Risk Assessment

- DMA Requirement §201.6(c)(2):

[The plan shall include] A risk assessment that provides the factual basis for activities proposed in the strategy to reduce losses from identified hazards. Local risk assessments must provide sufficient information to enable the jurisdiction to identify and prioritize appropriate mitigation actions to reduce losses from identified hazards. The risk assessment shall include: A description of the type, location, and extent of all natural hazards that can affect the jurisdiction. The plan shall include information on previous occurrences of hazard events and on the probability of future hazard events. A description of the jurisdiction’s vulnerability to the hazards described in paragraph (c)(2)(i) of this section. This description shall include an overall summary of each hazard and its impact on the community. The plan should describe vulnerability in terms of: The types and numbers of existing and future buildings, infrastructure, and critical facilities located in the identified hazard areas; An estimate of the potential dollar losses to vulnerable structures identified in paragraph (c)(2)(ii)(A) of this section and a description of the methodology used to prepare the estimate; Providing a general description of land uses and development trends within the community so that mitigation options can be considered in future land use decisions. (iii) For multi-jurisdictional plans, the risk assessment section must assess each jurisdiction’s risks where they vary from the risks facing the entire planning area.

As defined by the Federal Emergency Management Agency (FEMA), risk is a combination of hazard, vulnerability, and exposure. “It is the impact that a hazard would have on people, services, facilities, and structures in a community and refers to the likelihood of a hazard event resulting in an adverse condition that causes injury or damage.”

The risk assessment process identifies and profiles relevant hazards and assesses the exposure of lives, property, and infrastructure to these hazards. The process allows for a better understanding of a jurisdiction’s potential risk to natural hazards and provides a framework for developing and prioritizing mitigation actions to reduce risk from future hazard events.

This risk assessment followed the methodology described in the FEMA publication: Local Mitigation Planning Handbook (March 2013), which breaks the risk assessment down to a four-step process:

Describe Hazards

Identify Community Assets

Analyze Risks

Summarize Vulnerability

A key step in preventing disaster losses in Jefferson County is developing a comprehensive understanding of the hazards that pose risks to its communities. The following terms facilitate comparisons between communities and can be found throughout the Plan.

Hazard: Event or physical condition that has the potential to cause fatalities, injuries, property damage, infrastructure damage, agricultural loss, damage to the environment, interruption of business, other types of harm or loss

Risk: Product of a hazard’s likelihood of occurrence and its consequences to society; the estimated impact that a hazard would have on people, services, facilities, and structures in a community

Vulnerability: Degree of susceptibility to physical injury, harm, damage, or economic loss; depends on an asset’s construction, contents, and economic value of its functions.

Data collected through this process has been incorporated into the following sections of this section:

Section 4.1 Hazard Identification identifies the hazards that threaten the planning area and describes why some hazards have been omitted from further consideration.

Section 4.2 Asset Summary describes the people, property, infrastructure, and resources potentially exposed to risk across Jefferson.

Section 4.3 Hazard Profiles discusses the hazards that threaten the county, describes previous occurrences, their geographic extent, potential magnitude, and assesses their probability of future occurrence. It also includes a vulnerability assessment for each hazard, considering assets at risk, critical facilities, and future development trends.

The Jurisdictional Annexes discuss each participating jurisdiction’s individual exposure to natural hazards, including how the threat of hazards varies across the planning area along with each jurisdiction’s specific vulnerabilities.

Hazard Identification

The Hazard Mitigation Planning Committee (HMPC) conducted a hazard identification study to determine the hazards that threaten the planning area.

Results and Methodology

Using existing hazards data, plans from participating jurisdictions, and input gained through planning and public meetings, the HMPC agreed upon a list of hazards that could affect Jefferson County. Hazards data was obtained from various federal, state, and local sources such as FEMA, the Colorado Geological Survey (CGS), the Colorado Dam Safety Branch (DSB), the National Oceanic and Atmospheric Administration’s (NOAA) National Center for Environmental Information (NCEI), the United States Geological Survey (USGS), and the Colorado Division of Homeland Security and Emergency Management (including the 2018 Colorado State Hazard Mitigation Plan), among others. The hazards evaluated in this plan include those that have occurred historically or have the potential to cause significant human and/or monetary losses in the future.

Sixteen natural hazards were profiled in the 2016 Jefferson County Hazard Mitigation Plan. The HMPC reviewed all of these hazards and determined they were all still relevant and should be continued into the 2021 Plan update. Additionally, the HMPC reviewed a number of human-caused hazards and elected to include the two of greatest concern as hazards new to the plan: cyber attack and pandemic.

Each of the hazards were identified based on geographic extent, previous occurrences, potential for future occurrence, and a discussion on the potential severity and magnitude of the event. The potential impacts of climate change on each hazard were also considered. Once these elements were examined, each hazard was assigned an overall rating for the County.

The following hazards were determined to have a high significance:

Dam Failure

Flood

Hailstorm

Wildfire

Severe Winter Storms

The following hazards were determined to have a medium significance:

Cyber Attack (new)

Drought

Earthquake

Erosion and Deposition

Expansive Soils

Landslides/Debris Flows/Rockfalls

Lightning

Pandemic (new)

Subsidence

Tornado

Windstorm

The following hazards were determined to have a low significance:

Avalanche

Extreme Temperatures

For many hazards, the risk varies between jurisdictions; the jurisdictional annexes provide more explicit detail to explain the variance levels.

Hazard Identification Summary

reflects the hazard identification summaries discussed in detail in the rest of this section. The table is based on the Jefferson County Hazards Identification Worksheet, but also reflects the input from the HMPC to address magnitude and severity, which in some cases altered the overall rating of the hazard compared to the other hazards profiled. When viewing these ratings, it is particularly important to remember that the hazards are all possible in the planning area, and therefore are potentially dangerous. The overall rating is a method of prioritizing hazards relative to one another for the development of mitigation actions and goals.

Table 4-1 Hazards Identification Summary

Hazard	Geographic Extent	Probability of Future Occurrence	Probability of Future Occurrence	Potential Severity/Magnitude	Overall Significance
Avalanche	Negligible	Unlikely	Unlikely	Negligible	Low
Cyber Attack	Significant	Likely	Likely	Limited	Medium
Dam Failure	Extensive	Occasional	Occasional	Critical	High
Drought	Extensive	Likely	Likely	Critical	High
Earthquake	Significant	Unlikely	Unlikely	Catastrophic	Medium
Erosion and Deposition	Significant	Likely	Likely	Critical	Medium
Expansive Soils	Extensive	Likely	Likely	Limited	Medium
Extreme Temperatures	Extensive	Likely	Likely	Limited	Low
Flood	Limited	Likely	Likely	Critical	High
Hailstorm	Significant	Likely	Likely	Critical	High
Landslide/Debris/Rockfall	Limited	Likely	Likely	Limited-Negligible	Medium
Lightning	Limited	Highly Likely	Highly Likely	Limited	Medium
Pandemic	Extensive	Occasional	Occasional	Critical	High
Severe Winter Storms	Extensive	Likely	Likely	Critical	High
Subsidence	Limited	Occasional	Occasional	Limited	Medium
Tornado	Limited	Likely	Likely	Limited	Medium
Wildfire	Significant	Highly Likely	Highly Likely	Critical	High
Windstorm	Significant	Highly Likely	Highly Likely	Limited	Medium
Geographic Extent Negligible: Less than 10 percent of planning area or isolated single- point occurrences Limited: 10 to 25 percent of the planning area or limited single-point occurrences Significant: 25 to 75 percent of planning area or frequent single- point occurrences Extensive: 75 to 100 percent of planning area or consistent single- point occurrences Potential Severity/Magnitude Negligible: Less than 10 percent of property is severely damaged, facilities and services are unavailable for less than 24 hours, injuries and illnesses are treatable with first aid or within the response capability of the jurisdiction. Limited: 10 to 25 percent of property is severely damaged, facilities and services are unavailable for between 1 and 7 days, injuries and illnesses require sophisticated medical support that does not strain the response capability of the jurisdiction, or results in very few permanent disabilities. Critical: 25 to 50 percent of property is severely damaged, facilities and services are unavailable or severely hindered for 1 to 2 weeks, injuries and illnesses overwhelm medical support for a brief period of time, or result in many permanent disabilities and a few deaths. Catastrophic: More than 50 percent of property is severely damaged, facilities and services are unavailable or hindered for more than 2 weeks, the medical response system is overwhelmed for an extended period of time or many deaths occur.	Geographic Extent Negligible: Less than 10 percent of planning area or isolated single- point occurrences Limited: 10 to 25 percent of the planning area or limited single-point occurrences Significant: 25 to 75 percent of planning area or frequent single- point occurrences Extensive: 75 to 100 percent of planning area or consistent single- point occurrences Potential Severity/Magnitude Negligible: Less than 10 percent of property is severely damaged, facilities and services are unavailable for less than 24 hours, injuries and illnesses are treatable with first aid or within the response capability of the jurisdiction. Limited: 10 to 25 percent of property is severely damaged, facilities and services are unavailable for between 1 and 7 days, injuries and illnesses require sophisticated medical support that does not strain the response capability of the jurisdiction, or results in very few permanent disabilities. Critical: 25 to 50 percent of property is severely damaged, facilities and services are unavailable or severely hindered for 1 to 2 weeks, injuries and illnesses overwhelm medical support for a brief period of time, or result in many permanent disabilities and a few deaths. Catastrophic: More than 50 percent of property is severely damaged, facilities and services are unavailable or hindered for more than 2 weeks, the medical response system is overwhelmed for an extended period of time or many deaths occur.	Geographic Extent Negligible: Less than 10 percent of planning area or isolated single- point occurrences Limited: 10 to 25 percent of the planning area or limited single-point occurrences Significant: 25 to 75 percent of planning area or frequent single- point occurrences Extensive: 75 to 100 percent of planning area or consistent single- point occurrences Potential Severity/Magnitude Negligible: Less than 10 percent of property is severely damaged, facilities and services are unavailable for less than 24 hours, injuries and illnesses are treatable with first aid or within the response capability of the jurisdiction. Limited: 10 to 25 percent of property is severely damaged, facilities and services are unavailable for between 1 and 7 days, injuries and illnesses require sophisticated medical support that does not strain the response capability of the jurisdiction, or results in very few permanent disabilities. Critical: 25 to 50 percent of property is severely damaged, facilities and services are unavailable or severely hindered for 1 to 2 weeks, injuries and illnesses overwhelm medical support for a brief period of time, or result in many permanent disabilities and a few deaths. Catastrophic: More than 50 percent of property is severely damaged, facilities and services are unavailable or hindered for more than 2 weeks, the medical response system is overwhelmed for an extended period of time or many deaths occur.	Probability of Future Occurrences Unlikely: Less than 1 percent probability of occurrence in the next year, or has a recurrence interval of greater than every 100 years. Occasional: Between a 1 and 10 percent probability of occurrence in the next year, or has a recurrence interval of 11 to 100 years. Likely: Between 10 and 90 percent probability of occurrence in the next year, or has a recurrence interval of 1 to 10 years Highly Likely: Between 90 and 100 percent probability of occurrence in the next year, or has a recurrence interval of less than 1 year. Overall Significance Low: Two or more of the criteria fall in the lower classifications or the event has a minimal impact on the planning area. Also used for hazards with a minimal or unknown record of occurrences and impacts or for hazards with minimal mitigation potential. Medium: The criteria fall mostly in the middle ranges of classifications and the event’s impacts on the planning area are noticeable but not devastating. Also used for hazards with a high impact rating but an extremely low frequency. High: The criteria consistently fall along the high ranges of the classification and the event exerts significant and frequent impacts on the planning area. Also used for hazards with a high psychological impact or for hazards that the jurisdiction identifies as particularly relevant.	Probability of Future Occurrences Unlikely: Less than 1 percent probability of occurrence in the next year, or has a recurrence interval of greater than every 100 years. Occasional: Between a 1 and 10 percent probability of occurrence in the next year, or has a recurrence interval of 11 to 100 years. Likely: Between 10 and 90 percent probability of occurrence in the next year, or has a recurrence interval of 1 to 10 years Highly Likely: Between 90 and 100 percent probability of occurrence in the next year, or has a recurrence interval of less than 1 year. Overall Significance Low: Two or more of the criteria fall in the lower classifications or the event has a minimal impact on the planning area. Also used for hazards with a minimal or unknown record of occurrences and impacts or for hazards with minimal mitigation potential. Medium: The criteria fall mostly in the middle ranges of classifications and the event’s impacts on the planning area are noticeable but not devastating. Also used for hazards with a high impact rating but an extremely low frequency. High: The criteria consistently fall along the high ranges of the classification and the event exerts significant and frequent impacts on the planning area. Also used for hazards with a high psychological impact or for hazards that the jurisdiction identifies as particularly relevant.	Probability of Future Occurrences Unlikely: Less than 1 percent probability of occurrence in the next year, or has a recurrence interval of greater than every 100 years. Occasional: Between a 1 and 10 percent probability of occurrence in the next year, or has a recurrence interval of 11 to 100 years. Likely: Between 10 and 90 percent probability of occurrence in the next year, or has a recurrence interval of 1 to 10 years Highly Likely: Between 90 and 100 percent probability of occurrence in the next year, or has a recurrence interval of less than 1 year. Overall Significance Low: Two or more of the criteria fall in the lower classifications or the event has a minimal impact on the planning area. Also used for hazards with a minimal or unknown record of occurrences and impacts or for hazards with minimal mitigation potential. Medium: The criteria fall mostly in the middle ranges of classifications and the event’s impacts on the planning area are noticeable but not devastating. Also used for hazards with a high impact rating but an extremely low frequency. High: The criteria consistently fall along the high ranges of the classification and the event exerts significant and frequent impacts on the planning area. Also used for hazards with a high psychological impact or for hazards that the jurisdiction identifies as particularly relevant.

Hazards Not Profiled

Other hazards were discussed by the HMPC but ultimately not included in this plan. Thunderstorm is not identified as an individual hazard, but is recognized for its role in the flood, lightning, and windstorm hazards, and addressed accordingly in those hazard profiles. Fog was also discussed and determined that it is not a true disaster-level hazard for the planning area. The volcano hazard was also removed due to the extraordinary circumstances required for such a disaster event to severely impact the planning area. The natural hazards of coastal erosion, coastal storm, hurricane, and tsunami were excluded from this plan because they are not applicable in Jefferson County.

Several other human-caused hazards were also considered, to include hazardous materials incidents, active threats, transportation accidents, and infrastructure failures. While all those hazards have the potential to impact Jefferson County, the HMPC elected to focus mitigation efforts on the two human- caused hazards that present the greatest risk: cyber attack and pandemic.

It is important to be aware that hazard events that happen outside of the County boundaries also can have direct and indirect impacts to Jefferson County. For instance, transportation routes or power supply could be interrupted by severe winter storms or wildfire hazards outside of the County.

Disaster Declaration History

One method the HMPC used to identify hazards was the researching of past events that triggered federal and/or state emergency or disaster declarations in the planning area. Federal and/or state disaster declarations may be granted when the severity and magnitude of an event surpasses the ability of the local government to respond and recover. Disaster assistance is supplemental and sequential. When the local government’s capacity has been surpassed, a state disaster declaration may be issued, allowing for the provision of state assistance. Should the disaster be so severe that both the local and state governments’ capacities are exceeded, a federal emergency or disaster declaration may be issued allowing for the provision of federal assistance.

The federal government may issue a disaster declaration through FEMA, the U.S. Department of Agriculture (USDA), and/or the Small Business Administration (SBA). FEMA also issues emergency declarations, which are more limited in scope and without the long-term federal recovery programs of major disaster declarations. The quantity and types of damage are the determining factors. The Fire Management Assistance Grant Program provides funding “for the mitigation, management, and control of fires on publicly or privately owned forests or grasslands, which threaten such destruction as would constitute a major disaster.” The quantity and types of damages, as well as the type of event, determine the source of federal aid.

provides information on the 13 federal emergencies and disasters declared in Jefferson County between 1953 and January 2021.

Table 4-2 Federal Disaster Declarations in Jefferson County

Year	Declaration	Disaster Type
1969	Federal Disaster Declaration	Severe Storms and Flooding
1973	Federal Disaster Declaration	Heavy Rains, Snowmelt
2000	Fire Management Assistance Declaration	High Meadows Fire
2002	Fire Management Assistance Declaration	Schoonover Fire, Black Mountain Fire, Snaking Fire, and Hayman Fire
2003	Emergency Declaration	Snow
2005	Emergency Declaration	Hurricane Katrina Evacuation*
2007	Emergency Declaration	Snow
2011	Fire Management Assistance Declaration	Indian Gulch Fire
2012	Fire Management Assistance Declaration	Lower North Fork Fire
2012	USDA Drought Declaration (Primary S3260)	Drought, excessive heat, high winds
2013	Emergency Declaration Federal Disaster Declaration	Severe Storms, Flooding, Landslides and Mudslides
2020	Emergency Declaration and Federal Disaster Declaration	COVID-19 Pandemic

Source: State of Colorado Natural Hazards Mitigation Plan, 2013; Federal Emergency Management Agency, PERI Presidential Disaster Declaration Site. U.S. Department of Agriculture; (*) indicates that Jefferson County was included in the declaration but did not receive funding.

A USDA declaration will result in the implementation of the Emergency Loan Program through the Farm Services Agency. The SBA also offers low interest loans for eligible businesses that suffer economic losses in declared and contiguous counties that have been declared by the USDA. This program enables eligible farmers and ranchers in the affected county as well as contiguous counties to apply for low interest loans. In 2012 the USDA streamlined the declaration process which now provides for nearly an automatic designation for any county in which drought conditions, as reported in the U.S. Drought Monitor when any portion of a county meets the D2 (Severe Drought) drought intensity value for eight consecutive weeks. A county that has a portion of its area in a drought intensity value of D3 (Extreme Drought) or higher at any time during the growing season also would be designated as a disaster area. USDA Declarations since that covered Jefferson County are shown in

Table 4-3 USDA Declarations Including Jefferson County

Year	Declaration	Disaster Type
2012	S3260	Drought, excessive heat, high winds
2013	S3456	Drought, excessive heat, high winds, wildfire, insects
2013	S3548	Drought, excessive heat, high winds, wildfire, insects
2018	S4365	Hail and high wind
2018	S4386	Drought
2018	S4408	Drought
2019	S4468	Drought
2019	S4481	Drought

Year	Declaration	Disaster Type
2020	S4798	Drought
2020	S4848	Drought

Source: U.S. Department of Agriculture

Asset Summary

Population and Structures

shows the estimated total population and number of housing units for each jurisdiction based on the most recent American Community Survey and Colorado State Demography Office data.

Jurisdictions that straddle County boundaries are indicated by an asterisk, and the numbers listed for these jurisdictions only represent the Jefferson County portion.

Table 4-4 Population and Housing Unit Exposure by Jurisdiction

Jurisdiction	2019 Population Estimate	2019 Housing Units Estimate
Arvada*	117,859	42,558
Bow Mar*	300	95
Edgewater	5,352	1,697
Golden	20,828	6,134
Lakeside	8	1
Lakewood	158,410	51,150
Littleton*	2,683	800
Morrison	436	135
Mountain View	536	241
Westminster*	44,162	15,090
Wheat Ridge	31,273	12,141
Unincorporated	201,234	76,455
Grand Total	583,081	206,497

Source: Colorado Department of Local Affairs Demography Section. * Only includes the portion within Jefferson County.

Building value assessments in this plan are based on data from the Jefferson County’s Assessor’s Office. shows the total property inventory from the Assessor’s Office. (The Assessor’s Office assigns values to buildings for the specific purpose of valuation for ad valorem tax purposes, and values represented may not reflect actual building replacement values.) An address points layer was used as the basis for estimating building counts. The Assessor does not maintain data about the contents of structures, therefore the contents values shown in the table are estimates based upon the structure value using FEMA recommended values (typically 50% for residential structures, 100% for commercial, 100% for agricultural, 150% for industrial, 100% for mixed use and 100% for exempt). summarizes the property inventory for the County and each participating jurisdiction with detail by property type, including jurisdictions which may not be participating in the plan.

Table 4-5 Jefferson County’s Building Inventory and Value Summary by Jurisdiction

Jurisdiction	Improved Parcels	Building Count	Improved Value	Content Value	Total Value
Arvada*	42,022	43,997	$14,257,089,578	$7,838,936,533	$22,096,026,111
Bow Mar*	95	95	$54,914,896	$27,457,448	$82,372,344
Edgewater	1,480	1,807	$442,322,263	$256,618,931	$698,941,194
Golden	5,866	6,955	$3,581,405,037	$2,429,883,569	$6,011,288,606
Lakeside	14	27	$28,589,790	$28,589,790	$57,179,580
Lakewood	49,390	54,129	$18,577,041,933	$10,715,684,254	$29,292,726,187
Littleton*	803	803	$352,400,836	$352,400,836	$704,801,672
Morrison	155	188	$65,397,995	$42,262,140	$107,660,135
Mountain View	246	273	$46,888,818	$27,130,145	$74,018,963
Westminster*	15,050	15,691	$5,793,485,591	$3,387,532,303	$9,181,017,894
Wheat Ridge	11,165	13,505	$3,635,566,208	$2,219,156,222	$5,854,722,430
Unincorporated	76,220	79,412	$29,606,470,107	$15,953,167,281	$45,559,637,388
Grand Total	202,506	216,882	$76,441,573,052	$43,278,819,451	$119,720,392,503

Source: Jefferson County Assessor October 2020, FEMA HAZUS

• Only includes the portion within Jefferson County.

Table 4-6 Jefferson County’s Building Inventory and Value Detail by Jurisdiction

Jurisdiction	Property Type	Improved Parcels	Building Count	Improved Value	Content Value	Total Value
Arvada*	Agriculture	8	8	$2,760,667	$2,760,667	$5,521,334
Arvada*	Commercial	515	856	$550,997,194	$550,997,194	$1,101,994,388
Arvada*	Exempt	125	144	$312,137,969	$312,137,969	$624,275,938
Arvada*	Industrial	199	247	$212,035,772	$318,053,658	$530,089,430
Arvada*	Mixed Use	147	184	$130,816,114	$130,816,114	$261,632,228
Arvada*	Residential	41,028	42,558	$13,048,341,862	$6,524,170,931	$19,572,512,793
Arvada*	Total	42,022	43,997	$14,257,089,578	$7,838,936,533	$22,096,026,111
Bow Mar*	Residential	95	95	$54,914,896	$27,457,448	$82,372,344
Bow Mar*	Total	95	95	$54,914,896	$27,457,448	$82,372,344
Edgewater	Commercial	45	79	$35,300,820	$35,300,820	$70,601,640
Edgewater	Exempt	12	13	$24,162,201	$24,162,201	$48,324,402
Edgewater	Industrial	2	2	$304,000	$304,000	$608,000
Edgewater	Mixed Use	10	16	$11,148,577	$11,148,577	$22,297,154
Edgewater	Residential	1,411	1,697	$371,406,665	$185,703,333	$557,109,998
Edgewater	Total	1,480	1,807	$442,322,263	$256,618,931	$698,941,194
Golden	Agriculture	1	1	$35,437	$35,437	$70,874
Golden	Commercial	277	377	$530,314,287	$530,314,287	$1,060,628,574
Golden	Exempt	61	126	$331,145,437	$331,145,437	$662,290,874
Golden	Industrial	171	189	$288,997,711	$288,997,711	$577,995,422
Golden	Mixed Use	111	128	$127,869,228	$127,869,228	$255,738,456
Golden	Residential	5,245	6,134	$2,303,042,937	$1,151,521,469	$3,454,564,406

Jurisdiction	Property Type	Improved Parcels	Building Count	Improved Value	Content Value	Total Value
	Total	5,866	6,955	$3,581,405,037	$2,429,883,569	$6,011,288,606
Lakeside	Commercial	13	26	$22,234,756	$22,234,756	$44,469,512
Lakeside	Mixed Use	1	1	$6,355,034	$6,355,034	$12,710,068
Lakeside	Total	14	27	$28,589,790	$28,589,790	$57,179,580
Lakewood	Agriculture	1	1	$46,378	$46,378	$92,756
Lakewood	Commercial	1,235	2,115	$2,012,874,841	$2,012,874,841	$4,025,749,682
Lakewood	Exempt	159	229	$412,727,409	$412,727,409	$825,454,818
Lakewood	Industrial	165	269	$179,504,955	$179,504,955	$359,009,910
Lakewood	Mixed Use	301	365	$249,172,992	$249,172,992	$498,345,984
Lakewood	Residential	47,529	51,150	$15,722,715,358	$7,861,357,679	$23,584,073,037
Lakewood	Total	49,390	54,129	$18,577,041,933	$10,715,684,254	$29,292,726,187
Littleton*	Commercial	2	2	$3,201,717	$3,201,717	$6,403,434
Littleton*	Exempt	1	1	$1,565,994	$1,565,994	$3,131,988
Littleton*	Residential	800	800	$347,633,125	$347,633,125	$695,266,250
Littleton*	Total	803	803	$352,400,836	$352,400,836	$704,801,672
Morrison	Commercial	20	36	$6,526,206	$6,526,206	$13,052,412
Morrison	Exempt	6	6	$9,920,151	$9,920,151	$19,840,302
Morrison	Industrial	2	2	$482,576	$482,576	$965,152
Morrison	Mixed Use	8	9	$2,197,352	$2,197,352	$4,394,704
Morrison	Residential	119	135	$46,271,710	$23,135,855	$69,407,565
Morrison	Total	155	188	$65,397,995	$42,262,140	$107,660,135
Mountain View	Commercial	16	28	$6,507,708	$6,507,708	$13,015,416
Mountain View	Exempt	2	2	$359,593	$359,593	$719,186
Mountain View	Mixed Use	2	2	$504,171	$504,171	$1,008,342
Mountain View	Residential	226	241	$39,517,346	$19,758,673	$59,276,019
Mountain View	Total	246	273	$46,888,818	$27,130,145	$74,018,963
Westminster*	Commercial	195	402	$381,774,297	$381,774,297	$763,548,594
Westminster*	Exempt	24	26	$104,426,475	$104,426,475	$208,852,950
Westminster*	Industrial	77	127	$124,568,101	$124,568,101	$249,136,202
Westminster*	Mixed Use	45	46	$370,810,142	$370,810,142	$741,620,284
Westminster*	Residential	14,709	15,090	$4,811,906,576	$2,405,953,288	$7,217,859,864
Westminster*	Total	15,050	15,691	$5,793,485,591	$3,387,532,303	$9,181,017,894
Wheat Ridge	Agriculture	2	2	$22,618	$22,618	$45,236
Wheat Ridge	Commercial	414	723	$416,007,224	$416,007,224	$832,014,448
Wheat Ridge	Exempt	59	76	$114,136,176	$114,136,176	$228,272,352
Wheat Ridge	Industrial	279	391	$214,853,118	$214,853,118	$429,706,236
Wheat Ridge	Mixed Use	134	172	$57,727,100	$57,727,100	$115,454,200
Wheat Ridge	Residential	10,277	12,141	$2,832,819,972	$1,416,409,986	$4,249,229,958
Wheat Ridge	Total	11,165	13,505	$3,635,566,208	$2,219,156,222	$5,854,722,430
Unincorporated	Agriculture	67	70	$7,972,025	$7,972,025	$15,944,050
Unincorporated	Commercial	907	1,480	$1,311,289,870	$1,311,289,870	$2,622,579,740

Jurisdiction	Property Type	Improved Parcels	Building Count	Improved Value	Content Value	Total Value
	Exempt	247	310	$453,766,591	$453,766,591	$907,533,182
	Industrial	612	777	$289,775,043	$289,775,043	$579,550,086
	Mixed Use	296	320	$237,060,925	$237,060,925	$474,121,850
	Residential	74,091	76,455	$27,306,605,653	$13,653,302,827	$40,959,908,480
	Total	76,220	79,412	$29,606,470,107	$15,953,167,281	$45,559,637,388
Grand Total	Grand Total	202,506	216,882	$76,441,573,052	$43,278,819,451	$119,720,392,503

Source: Jefferson County Assessor 2020, FEMA HAZUS * Only includes the portion within Jefferson County.

Critical Facilities, Infrastructure, and Other Important Community Assets

For the purposes of this plan, a critical facility is defined as one that is essential in providing utility or direction either during the response to an emergency or during the recovery operation. FEMA sorts critical facilities into seven lifeline categories as shown in

Figure 4-1 Lifeline Categories

These lifeline categories standardize the classification of critical facilities and infrastructure that provide indispensable service, operation, or function to a community. A lifeline is defined as providing indispensable service that enables the continuous operation of critical business and government functions, and is critical to human health and safety, or economic security. These categorizations are particularly useful as they:

Enable effort consolidations between government and other organizations (e.g. infrastructure owners and operators).

Enable integration of preparedness efforts among plans; easier identification of unmet critical facility needs.

Refine sources and products to enhance awareness, capability gaps, and progress towards stabilization.

Enhance communication amongst critical entities, while enabling complex interdependencies between government assets.

Highlight lifeline related priority areas regarding general operations as well as response efforts.

To develop a comprehensive list of critical facilities in Jefferson County (), two data sources were compiled and broken down along the aforementioned critical asset categories: Jefferson County’s GIS databases of critical facilities and infrastructure and the 2020 Homeland Infrastructure Foundation- Level Data (HIFLD) data.

The best available data was used, but some limitations include lack of complete or comprehensive data and values such as replacement costs. These databases were used in vulnerability assessments for hazards such as wildfire and flood, and are represented in maps and tables in the vulnerability by hazard section that follows.

Table 4-7 Summary of Critical Facilities by Jurisdiction and Lifeline

Jurisdiction	Communications	Energy	Food, Water, Shelter	Hazardous Material	Health and Medical	Safety and Security	Transportation	Total
Arvada	93	8	-	15	42	51	80	289
Edgewater	4	-	1	-	1	7	1	14
Golden	76	2	2	24	4	26	19	153
Lakewood	216	10	8	24	66	85	47	456
Morrison	8	-	-	3	1	2	8	22
Wheat Ridge	68	1	-	11	24	22	35	161
Unincorporated	705	23	24	51	48	135	267	1253
Total	1,170	44	35	128	186	328	457	2,348

Source: HIFLD and CERC

A 2020 Federal Highway Administration report found 22 bridges in Jefferson County in poor condition and in need of repairs. An additional 259 were found to be in fair condition, with only 166 being in good condition.

Maps of critical facilities in Jefferson County can be found in Appendix H (not for public release).

Natural, Historic, and Cultural Resources

Assessing the vulnerability of Jefferson County to different disasters also involves inventorying the natural, historical, and cultural assets of the area. This step is important for the following reasons:

The community may decide that these types of resources warrant a greater degree of protection due to their unique and irreplaceable nature and contribution to the overall economy.

If these resources are impacted by a disaster, knowing so ahead of time allows for more prudent care in the immediate aftermath, when the potential for additional impacts are higher.

The rules for reconstruction, restoration, rehabilitation, and/or replacement are often different for these types of designated resources.

Natural resources can have beneficial functions that reduce the impacts of natural hazards, such as wetlands and riparian habitat, which help absorb and attenuate floodwaters.

Natural Resources

Natural resources are important to include in benefit-cost analyses for future projects, and may be used to leverage additional funding for projects that also contribute to community goals for protecting sensitive natural resources. Awareness of natural assets can lead to opportunities for meeting multiple objectives. For instance, protecting wetlands areas protects sensitive habitat as well as attenuates and stores floodwaters.

Jefferson County contains a unique combination of prairie, forest, and tundra environments. The HMPC recognizes three types of valuable natural resources worthy of protection: environmental conservation areas, natural landmarks, and natural areas. These areas are described below and mapped in

Environmental conservation areas are so designated because of the value they provide in the perpetuation of those species, biological communities, and ecological processes that function over large geographic areas and require a high degree of naturalness.

Natural landmarks are defined as prominent landscape features that distinguish a specific locality in Jefferson County and are important because of the views they afford, their value as scenic vistas and backdrops, and the intrinsic value they hold as wildlife or plant habitats, natural areas, park and open space preserves, and open land areas.

Natural areas are physical or biological areas that either retain or have reestablished their natural characters, although they need not be completely undisturbed, and that typify native vegetation and associated biological and geological features or provide habitat for rare or endangered animal or plant species or include geologic or other natural features of scientific or educational value.

Figure 4-2 Jefferson County Public Lands

PIKE NATIONAL FOREST TO SOUTH

Wetlands

Wetlands are a valuable natural resource for communities, due to their benefits to water quality, wildlife protection, recreation, and education. Wetlands also play an important role in hazard mitigation by reducing flood peaks and slowly releasing floodwaters to downstream areas. When surface runoff is dampened, the erosive powers of the water are greatly diminished. Furthermore, the reduction in the velocity of inflowing water as it passes through a wetland helps remove sediment being transported by the water. They also provide drought relief in water-scarce areas where the relationship between water storage and streamflow regulation are vital.

Jefferson County has numerous freshwater lakes and freshwater emergent wetlands in the various creeks and ditches scattered throughout the northeast (mostly urbanized) part of the County. These areas provide critical habitat as well as help mitigate flooding.

Endangered Species and Imperiled Natural Plant Communities

To further understand natural resources that may be particularly vulnerable to a hazard event, as well as those that need consideration when implementing mitigation activities, it is important to identify at-risk species (i.e., endangered species) in the planning area. An endangered species is any species of fish, plant life, or wildlife that is in danger of extinction throughout all or most of its range. A threatened species is a species that is likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range. Both endangered and threatened species are protected by law and any future hazard mitigation projects are subject to these laws. Candidate species are plants and animals that have been proposed as endangered or threatened but are not currently listed. Species listed as resolved taxon have received a finding of Not Warranted or Not Substantial or have been removed from the candidate list.

According to the U.S. Fish and Wildlife Service (FWS), as of February 2021, there were 27 federal endangered, threatened, or candidate species that may be present Jefferson County. These species are listed in Note that the FWS is based on the existence of potential habitat for the species, and not all listed species may actually be present in the County.

Table 4-8 Threatened, Endangered, or other Listed Species Potentially Found in Jefferson County

Type of Species	Common Name	Scientific Name	Status
Amphibians	Northern leopard frog	Rana pipiens	Resolved Taxon
Birds	Whooping crane	Grus americana)	Experimental Population, Non-Essential
Birds	Bald eagle	Haliaeetus leucocephalus	Recovery
Birds	American peregrine falcon	Falco peregrinus anatum	Recovery
Birds	Southern white-tailed ptarmigan	Lagopus leucura altipetens	Resolved Taxon
Birds	Swainson’s hawk	Buteo swainsoni	Resolved Taxon
Birds	Ferruginous hawk	Buteo regalis	Resolved Taxon
Birds	White-faced ibis	Plegadis chihi	Species of Concern
Birds	Western burrowing owl	Athene cunicularia ssp. hypugaea	Species of Concern
Birds	Mexican spotted owl	Strix occidentalis lucida	Threatened
Flowering Plants	Colorado Butterfly plant	Gaura neomexicana var. coloradensis	Recovery
Flowering Plants	Bell’s Twinpod	Physaria bellii	Species of Concern
Flowering Plants	Ute ladies’-tresses	Spiranthes diluvialis	Threatened
Flowering Plants	Western prairie fringed Orchid	Platanthera praeclara	Threatened

Type of Species	Common Name	Scientific Name	Status
Insects	Pawnee montane skipper	Hesperia leonardus montana	Threatened
Mammals	Swift fox	Vulpes velox	Resolved Taxon
Mammals	Black-tailed prairie dog	Cynomys ludovicianus	Resolved Taxon
Mammals	Gunnison’s prairie dog	Cynomys gunnisoni	Resolved Taxon
Mammals	North American wolverine	Gulo gulo luscus	Resolved Taxon
Mammals	American pika	Ochotona princeps	Resolved Taxon
Mammals	Fringed myotis	Myotis thysanodes	Species of Concern
Mammals	Long-legged myotis	Myotis volans	Species of Concern
Mammals	Long-eared myotis	Myotis evotis	Species of Concern
Mammals	Preble’s meadow jumping mouse	Zapus hudsonius preblei	Threatened
Mammals	Canada Lynx	Lynx canadensis	Threatened
Mammals	Little brown bat	Myotis lucifugus	Under Review
Reptiles	Eastern short-horned lizard	Phrynosoma douglassii brevirostra	Species of Concern

Source: U.S. Fish & Wildlife Service

Historic and Cultural Resources

Information about historic assets in Jefferson County came from local sources, as well as two historic inventories:

The National Register of Historic Places is the Nation’s official list of cultural resources worthy of preservation. The National Register is part of a national program to coordinate and support public and private efforts to identify, evaluate, and protect historic and archeological resources. Properties listed include districts, sites, buildings, structures, and objects that are significant in American history, architecture, archaeology, engineering, and culture. The National Register is administered by the National Park Service, which is part of the U.S. Department of the Interior.

The Colorado State Register of Historic Properties is a listing of the state’s significant cultural resources worthy of preservation for the future education and enjoyment of Colorado’s residents and visitors.

Properties listed in the Colorado State Register include individual buildings, structures, objects, districts, and historic and archaeological sites. The Colorado State Register program is administered by the Office of Archaeology and Historic Preservation within the Colorado Historical Society. Properties listed in the National Register of Historic Places are automatically placed in the Colorado State Register.

lists the 113 properties and districts in Jefferson County that are on the National Register of Historic Places and/or the Colorado State Register of Historic Properties.

Table 4-9 Jefferson County Historic Properties in National & State Registers

Property Name	City	Register	Listed Date
Arvada Downtown	Arvada	National	7/15/1998
Arvada Flour Mill	Arvada	National	4/24/1975
Churches Ranch	Arvada	National	7/23/1998
Enterprise Grange No. 15	Arvada	State	8/11/1999
Ralston Cemetery	Arvada	State	6/30/2011
Ralston Gold Discovery Site (Gold Strike Park)	Arvada	State	12/13/1995
Reno Park Addition Historic District	Arvada	National	9/29/1999
Russell-Graves House	Arvada	National	5/9/1983

Property Name	City	Register	Listed Date
Seventh Day Adventist Church – Arvada Jaycee Hall	Arvada	State	2/24/2011
Stocke—Walter Addition Historic District	Arvada	National	9/24/1999
Silver Spruce Ranch	Bailey	State	6/12/1996
Blue Jay Inn	Buffalo Creek	National	10/1/1974
Green Mercantile Store	Buffalo Creek	National	10/1/1974
Green Mountain Ranch	Buffalo Creek	National	10/1/1974
La Hacienda	Buffalo Creek	National	7/20/1973
Bradford Junction	Conifer	State	1/23/2014
Conifer Junction Schoolhouse	Conifer	National	2/10/2014
Midway House	Conifer	National	9/18/1990
Pleasant Park School	Conifer	State	6/12/1996
Tower of Memories	Denver	National	9/25/1987
Bergen Park	Evergreen	National	11/15/1990
Bergen Park Church	Evergreen	State	6/1/2018
Brook Forest Inn	Evergreen	National	7/29/2009
Corwina Park, O’Fallon Park, Pence Park	Evergreen	National	12/28/1990
Dedisse Park	Evergreen	National	11/15/1990
Evergreen Conference District	Evergreen	National	5/1/1979
Everhardt Ranch	Evergreen	National	5/7/1980
Fillius Park	Evergreen	National	2/24/1995
Hiwan Homestead	Evergreen	National	4/9/1974
Humphrey House	Evergreen	National	12/31/1974
Ammunition Igloo	Golden	National	5/20/1993
Astor House Hotel	Golden	National	3/1/1973
Barnes—Peery House	Golden	National	10/12/2001
Calvary Episcopal Church	Golden	National	3/3/1995
Camp George West Historic District	Golden	National	2/11/1993
Colorado Amphitheater	Golden	National	5/20/1993
Colorado Midland Railway Observation Car No. 111	Golden	State	12/11/1996
Colorado National Guard Armory	Golden	National	12/18/1978
Colorow Point Park	Golden	National	11/15/1990
Coors, Herman, House	Golden	National	10/17/1997
Deaton Sculptured House	Golden	National	2/24/2004
Denver & Rio Grande Railroad Cars (13 entries)	Golden	State	various
Denver and Rio Grande Western Railroad Caboose No. 0578	Golden	National	11/4/2003
First Presbyterian Church of Golden—Unger House	Golden	National	3/14/1991
Genesee Park	Golden	National	11/15/1990
Golden Cemetery	Golden	National	4/18/2012
Golden High School	Golden	National	3/14/1997
Golden Welcome Arch	Golden	State	6/14/2000
Great Western Railway Combine No. 100	Golden	State	9/11/1996

Property Name	City	Register	Listed Date
Lariat Trail Scenic Mountain Drive	Golden	National	11/15/1990
Lookout Mountain Park	Golden	National	11/15/1990
Lorraine Lodge	Golden	National	1/18/1984
Loveland Building and Coors Building	Golden	National	5/16/1996
Magic Mountain Site	Golden	National	8/21/1980
Mount Vernon House	Golden	National	11/20/1970
Oscar Barber House	Golden	State	6/13/1994
Quaintance Block	Golden	National	3/25/1994
Queen of Heaven Orphanage Summer Camp	Golden	National	1/14/2000
Rio Grande Southern Railroad Cars (4 entries)	Golden	State	various
Rio Grande Southern Railroad Engine No. 20	Golden	National	12/14/2000
Rio Grande Southern Railroad, Motor No. 2	Golden	National	2/14/1997
Rio Grande Southern Railroad, Motor No. 6	Golden	National	2/19/1997
Rio Grande Southern Railroad, Motor No. 7	Golden	National	2/28/1997
Rockland Community Church and Cemetery	Golden	National	8/5/2009
Rocky Flats Plant	Golden	National	5/19/1997
Romano, Samuel and Albina, House	Golden	National	9/26/2016
Rooney Ranch	Golden	National	2/13/1975
Tallman Ranch	Golden	State	6/14/1995
Thiede Ranch	Golden	National	1/11/1996
Twelfth Street Historic Residential District	Golden	National	9/22/1983
Little Park	Idledale	National	2/24/1995
Starbuck Park	Idledale	National	6/30/1995
Indian Hills Community Hall & Firehouse	Indian Hills	State	5/14/1997
Bonfils-Stanton Belmar Estate Outbuildings	Lakewood	State	5/23/2013
Building 710, Defense Civil Preparedness Agency, Region 6 Operations Center	Lakewood	National	3/2/2000
Country Club Garden Apartments	Lakewood	State	8/27/2009
Davies’ Chuck Wagon Diner	Lakewood	National	7/2/1997
Denver and Intermountain Railroad Interurban No. 25	Lakewood	National	1/12/2012
Hill Section, Golden Hill Cemetery	Lakewood	National	7/31/1995
Howell House	Lakewood	State	9/11/1996
Jewish Consumptives’’ Relief Society	Lakewood	National	6/26/1980
Office of Civil Defense Emergency Operations Center	Lakewood	National	12/16/1999
Peterson House	Lakewood	National	9/10/1981
Schnell Farm	Lakewood	National	2/14/1997
South Ranch	Lakewood	National	4/18/2003
Stone House	Lakewood	National	5/1/1975
Washington Heights School	Lakewood	State	6/13/1994
Bradford House II	Littleton	National	2/2/2001
Bradford-Perley House	Littleton	State	2/2/2015
Hildebrande Ranch	Littleton	National	3/13/1975

Property Name	City	Register	Listed Date
Shaffer, John C., Barn	Littleton	National	7/12/2019
Bear Creek Canyon Scenic Mountain Drive	Morrison	National	11/15/1990
Bradford House III Archeological Site	Morrison	National	4/8/1980
Bradford, Robert Boyles, Property	Morrison	National	2/2/2015
Craig, Katherine, Park	Morrison	National	6/30/1995
Dinosaur Ridge	Morrison	State	3/10/1993
District No. 17 – Medlen School	Morrison	State	4/14/2015
District No. 17 School—Medlen School	Morrison	National	4/14/2015
Fort, The	Morrison	National	7/14/2006
LoDaisKa Site	Morrison	National	9/25/2003
Morrison Historic District	Morrison	National	9/28/1976
Morrison Schoolhouse	Morrison	National	9/4/1974
Red Rocks Park District	Morrison	National	5/18/1990
Baehr Lodge / Baehr Den of the Rockies (Pine Valley Lodge)	Pine	State	6/10/1998
Staunton Ranch Rural Historic Landscape	Pine	National	12/4/2012
North Fork Historic District	Pine and South Platte	National	10/9/1974
North Fork Historic District (Boundary Increase)	Pine and South Platte	National	10/8/2008
Baugh, James H., House	Wheat Ridge	National	8/14/2012
Crown Hill Burial Park	Wheat Ridge	National	7/24/2008
Fruitdale Grade School	Wheat Ridge	National	3/20/2013
Pioneer Sod House	Wheat Ridge	National	3/14/1973
Richards Mansion	Wheat Ridge	National	9/15/1977
Wheat Ridge Post Office	Wheat Ridge	State	8/12/1992

Sources: National Register of Historic Places, and Colorado State Register of Historic Properties:

It should be noted that as defined by the National Environmental Policy Act (NEPA), any property over 50 years of age is considered a historic resource and is potentially eligible for the National Register. Thus, in the event that the property is to be altered, or has been altered, as the result of a major federal action, the property must be evaluated under the guidelines set forth by NEPA. Structural mitigation projects are considered alterations for the purpose of this regulation.

Economic Assets

Economic assets at risk may include major employers or primary economic sectors, such as agriculture, whose losses or inoperability would have severe impacts on the community and its ability to recover from disaster. After a disaster, economic vitality is the engine that drives recovery. Every community has a specific set of economic drivers, which are important to understand when planning ahead to reduce disaster impacts to the economy. When major employers are unable to return to normal operations, impacts ripple throughout the community. A list of the top employers in Jefferson County by number of employees can be found in Section 2.

Growth and Development Trends

A key strategy for reducing future losses in a community is to avoid development in known hazard areas while enforcing the development of safe structures in other areas. The purpose of this strategy is to keep people, businesses, and buildings out of harm’s way before a hazard event occurs. The 2021 Jefferson County Hazard Mitigation Plan highlights areas where future development can be expected and areas

where mitigation options can be considered in future land use decisions to ensure safe, smart growth in the county.

Figure 4-3 Jefferson County Community Plan Areas

Source: Jefferson County, JEFFCO demographics,

Jefferson County has grown significantly in the past decade and is one of the fastest growing counties in the State. Between 2000 and 2019 Jefferson County’s total population increased by 10.7% (DOLA 2021). The amount of growth that County has seen over the past twenty years has been dictated by the availability of undeveloped land. Based on observed population growth trends, housing demand within Jefferson County is expected to remain steady over the next decade.

Land use patterns and cover varies across the County. Approximately 40% of the land in unincorporated Jefferson County is protected by the Jefferson County Open Space Division (Jefferson County 2018). In addition to the Jefferson County Comprehensive Master Plan, which helps guide development in the County, there are also eight Area Plans (North Plains, Central Plains, South Plains, North Mountains, Central Mountains, Indian Hills, Evergreen Area and Conifer/285 Corridor Area) that provide land use recommendations for each of these unique areas in Jefferson County. While most of the total land area (72%) in County is located in the Mountains Areas, most development in the County between 2010 and 2018 has taken place in the South Plains Areas (Jefferson County 2019). shows the location and general size of each Area Plan in the county.

Hazard Profiles

The hazards identified in Section 4.1: Hazard Identification are profiled individually in this section. Much of the profile information came from the same sources used to initially identify the hazards.

Profile Methodology

Each hazard is profiled in a similar format that is described below. It is important to note that the profiles are data driven, and that potential errors or omissions may exist in the data. In particular, there is a time variance between the different data sets. For example, winter storms have been tracked in the planning area for a longer period of time than swelling soils hazards have been documented, so the comparison of severity, previous occurrences, and rates of future occurrences between the two hazards is somewhat skewed. This variance exists between all known hazards in this plan. The information presented is for planning level assessments only.

Description

This subsection gives a generic description of the hazard and associated problems, followed by details on the hazard specific to Jefferson County.

Geographic Extent

This subsection discusses how extensive the hazard is expected to be relative to Jefferson County. It may also include specific discussions regarding which areas of the County are most likely to be affected by the profiled hazard. An extent rating is assigned based on the following methodology:

Negligible: Less than 10 percent of planning area or isolated single-point occurrences

Limited: 10 to 25 percent of the planning area or limited single-point occurrences

Significant: 25 to 75 percent of planning area or frequent single-point occurrences

Extensive: 75 to 100 percent of planning area or consistent single-point occurrences

Percent of planning area is calculated by comparing the amount of area affected to the total county area: (affected acres/total county acres) * 100 = percent of affected planning area. Single point events, such as lightning, are evaluated for geographic extent by examining the density of the events collectively.

Previous Occurrences

This subsection contains an overview history of the hazard’s occurrences, compiled from multiple data sources. This includes information provided by the HMPC. Significant or historic incidents are profiled in greater detail and include scope, severity, and magnitude, and known impacts.

Probability of Future Occurrences

This subsection utilizes the frequency of past (known) events to calculate a probability of future occurrences. The likelihood is categorized into four different classifications:

Unlikely: Less than 1 percent probability of occurrence in the next year, or has a recurrence interval of greater than every 100 years.

Occasional: Between a 1 and 10 percent probability of occurrence in the next year, or has a recurrence interval of 11 to 100 years.

Likely: Between 10 and 90 percent probability of occurrence in the next year, or has a recurrence interval of 1 to 10 years

Highly Likely: Between 90 and 100 percent probability of occurrence in the next year, or has a recurrence interval of less than 1 year.

Each hazard is calculated for a probability of future occurrence by comparing the known number of events to the available historic record: (# of known events/years on historic record) * 100 = Probability of Future Occurrence. Stated mathematically, the methodology for calculating the probability of future occurrences is:

# of known events
years of historic record	x100

This formula evaluates that the probability of a given hazard occurring in any given year in Jefferson County. The period of record will vary for each hazard and is based upon available data. In some instances, additional prediction methods are also measured by recurrence intervals, such as floods or hazards where the events occur more than once a year.

Magnitude and Severity

This subsection summarizes the anticipated magnitude and severity of a hazard event based largely on previous occurrences and specific aspects of risk as it relates to the planning area. Magnitude and Severity are classified in the following manner:

Negligible: Less than 10 percent of property is severely damaged, facilities and services are unavailable for less than 24 hours, injuries and illnesses are treatable with first aid or within the response capability of the jurisdiction.

Limited: 10 to 25 percent of property is severely damaged, facilities and services are unavailable for between 1 and 7 days, injuries and illnesses require sophisticated medical support that does not strain the response capability of the jurisdiction, or results in very few permanent disabilities.

Critical: 25 to 50 percent of property is severely damaged, facilities and services are unavailable or severely hindered for 1 to 2 weeks, injuries and illnesses overwhelm medical support for a brief period of time, or result in many permanent disabilities and a few deaths.

Catastrophic: More than 50 percent of property is severely damaged, facilities and services are unavailable or hindered for more than 2 weeks, the medical response system is overwhelmed for an extended period of time or many deaths occur.

The rating is calculated by evaluating the event of record against these criteria. Since most events incur different levels of severity for each element, the rating is assigned to the classification with the most documented occurrences. The purpose of a magnitude and severity rating is to establish the highest known potential threshold of an event to help guide the mitigation goals and actions development. If there are significant events with much lower magnitude and severity ratings than the event of record, this discrepancy will be noted.

Climate Change Considerations

Climate includes patterns of temperature, precipitation, humidity, wind and seasons. Climate plays a fundamental role in shaping natural ecosystems, and the human economies and cultures that depend on them. “Climate change” refers to changes over a long period of time. It is generally perceived that climate change has had and will continue to have measurable impacts on the occurrence and severity of natural hazards around the world. Impacts include the following:

Snow cover losses will continue, and declining snowpack will continue to affect snow-dependent water supplies and stream flow levels around the world.

The risk of drought and the frequency, intensity, and duration of heat waves are expected to continue to increase.

More extreme precipitation events will continue to be likely, increasing the risk of flooding.

The Earth’s average temperature is expected to continue to increase.

In 2018, the U.S. Global Change Research Program released the Fourth National Climate Assessment (NCA4), the authoritative and comprehensive report on climate change and its impacts in the United States. Not only did the report confirm that climate induced hazards continues to affect Americans in every region of the U.S., the report identifies increased heat, drought, insect outbreaks, wildfire, and flooding as key climate-related concerns for the Southwest region of the U.S., which includes Colorado. The following is a summary of climate change impacts from the Fourth National Climate Assessment.

Recent warming in the southwest region is among the most rapid in the nation and is significantly greater than the global average, and the period since 1950 has been hotter than any comparable long period in at least 600 years. Summer temperatures across the state are expected to warm more than winter temperatures and projections suggest that typical summer months will be as warm as (or warmer than) the hottest 10% of summers that occurred between 1950 and 1999. Under the higher emissions scenario (RCP8.5) climate models predict an increase of 8.6°F in the southwest regional annual average temperature by 2100.

Projected increases in temperatures in the southwest region are also projected to increase probabilities of natural events such as wildfires, drought, and extreme precipitation. These temperature changes have great potential to directly affect public health through increased risk of heat stress and infrastructure through increased risk of disruptions of electric power generation. Water supplies are also vulnerable to impacts of higher temperatures. While water supplies generally change year-to-year due to variabilities in water use and precipitation, higher temperatures are projected to increase evapotranspiration, reducing the effectiveness of precipitation in replenishing surface water and soil moisture. This will have direct impacts on crop yields and productivity of key regional crops and livestock a major risk for the agricultural industry and food security nationwide.

The impacts of climate induced hazards already pose a threat to people and property in the southwest region of the United States, including Jefferson County. Vulnerable populations, in particular those who are low-income, children, elderly, disabled and minorities will likely be impacted by the effects of climate induced hazards disproportionately than other populations (Refer to Section 2 for more information on social vulnerability in the county). Together, these impacts represent a slow-onset disaster that is likely to manifest and change over time. Current projections predict even more rapid changes in the near future, which are likely to affect many of the natural hazards that Jefferson County has historically dealt with.

According to HMPC the County is already experiencing some hazards with more frequency and intensity than in years past, such as drought, flooding, wildfire and extreme heat.

Jefferson County’s two most frequent and devastating hazards are wildfire and flood, both of which are expected to be impacted by our changing climate. The nature of erosion and public health hazards are also likely to evolve in intensity and character due to a changing regional climate. For these reasons, the hazard identification and risk assessment for the 2021 Jefferson County Hazard Mitigation Plan update includes climate change considerations discussion on how climate change may impact the frequency, intensity, and distribution of specific hazards within the county. Because many impacts of climate induced hazards cross county boundaries, some of the discussion looks at impacts on a regional scale. As climate science evolves, future mitigation plan updates may consider including climate change projections in the risk rankings and vulnerability assessments of the hazards included in the Plan.

Vulnerability Assessment

With Jefferson County’s hazards identified and profiled, the HMPC conducted a vulnerability assessment to describe the impact that the significant hazards would have on the County. The vulnerability assessment quantifies, to the extent feasible, assets at risk to natural hazards and estimates potential losses. This vulnerability assessment followed the methodology described in the FEMA publication Understanding Your Risks—Identifying Hazards and Estimating Losses, as well as Tasks 5 and 6 of the 2013 FEMA Local Mitigation Planning Handbook. The vulnerability assessment first describes the total vulnerability and values at risk and then discusses vulnerability by hazard.

The vulnerability assessment was conducted based on the significance of the hazard utilizing best available data. This assessment is an attempt to quantify assets at risk, by jurisdiction where possible, to further define populations, buildings, and infrastructure at risk to natural hazards. The methods of analysis vary by hazard type and data available and are discussed further in 4.3.4 with each hazard analyzed. The information presented is for planning level assessments only. Avalanche is omitted from this vulnerability assessment due to the relatively low significance, lack of previous damages based on research, and a lack of data to support quantifying future losses. Data to support the vulnerability assessment was collected and compiled from the following sources:

Current County and municipal GIS data (hazards, base layers, critical facilities and assessor’s data)

2010 US Census, 2019 American Community Survey, and 2019 CO Department of Local Affairs (DOLA) data

2020 Homeland Infrastructure Foundation-Level Data (HIFLD) data

Written descriptions of inventory and risks provided by participating jurisdictions;

A refined flood loss estimation by jurisdiction with the use of geospatial analysis for both 1% and 0.2% annual chance flooding

Updated modeling of earthquake loss potential with HAZUS-MH 2.2, including a 2,500 year probabilistic scenario and a hypothetical M 6.5 event on the Golden Fault

Existing plans and studies, and applicable regulations

Personal interviews with planning team members, hazard experts, and County and municipal staff.

The scope of the vulnerability assessment is to describe the risks to the County as a whole. The vulnerability assessment first describes the assets in Jefferson County, including the total exposure of people and property; critical facilities and infrastructure; natural, historic, and cultural resources; and economic assets. Development trends, including population growth and land status, are analyzed in relation to hazard-prone areas. Next, where data was available, hazards are evaluated in more detail and potential losses are estimated. Data from each jurisdiction was also evaluated and is integrated here but specific variations of risk are noted in the appropriate annex. The methods to assess vulnerability presented here include an updated analysis from the 2016 Jefferson County Multi-Hazard Mitigation Plan. This includes a detailed risk assessment for all hazards based on advanced methods and updated hazard and inventory data. Thus this 2021 plan should be considered the baseline for measuring changes in vulnerability during future updates, recognizing that vulnerability information should become more refined as data sources and methodologies improve over time. Examples of refinements and changes made in this plan include:

Updated population and building inventory information, including most recent values and 2020 assessor data;

An updated and more comprehensive inventory of critical facilities;

An updated inventory of natural, historic, and cultural resources;

A refined flood loss estimation by jurisdiction with the use of geospatial data provided by the Assessor’s office and FEMA NFHL to perform GIS analysis for both 1% and 0.2% annual chance flooding, supplemented by local flood payers;

Updated modeling of earthquake loss potential with HAZUS-MH 2.2, including a 2,500 year probabilistic scenario M7.25 and a hypothetical M 6.5 event on the Golden Fault;

Detailed inventory by jurisdiction of potential structures and critical facilities at risk to hazards

Overall Hazard Significance

Overall potential impact of each hazard is summarized in this subsection, based on geographic extent, probability of future occurrences, and the magnitude and severity of the event of record. These ratings are averaged to provide an overall hazard significance rating, which is useful for comparing the hazards to one another and for guiding the development of actions and priorities. The overall hazard significance ratings are classified as follows:

Low: Two or more of the criteria fall in the lower classifications, or the event has a minimal impact on the planning area. This rating is also sometimes used for hazards with a minimal or unknown record of occurrences and impacts or for hazards with minimal mitigation potential.

Medium: The criteria fall mostly in the middle ranges of classifications, and the event’s impacts on the planning area are noticeable but not devastating. This rating is also sometimes utilized for hazards with a high impact rating but an extremely low occurrence rating.

High: The criteria consistently fall along the high ranges of the classification and the event exerts significant and frequent impacts on the planning area. This rating is also sometimes utilized for hazards with a high psychological impact or for hazards that the jurisdiction identifies as particularly relevant.