1977, the State experienced record-low stream flows at two-thirds of the major stream gages, records that held until the 2002 drought. In addition, the Colorado ski industry estimated revenue losses at $78.6 million; agriculture producers incurred higher crop production costs due to water supply shortages; and numerous municipalities were forced to impose water use restrictions on their customers. The state s agriculture producers and municipalities received over $110 million in federal drought aid as a result of the drought. The drought of 2002 is considered the most intense drought on record. Statewide snowpack was at or near all time lows. What made 2002 so unusual was that all of the State was dry at the same time. By all accounts, soil moisture was nearly depleted in the upper one-meter of the soil profile over broad areas of Colorado by late August was clearly the driest year in over 100 years of record based on streamflow. Future Probability Historical analysis of precipitation shows that drought is a frequent occurrence in Colorado. Short duration drought as defined by the three-month Standardized Precipitation Index (SPI) occur somewhere in Colorado in nearly nine out of every ten years. However, severe, widespread multiyear droughts are much less common. According to the 2004 Drought Water Supply Assessment, there have been six recorded drought incidents totaling 36 dry years which impacted the State of Colorado since 1893, or a span of 111 years. ( = 111 years). This formula evaluates that the probability of a drought occurring in any given year is 32.4 percent. Figure 3-1, from the National Drought Mitigation Center, indicates that most of Colorado has experienced severe or extreme drought between 15 and 19.9 percent of the time from Future analyses of probability and magnitude and severity will improve with the development of improved tools as part of the 2010 update. Colorado Natural Hazards Mitigation Plan 3 20

21 Figure 3 1: Palmer Drought Severity Index, 1895 to 1995 Magnitude and Severity Drought impacts are wide-reaching and may come in different forms, such as economic, environmental, and/or societal. Drought is one of the few hazards with the potential to directly or indirectly impact the entire population of the State, be it from water restrictions, higher water and food prices, reduced air or water quality, or restricted access to recreational areas. The most significant impacts associated with drought in Colorado are those related to water intensive activities such as agriculture, wildfire protection, municipal usage, commerce, tourism, recreation, and wildlife protection. Since 2003, there have been 16 USDA Secretarial Disasters declared for various counties in Colorado. These declarations provided financial assistance to what can be devastating losses in crop production and associated agricultural crop or rangeland revenues. Tourism in Colorado is strengthened by protected areas that are owned and managed by the State. Drought impacts to these assets translate to declines in tourism and related industries. Furthermore, decreased revenues for state agencies resulting from drought can reduce management budgets, which can have a detrimental impact on lands and wildlife. Colorado Natural Hazards Mitigation Plan 3 21

22 Droughts may also result in a reduction of electric power generation and water quality deterioration. Drought conditions can also cause soil to compact, decreasing its ability to absorb water, making an area more susceptible to flash flooding and erosion. A drought may also increase the speed at which dead and fallen trees dry out and become more potent fuel sources for wildfires. Drought may also weaken trees in areas already affected by mountain pine beetle infestations, causing more extensive damage to trees and increasing wildfire risk, at least temporarily. Further analysis of magnitude and severity is provided by sectors and subsectors in the attached drought mitigation plan. The sectors are as follows: Agriculture, Energy, Environment, Municipal and Industrial, Recreation, and Socioeconomic. The recreation, energy, and agricultural sectors were further broken out for more detailed analyses. Recreation was broken into rafting, boating, golf, wildlife viewing, skiing, and hunting, camping, and fishing. The energy sector was broken into mining and power while agriculture has the sub-sectors of green industries, livestock, and crops. Sources Colorado Drought Mitigation and Response Plan (2010) The Drought of 2002 in Colorado, McKee and Doesken Impacts of the 2002 drought on western ranches and public land policies, Western Economics Forum, Tronstad and Feuz (2002) Colorado Climate Center (CCC) Colorado Water Resources Research Institute National Weather Service (NWS), National Climatic Data Center (NCDC) Colorado Natural Hazards Mitigation Plan 3 22

23 Extreme Heat Hazard Profile Summary Consideration Impact Description Geographic Location Regional Areas of the state with highest temperatures are concentrated along the front range and eastern plains, the Grand Valley, and extreme southwest. Previous Occurrences Seasonal Every few years in high temperature prone areas of the state, average temperatures will be at extreme highs for one to three weeks. Future Probability Occasional Each year, any number of days with extreme heat exceeds normal high temperatures around the state. High temperature events of prolonged duration are not frequent. Magnitude/Severity Moderate Limited property damage that does not threaten structural integrity; minor injuries; little or no impact critical services or facilities. Definition Extreme heat conditions are defined by summertime weather that is substantially hotter and/or more humid than average for a location at that time of year. This definition for extreme heat may be refined with considerations such as summertime temperatures that hover 10 degrees or more above the average high temperature for the region and last for several week. The Heat Index (HI) or the "Apparent Temperature" is an accurate measure of how hot it actually feels when the Relative Humidity (RH) is added to the actual air temperature. The heat index may be used to help determine when an extreme heat event is occurring. Characteristics North American summers are typically hot with heat waves occurring in one or more parts of the United States each year. East of the Rockies, extreme heat tends to combine both high temperature and high humidity; although some of the worst heat waves have been catastrophically dry. Over the last 30 years in the United States, excessive heat accounts for more reported deaths annually than hurricanes, floods, tornadoes, and lightning combined. The extreme heat hazard in Colorado is often underestimated because other natural hazards occur more frequently and its effects can vary based on region and vulnerable population within the State. Colorado Natural Hazards Mitigation Plan 3 23

24 Figure 3 2: Weather Fatalities in the United States, 1977 to 2006 Source: National Weather Service Humid or muggy conditions, which add to the discomfort of high temperatures, occur when a "dome" of high atmospheric pressure traps hazy, damp air near the ground. Excessively dry and hot conditions can provoke dust storms and low visibility. Heat alert procedures from the National Weather Service (NWS) are based mainly on Heat Index Values. The Heat Index, sometimes referred to as the apparent temperature and given in degrees Fahrenheit, is a measure of how hot it really feels when relative humidity is factored with the actual air temperature. The NWS heat index chart is presented in Figure 3-3. Colorado Natural Hazards Mitigation Plan 3 24

25 Figure 3 3: NOAA s National Weather Service Heat Index Since heat index values were devised for shady, light wind conditions, exposure to full sunshine can increase heat index values by up to 15 degrees F. Geographic Location Average temperatures across Colorado vary as extremely as, and in relation to, the changes in elevation. The eastern plains and Western Slope of the state experience average temperatures in July between 70 and 80 degrees. At higher elevations, these temperatures tend to be lower with highs reaching into the 60s. Previous Occurrence During 2008, Denver's 87 year-old record for the number of consecutive days above 90 degrees F was broken. The new record of twenty-four consecutive days surpassed the previous record by almost a week. On August 1st, it reached 104 degrees, breaking a record set in 1938 and on August 2nd, it reached 103 degrees, breaking a record set in Table 3-9 shows Denver s historic count of 90 degrees or higher days since The average number of 90 degree days per in Denver is 33. In 2000, the number of days was nearly double the average with 61 days of 90 degree temperatures or higher. Colorado Natural Hazards Mitigation Plan 3 25

26 Table 3 9: Denver s 90 Degree Days Year Total Days Source: NWS Extreme high temperatures recorded in Colorado counties are shown in Table Although viewing record highs does not necessarily equate to prolonged extreme heat events, the table provides an indication of potential temperature extremes across the state. Table 3 10: Summary of Extreme High Temperatures in Colorado by County: County Temperature (F)* County Temperature (F)* Adams 105 La Plata 102 Alamosa 96 Lake 86 Arapahoe 108 Larimer 102 Archuleta 99 Las Animas 103 Baca 111 Lincoln NA Bent 112 Logan 110 Boulder 106 Mesa 108 Chaffee 95 Mineral 97 Cheyenne 108 Moffat 104 Clear Creek 84 Montezuma 101 Conejos 95 Montrose 110 Costilla 97 Morgan 107 Crowley NA Otero 110 Custer 94 Ouray 91 Delta 106 Park 95 Denver 103 Phillips 109 Dolores 99 Pitkin NA Douglas 99 Prowers 109 Eagle 100 Pueblo 108 El Paso 99 Rio Blanco 108 Elbert 100 Rio Grande 93 Colorado Natural Hazards Mitigation Plan 3 26

27 County Temperature (F)* County Temperature (F)* Fremont 105 Routt 98 Garfield 104 Saguache NA Gilpin NA San Juan 88 Grand 94 San Miguel 97 Gunnison 98 Sedgwick 109 Hinsdale 98 Summit 98 Huerfano 101 Teller NA Jackson 96 Washington NA Jefferson 103 Weld NA Kiowa 110 Yuma NA Kit Carson 107 *As Recorded At A Natural Resources Conservation Service (U.S.D.A.) Temperature And Precipitation Stations (TAPS) Note: Not All Data Covers A 30 Year Period. Source: The average number of days in Colorado with temperatures greater than or equal to 90 degrees and 100 degrees F are shown in Figure 3-4. Portions of Baca County in the southeastern corner of the state may have 80 or more days of 90 degrees F or greater temperatures a year. Most of the county may experience fifteen to eighteen days of 100 degrees F or greater. Figure 3 4: Number of Days with Temperatures Greater than or Equal to 90 and 100 Degrees 100 Degrees 90 Degrees Source: High Plains Regional Climate Center Future Probability Since the record hot year of 1998, six of the last ten years ( ) have had annual average temperatures that fall in the hottest 10 percent of all years on record for the Colorado Natural Hazards Mitigation Plan 3 27

28 United States. This example supports a shift towards a warmer climate with an increase in extreme high temperatures and a reduction in extreme low temperatures. These types of changes have been apparent in the western half of North America. Figure 3-5 shows that since before 1900, Colorado much like the rest of the county is in a warming cycle. Statewide, the average temperature over the last 110 years is about 45 degrees F. The trend line for state temperatures during this time has increased from 44 to 46 degrees. Figure 3 5: Colorado Annual Average Temperature, 1895 to 2010 Source: National Weather Service Colorado Natural Hazards Mitigation Plan 3 28

29 Magnitude and Severity Health Impacts The July 1995 heat wave killed 522 people in Chicago alone. Research by the Centers for Disease Control (CDC) found that on a national average 384 people were killed by excessive heat each year during the period 1979 to This is significantly higher than the numbers reported in the National Weather Service's Summary of Natural Hazards Deaths. This is due in part to the research methodology of local NWS offices relying on published accounts of events rather than death certificates. Attributing excessive heat as a cause or contributing factor in mortality has varied considerably across jurisdictions. This has led to speculation that the actual, as opposed to reported, death toll is much higher. For example, one study suggests that the actual death toll of the 1980 heat wave may be 5,000, not the official number of 1,700. Other studies indicate that diagnosis of heat-related deaths have been regularly underestimated by 22 percent to 100 percent. The population of Colorado has become less sensitive to the impacts of excessive heat events over the course of the past 30 to 40 years despite rising urban temperatures. This is a trend common to most major cities across the United States as result of the increased availability and use of air conditioning and the implementation of social programs aimed at caring for high-risk individuals. Colorado Natural Hazards Mitigation Plan 3 29

30 Figure 3 5: Heat related mortality trends across the U.S. Figure 7. Annual heat related mortality rates (excess deaths per standard million population). Each histogram bar indicates a different decade (from left to right, 1970s, 1980s, 1990s). (Source: Davis et al., 2003b). (Source: SPPI 2008) For nearly all cities, including Denver, the number of heat-related deaths is declining (the bars are get smaller) as shown in Figure 3-5. This indicates that there has been a decrease in heat-related deaths over time meaning that the population has become better adapted to heat waves. This adaptation is most likely a result of improvements in medical technology, access to air-conditioned homes, cars, and offices, increased public awareness of potentially dangerous weather situations, and proactive responses of municipalities during extreme weather events. Colorado Natural Hazards Mitigation Plan 3 30

31 Regardless of any trends indicating heat-related deaths are declining, extreme heat events remain a danger. Specific high-risk groups typically experience a disproportionate number of health impacts from extreme heat conditions. The populations that have physical, social, and economic factors and the specific actions that make them at high risk include: Older persons (age > 65) Infants (age < 1) The homeless The poor People who are socially isolated People with mobility restrictions or mental impairments People taking certain medications (e.g., for high blood pressure, depression, insomnia) People engaged in vigorous outdoor exercise or work or those under the influence of drugs or alcohol. Each year children die from hyperthermia as a result of being left in parked vehicles. Hyperthermia is an acute condition that occurs when the body absorbs more heat than it can dissipate. Hyperthermia can occur even on a mild day. Studies have shown that the temperature inside a parked vehicle can rapidly rise to a dangerous level for children, adults and pets. Leaving the windows slightly open does not significantly decrease the heating rate. The effects can be more severe on children because their bodies warm at a faster rate than adults. Those at greatest risk of death in heat waves are the urban-dwelling elderly without access to an air-conditioned environment for at least part of the day. Thus the issues of prevention and mitigation combine issues of the aging and of public health. As shown in Figure 3-6, between 1999 and 2003, heat related deaths of persons 65 and older were significantly higher than other age groups. Colorado Natural Hazards Mitigation Plan 3 31

32 Figure 3 6: Number of Heat Related Deaths, by Sex and Age Group in the United States, 1999 to 2003 Source: United States Center for Disease Control Transportation Impacts There are several impacts on transportation documented in case studies. Aircraft lose lift at high temperatures and major airports have been closed due to periods of extreme heat that made aircraft operations unsafe. Highways and roads are damaged by excessive heat as asphalt roads soften and concrete roads have been known to "explode" lifting 3 to 4 foot pieces of concrete. During the 1980 heat wave, hundreds of miles of highways buckled. Stress is placed on automobile cooling systems, diesel trucks and railroad locomotives which lead to an increase in mechanical failures. Train rails develop sun kinks and distort. Refrigerated goods experience a significant greater rate of spoilage due to extreme heat. Agriculture Various sectors of the agriculture community are affected by extreme heat. Livestock, such as rabbits, poultry, pigs, and cows are severely impacted by heat waves. Millions of birds have been lost during heat waves and milk production and cattle reproduction also Colorado Natural Hazards Mitigation Plan 3 32

33 decreases during heat waves. High temperatures at the wrong time inhibits a crop yields and wheat, rice, maize, potato, and soybean crop yields can all be significantly reduced by extreme high temperatures at key development stages. Energy The electric transmission system is impacted when power lines sag in high temperatures and can lead to power outages. The combination of extreme heat and the added demand for electricity to run air conditioning causes transmission line temperatures to rise. The demand for electric power during heat waves is well documented. In 1980, consumers paid $1.3 billion more for electric power during the summer than the previous year. The demand for electricity, 5.5 percent above normal, outstripped the supply, causing electric companies to have rolling black outs. Water Resources The demand for water increases during periods of hot weather. In extreme heat waves, water is used to cool bridges and other metal structures susceptible to heat failure. This causes a reduced water supply and pressure in many areas. This may also contribute to fire suppression problems for both urban and rural fire departments. The rise in water temperature during heat waves contributes to the degradation of water quality and negatively impacts fish populations. It can also lead to the death of many other organisms in the water ecosystem. High temperatures are also linked to rampant algae growth that may result in fish kills in rivers and lakes. Sources Cooperative Institute for Research in the Atmosphere (CIRA) Science and Public Policy Institute (SPPI), 2008 United States Global Change Research Program, 2008 National Weather Service (NWS) National Oceanic and Atmospheric Administration (NOAA) Federal Emergency Management Agency (FEMA) United States Centers for Disease Control (CDC) Colorado Natural Hazards Mitigation Plan 3 33

34 Floods Information provided in this section is primarily summarized and paraphrased from the Flood Hazard Mitigation Plan for Colorado (2010). The flood specific plan is a detailed hazard specific annex to the State Plan that was updated and enhanced as part of this planning effort. For a more in-depth discussion on risk, please refer to the flood specific plan. Hazard Analysis Summary Consideration Impact Description Geographic Location Statewide Flood prone areas have been identified in 268 of 270 cities and towns and in all of the 64 counties in Colorado. Previous Occurrences Seasonal Notable flood events from 1864 to 2010 include dozens of events. These event totals included significant deaths (363) and damages ($5.8 Million). Future Probability Likely In addition to annual minor flooding events, Colorado experiences major floods every 5 years on average. Magnitude/Severity Extensive Major floods may induce property damage that threatens structural integrity, result deaths and injuries, and impact critical services, facilities, and infrastructure. Between 20 and 30 large magnitude floods (in terms of peak discharge) occur somewhere in Colorado every year with varying impact depending on location. Definition A flood is a general and temporary condition of partial or complete inundation of normally dry land areas from: (1) the overflow of stream banks, (2) the unusual and rapid accumulation of runoff of surface waters from any source, or (3) mudflows or the sudden collapse of shoreline land. Flooding results when the flow of water is greater than the normal carrying capacity of the stream channel or accumulates faster than surface absorbency allows. The floodplain is land adjoining the channel of a river, stream, lake or other watercourse or water body that is susceptible to flooding. Characteristics The causes of floods relate directly to the accumulation of water from precipitation, rapid snowmelt, or the failure of human made structures, such as dams or levees. Floods caused by precipitation are further classified as coming from: Colorado Natural Hazards Mitigation Plan 3 34