Requirement Section 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.
Risk to natural hazards is a combination of hazard, vulnerability,
and capability. The risk assessment process identifies and profiles
relevant hazards and assesses the exposure of lives, property, and
infrastructure to these hazards. The goal of the risk assessment is
to estimate the potential loss in Mesa County, including loss of life,
personal injury, property damage, and economic loss, from a hazard
event. The risk assessment process allows communities in Mesa County
to better understand their potential risk to natural hazards and provides
a framework for developing and prioritizing mitigation actions to
reduce risk from future hazard events.
The risk assessment for Mesa County and its jurisdictions followed
the methodology described in the FEMA publication Local Mitigation
Planning Handbook (2013), which includes a four-step process:
(d) Estimate losses.
This article is divided into three parts: hazard identification,
hazard profiles, and vulnerability assessments.
|
(Res. 61-20, 10-7-20; Res. 32-15, 7-1-15; Res. 05-10, 1-6-10)
Requirement Section 201.6(c)(2)(i): [The risk assessment
shall include a] description of the type … of all natural hazards
that can affect the jurisdiction.
The Mesa County Hazard Mitigation Planning Committee (HMPC)
reviewed data and discussed the impacts of each of the hazards required
by FEMA for consideration, which are listed below, to determine the
hazards that threaten Mesa County and its jurisdictions:
Avalanche
|
Expansive Soils
|
Landslide
|
Windstorm
|
Coastal Erosion
|
Extreme Heat
|
Severe Winter Storm
|
|
Coastal Storm
|
Flood
|
Tornado
|
|
Dam/Levee Failure
|
Hailstorm
|
Tsunami
|
|
Drought
|
Hurricane
|
Volcano
|
|
Earthquake
|
Land Subsidence
|
Wildfire
|
|
Data on past impacts and future probability of these hazards
was collected from the following sources:
State of Colorado Natural Hazard Mitigation Plan (2018)
|
Mesa County Hazard Mitigation Plan (2015)
|
Spatial Hazard Event and Loss Database (SHELDUS), a component
of the University of South Carolina Hazards Research Lab
|
National Oceanic and Atmospheric Administration’s (NOAA)
National Climatic Data Center
|
Disaster declaration history from FEMA, the Public Entity Risk
Institute, and the U.S. Department of Agriculture (USDA) Farm Service
Agency
|
The HMPC eliminated some hazards from further analysis because
they do not occur in Mesa County or their impacts were not considered
significant in relation to other hazards. Table 5 lists these hazards
and the reasoning for their removal from consideration.
Table 5: Removed Hazards
|
---|
Hazard
|
Explanation for Removal from Plan
|
---|
Coastal Erosion
|
Mesa County is not near coastal area.
|
Coastal Storm
|
Mesa County is not near coastal area.
|
Hailstorm
|
Hailstorms occur, but large-sized damaging hail is rare. Past
damage has been negligible.
|
Hurricane
|
Mesa County is not near coastal area.
|
Tsunami
|
Mesa County is not near coastal area.
|
Volcano
|
Dotsero, near Glenwood Canyon, is the only volcano of concern
in Colorado. It has not erupted in 4,000 years.
|
The HMPC identified 13 natural hazards that could affect Mesa
County and other jurisdictions. These hazards are profiled in further
detail throughout this plan. Although not required by the Disaster
Mitigation Act of 2000, the HMPC decided to address one manmade hazard –
hazardous materials release. The risk from this hazard is related
primarily to the transportation of hazardous materials through the
County or from a release generated at any one of the number of facilities
that produces or stores chemicals on site.
(Res. 61-20, 10-7-20; Res. 32-15, 7-1-15; Res. 05-10, 1-6-10)
Mesa County has received the following disaster declarations:
Year
|
Type of Declaration
|
Hazard
|
---|
1984
|
Presidential
|
Flooding
|
1995
|
State
|
Flooding
|
2002
|
Presidential
|
Wildfires
|
2002
|
USDA Disaster
|
Drought
|
2006
|
USDA Disaster
|
Drought
|
2012
|
State
|
Wildfire
|
2012
|
USDA Disaster
|
Drought
|
2012
|
USDA Disaster
|
Crop
|
2013
|
USDA Disaster
|
Crop
|
2014
|
USDA Disaster
|
Drought
|
2014
|
USDA Disaster
|
Crop
|
2014
|
Local/State
|
Landslide
|
2015
|
USDA Disaster
|
Drought
|
2015
|
USDA Disaster
|
Severe Freeze
|
2017
|
USDA Disaster
|
Severe Freeze
|
2018
|
USDA Disaster
|
Drought
|
2019
|
USDA Disaster
|
Drought
|
2020
|
Local/State/Federal
|
Pandemic
|
(Res. 61-20, 10-7-20; Res. 32-15, 7-1-15; Res. 05-10, 1-6-10)
Requirement Section 201.6(c)(2)(i): [The risk assessment
shall include a] description of the … 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.
Requirement Section 201.6(c)(2)(ii): [The risk assessment
shall include a] description of the jurisdiction’s vulnerability
to the hazards described in paragraph (c)(2)(i) of this section. The
description shall include an overall summary of each hazard and its
impact on the community.
The hazards identified in this section are profiled individually
and a summary of the probability of future occurrence and potential
magnitude is provided. Each hazard was also given an overall rating
of High – Medium – Low based on the score it
received by using the following formula:
Total Score = Occurrences x Impacts (Occurrences
x [Geographic Location + Magnitude/Severity])
|
Detailed profiles for each of the identified hazards include
the following information:
(a) Hazard Description.
This section consists of a general
description of the hazard and the general impacts it may have on a
community.
(b) Geographic Location.
This section describes the geographic
extent or location of the hazard in the planning area and identifies
the affected area as isolated, small, medium, or large.
(1) Large (8) – Greater than 50 percent of the County affected.
(2) Medium (6) – 25 to 50 percent of the County affected.
(3) Small (4) – 10 to 25 percent of the County affected.
(4) Isolated (2) – Less than 10 percent of the County affected.
(c) Occurrence.
This section includes information on historic
incidents, including impacts and costs, if known. A historic incident
worksheet (worksheet #1) was used to capture the incident information
from participating jurisdictions.
(d) Future Occurrence.
The frequency of past events is used
to gauge the likelihood of future occurrences. Based on historical
data, the probability of future occurrence is categorized as follows
and given a corresponding score:
(1) Highly Likely: (8). Near 100 percent chance of occurrence next year
or happens every year.
(2) Likely: (6). Ten to 100 percent chance of occurrence in next year
or has a recurrence interval of 10 years or less.
(3) Occasional: (4). One to 10 percent chance of occurrence in the next
year or has a recurrence interval of 11 to 100 years.
(4) Unlikely: (2). Less than one percent chance of occurrence in next
100 years or has a recurrence interval of greater than every 100 years.
The probability, or chance of occurrence, was calculated where
possible based on existing data.
|
(e) Magnitude/Severity.
This section summarizes the magnitude/severity
or extent of hazard event in terms of deaths, injuries, property damage,
and interruption of essential facilities and services. Magnitude and
severity is classified in the following manner and given a corresponding
score:
(1) Catastrophic (8). Multiple deaths; property destroyed and severely
damaged; and/or interruption of essential facilities and service for
more than 72 hours.
(2) Critical (6). Isolated deaths and/or multiple injuries and illnesses;
major or long-term property damage that threatens structural stability;
and/or interruption of essential facilities and services for 24 to
72 hours.
(3) Limited (4). Minor injuries and illnesses; minimal property damage
that does not threaten structural stability; and/or interruption of
essential facilities and services for less than 24 hours.
(4) Negligible (2). No or few injuries or illnesses; minor quality of
life loss; little or no property damage; and/or brief interruption
of essential facilities or services.
(f) Impact of a Changing Climate.
According to the 2018
National Climate Assessment a changing climate would create new risks
and exacerbate existing vulnerabilities in communities across the
United States (U.S.), presenting growing challenges to human health
and safety, quality of life, and the rate of economic growth. This
could include more frequent and intense extreme weather and climate-related
events, as well as changes in average climate conditions, which could
continue to damage infrastructure, ecosystems, and social systems.
The U.S. Environmental Protection Agency (EPA) concludes that a world
of warmer temperatures could lead to less predictable weather patterns
and rising sea levels. While impacts within and across regions may
not be distributed equally, these and other impacts would threaten
the reliable delivery of many community services. Although extreme
weather events are caused by a variety of contributing factors, human-induced
climate change is considered by a large majority of the scientific
community to be one of those contributing factors.
The 2018 National Climate Assessment found that temperatures
increased across almost all of the Southwest U.S. from 1901 to 2016
with the greatest increases in southern California and western Colorado.
If this trend were to continue, the increase in heat and reduction
of snow under a changing climate would tend to increase the duration
and severity of droughts. Additionally, this could contribute to aridification
(a potentially permanent change to a drier environment) through lower
soil moisture, reduced snow cover and changes in the timing and efficiency
of snowmelt and runoff.
The 2018 National Climate Assessment also estimated that the
area burned by wildfire across the western U.S. from 1984 to 2015
was twice what would have been burned had the climate not been changing.
Some of the worst wildfires in Colorado State history have occurred
within the last 10 years, including the Black Forest Fire in 2013,
Spring Creek Fire in 2018, and the 416 Fire in 2018.
A changing climate in Mesa County will likely induce longer
summertime warm periods, earlier onset of spring snowmelt, more precipitation
arriving as rain rather than snow, and longer dry periods with heavier
precipitation events in between. These types of changes could exacerbate
already risky wildfire conditions, place extra pressure on already
stretched water providers and users, provide additional challenges
to winter and summer recreation providers, as well as a decline in
snowpack depth and duration which is closely linked to water availability,
watershed functions and winter ecology impacting every sector important
to the community.
(Res. 61-20, 10-7-20; Res. 32-15, 7-1-15; Res. 05-10, 1-6-10)
Avalanche hazards occur mostly in mountainous regions of Colorado
above 8,000 feet. The vast majority of avalanches occur during and
shortly after winter storms. Avalanches occur when loading of new
snow increases stress at a rate faster than strength develops, and
the slope fails. While most avalanches are caused by the weight of
accumulated snow, other triggers can be caused by human activities
(e.g., skier, snowshoer, and snowmobiler).
(a) Geographic Location.
The geographic extent of this hazard
in Mesa County is isolated – less than 10 percent of the
County is affected.
The avalanches in Mesa County have primarily occurred on the
Grand Mesa which is primarily federally owned land.
(b) Previous Occurrences.
According to the National Climatic
Data Center Storm Events Database and the CAIC information, Mesa County
has had five recorded avalanches from 1959 to 2019.
(1) January 30, 1999 – Nine snowmobilers were traversing the
north side of the Grand Mesa at the 10,600-foot level. The snowmobiler
who was third in line triggered a small hard-slab avalanche which
buried him under five feet of snow ending with unsuccessful resuscitation
efforts.
(2) February 24, 2002 – A snowmobiler triggered a soft-slab
avalanche near Flat Top Mountain in extreme northeast Mesa County,
about eight miles south southwest of Sunlight Ski Area. This avalanche
was about 300 feet across and two feet deep, beginning at an elevation
of just below the 10,200-foot level. The avalanche ran approximately
400 vertical feet. The victim was found after having been buried for
approximately 30 minutes. Resuscitation efforts were unsuccessful.
(3) February 4, 2004 – Avalanche swept across Highway 65 at
mile marker 36 on the Grand Mesa. One vehicle was buried and the road
was closed in both directions until the next day. No injuries or fatalities
reported; however, $5,000 in property damage was reported.
(4) April 1, 2005 – A backcountry skier was killed when he
triggered an avalanche at about 10,560 feet above sea level on the
Grand Mesa while ascending a slope. The skier was swept over some
rocks and down into some trees. His companion notified 911 dispatch
of the incident. CDOT employees and Mesa County Search and Rescue
responded and found the victim approximately two hours after he was
buried.
(5) March 17, 2010 – Two cross country skiers attempted to
ski the Thunderbird area on the west side of the Grand Mesa. The skiers
were passing through a clearing when a wall of snow above them collapsed.
They were both carried an estimated 300 to 800 feet down slope. One
of the skiers was dragged into several trees and seriously injured.
Mesa County Search and Rescue responded and the injured skier was
airlifted to the regional trauma center.
(c) Probability of Future Occurrence.
The probability of
future occurrence for avalanches in Mesa County is considered occasional
or a one to 10 percent chance of happening in the next year.
(d) Magnitude/Severity.
Three out of the four avalanche
events recorded resulted in a death, categorizing the magnitude/severity
of this hazard as critical.
(Res. 61-20, 10-7-20; Res. 32-15, 7-1-15; Res. 05-10, 1-6-10)
(a) Hazard Description.
Dams are manmade structures built
for a variety of uses, including flood protection, power, agriculture,
water supply, and recreation. Dams typically are constructed of earth,
rock, concrete, or mine tailings. Two factors that influence the potential
severity of a full or partial dam failure are the amount of water
impounded and the density, type, and value of development and infrastructure
located downstream.
Dam failures can result from any one or a combination of the
following causes:
(1) Prolonged periods of rainfall and flooding, which result in overtopping
(overtopping is the primary cause of earthen dam failure);
(3) Inadequate spillway capacity resulting in excess overtopping flows;
(4) Internal erosion caused by embankment or foundation leakage or piping
or rodent activity;
(8) Failure of upstream dams on the same waterway.
(b) Geographic Location.
The geographic extent of this hazard
in Mesa County is small – 10 to 25 percent of the County
is affected.
The Colorado Division of Water Resources provided a list of
dams in Mesa County as shown in Table 6 and their classification based
on the potential hazard to the downstream area resulting from failure
of the dam:
(1) Class I (High Hazard): Failure of dam would likely result in loss
of life.
(2) Class II (Significant Hazard): Failure of dam would not cause loss
of life, but would cause extensive and/or severe property damage.
Based on these classifications, there are 23 high hazard dams
and 28 significant hazard dams in Mesa County. High and significant
hazard dams all have emergency action plans in place.
|
Table 6: Class I – Class II Hazard Dams
|
---|
Dam Name
|
Hazard Class
|
Year Completed
|
---|
ALSBURY
|
1
|
1996
|
BIG CREEK #1
|
1
|
1893
|
BIG CREEK #3
|
1
|
1893
|
BONHAM-WELLS
|
1
|
1900
|
BULL CREEK #4
|
1
|
1901
|
COON CREEK #1
|
1
|
1900
|
COTTONWOOD #1
|
1
|
1894
|
COTTONWOOD #2
|
1
|
1895
|
COTTONWOOD #5
|
1
|
1909
|
HALLENBECK #1
|
1
|
1970
|
INDIAN WASH DET.
|
1
|
1965
|
JERRY CREEK #1
|
1
|
1964
|
JERRY CREEK #2
|
1
|
1978
|
JERRY CREEK DIKE 1
|
1
|
1978
|
JUNIATA
|
1
|
1979
|
KITSON
|
1
|
1911
|
LEON LAKE
|
1
|
1898
|
PARKER BASIN #1
|
1
|
1899
|
PARKER BASIN #3
|
1
|
1899
|
SOMERVILLE-McCULLAH
|
1
|
1972
|
UPPER HIGHLINE
|
1
|
1967
|
VEGA
|
1
|
1959
|
Y T RANCH
|
1
|
1911
|
ANDERSON #1
|
2
|
1963
|
ANDERSON #2
|
2
|
1974
|
BIG BEAVER
|
2
|
1947
|
BOLEN
|
2
|
1973
|
BULL BASIN #2
|
2
|
1953
|
BULL CREEK #5
|
2
|
1901
|
CASTO
|
2
|
1940
|
COLBY HORSE PARK
|
2
|
1956
|
COTTONWOOD #4
|
2
|
1896
|
CRAIG #1
|
2
|
1951
|
CRAIG #2
|
2
|
1960
|
DEEP CREEK #2
|
2
|
1906
|
FLOWING PARK
|
2
|
1973
|
FRUITA #1
|
2
|
1949
|
FRUITA #2
|
2
|
1959
|
GARDNER LAKE
|
2
|
1980
|
GOBBO #1
|
2
|
1973
|
GOBBO #3
|
2
|
1973
|
GRAND MESA #1
|
2
|
1887
|
GRAND MESA #8
|
2
|
1901
|
HALLENBECK #2
|
2
|
1943
|
HOGCHUTE
|
2
|
1947
|
MESA CREEK #1
|
2
|
1893
|
MESA CREEK #3
|
2
|
1890
|
MESA CREEK #4
|
2
|
1892
|
MONUMENT #1
|
2
|
1960
|
PALISADE CABIN
|
2
|
1956
|
RAPID CREEK #1
|
2
|
1934
|
Figure 6 is a map showing locations of the Class I and II Dams
in Mesa County.
|
Figure 6: Map of Dams in Mesa County
|
(Mesa County GIS)
|
(c) Previous Occurrences.
(1) June 1983 – Grand Mesa Dam No. 8 overtopped and failed
during spring runoff due to emergency spillway being blocked by snow
and ice. Snowmelt produced high inflow to the reservoir which overtopped
dam. Minor flooding downstream with damage to Highway 65 and Lands
End Road. Significant damage was reported to the dam. Dam was repaired
and spillway enlarged.
(2) Spring 1998 – Fruita No. 1 dam located at the head of
North East Creek south of Glade Park failed as a result of failing
downstream slope. This slope failed on two separate occasions; reservoir
level was restricted until dam was rehabilitated in 2009. Because
this failure happened during normal operations, actual flooding was
prevented.
(3) 1996 – Upper Highline Dam in unincorporated Mesa County
(Mack) suffered settling and deformation of the dam. The dam crest
settled several feet at the west end and reservoir was drained so
dam could be rehabilitated. This intervention prevented failure and
flooding. Significant damage reported to State-owned dam.
(4) 1983 – Vincient No. 2 dam (above the Town of Palisade)
overtopped during spring runoff and failed. When a hazard classification
is given to a dam, it is done so based on the consequences of the
dam’s failure absent flooding conditions, i.e., on a clear day
in summer with the stream at a “normal” level. When Vincient
No. 2 failed, the stream below was running bank-full from snowmelt
and the resulting failure discharge jumped out of the channel and
did more damage downstream than would have normally occurred. It is
important to remember that a low hazard dam can still cause a significant
amount of damage and possibly result in loss of life, depending on
the timing of the failure. (Jackson, 2009)
(d) Probability of Future Occurrence.
The probability of
future occurrence is occasional, meaning there is a one to 10 percent
chance of occurrence in the next year or has a recurrence interval
of 11 to 100 years. Due to the documented cases above, there is a
possibility of future dam failures.
(e) Magnitude/Severity.
Depending on the hazard class of
the dam, the magnitude/severity of a dam failure is listed as catastrophic.
Multiple deaths, destroyed or severely damaged property, and/or interruption
of essential facilities and services is possible. As indicated above,
Mesa County has several Class I (High Hazard) dams which would cause
loss of life upon failure of the dam.
(Res. 61-20, 10-7-20; Res. 32-15, 7-1-15; Res. 05-10, 1-6-10)
(a) Hazard Description.
Drought is a normal, recurrent feature
of climate, although some consider it a rare and random event. It
occurs in virtually all climatic zones, but characteristics vary significantly
from one region to another. It originates from a deficiency of precipitation
over an extended period of time, usually a season or more. (University
of Nebraska Lincoln, 2009)
Due to Colorado’s semiarid conditions, drought is a natural
but unpredictable occurrence in the State. The onset of drought in
western Colorado counties is usually signaled by a lack of significant
winter snowfall.
(b) Geographic Location.
The geographic location of this
hazard is considered large in Mesa County, with more than 50 percent
of the County affected.
(c) Previous Occurrence.
According to the National Climatic
Data Center, Mesa County and respective towns and municipalities have
experienced several drought periods over time. Since 1999 Mesa County
was experiencing multi-year drought conditions and beginning in May
of 2002, western Colorado was experiencing its first full month of
severe to extreme drought conditions. The most intense drought classification,
exceptional drought conditions, had developed. Low elevation snowpack
had already melted throughout the area and many seasonal streams dried
up by the end of May.
The drought began to have a major impact on agricultural interest
and to a lesser degree on the outdoor recreational industry. Perhaps
of most importance, the drought created a large potential for major
wildfires. Below is a list of drought occurrences as recorded by the
National Climatic Data Center.
(1) May 2002 – May was the first full month of severe to extreme
drought conditions in western Colorado. The most intense drought classification,
exceptional drought conditions, had developed in the southwest corner
of the State by the end of the month. Low elevation snowpack had already
melted throughout the area before May, with many seasonal streams
dried up by the end of May. In May, the drought began to have a major
impact on agricultural interests, and to a lesser degree on the outdoor
recreation industry. Perhaps of most importance, the drought created
a large potential for major wildfires.
(2) July 2003 – Severe to extreme drought conditions continued
across western Colorado during the month. Although monsoon moisture
did bring thunderstorms to the area, significant rainfall amounts
were not widespread in coverage. Additionally, record high temperatures
occurred through much of the month.
(3) July 2004 – Surges of subtropical moisture in monsoonal
flow resulted in a few bouts of widespread precipitation across western
Colorado during the month, with locally heavy rains occurring in some
areas. However, this had little impact on the long-term drought situation
across the area, and moderate to severe drought continued across most
of western Colorado.
(4) July 2005 – Occasional surges of monsoonal moisture resulted
in periods of thunderstorms across western Colorado during the month
of July, mainly during the second half of the month. However, typical
hot conditions persisted for much of the month and the rainfall that
did occur had little impact on the drought conditions across the area.
Northwest Colorado remained in moderate to severe drought conditions.
Although the remainder of western Colorado was no longer categorized
as being in a drought, multiple years of below normal precipitation
continued to cause water supply concerns.
(5) March 2007 – Below normal precipitation through the month
caused an increase in the dryness and drought conditions across western
Colorado.
(6) March 2012 – Moderate drought conditions expanded westward
into the upper reaches of the Grand Valley by the end of March while
abnormally dry conditions remained in place across the western portion
of the valley through March as precipitation remained well below normal.
(7) 2018 – Severe (D2) drought conditions began to intrude
over the southern portion of Mesa County by late December 2017. Early
to mid January saw the severe drought encompass the entirety of Mesa
County. This persisted until the end of February when the Extreme
(D3) drought conditions moved into the southern portion of Mesa County.
A few storms moving through the region saw this area of extreme drought
be trimmed back until it rebuilt back over the entire county by early
July. Throughout the summer, several sites in Mesa County saw their
record warmest temperatures or had temperatures well above normal.
The Grand Junction area recorded 14 days of high temperatures at or
above 100 degrees in 2018 and had 90 degrees or more 90 times throughout
the year. Early September saw the Exceptional (D4) drought creep into
the southeast portion of Mesa County and eventually expand over the
eastern portion of the County by early October. This was a result
of a dismal monsoon season with prolonged hot and dry conditions over
the region. However, the drought finally improved after a few wet
weeks in October which eradicated the exceptional and extreme drought
conditions over Mesa County. Grand Junction had 11 consecutive days
of precipitation from October 1-11, 2018 with 2.53 inches total. Additionally,
Grand Junction finished as the fourth wettest October on record with
2.76 inches (1.70 inches above normal for the month). By the end of
2018, most of Mesa County was in the severe drought category. Continual
gradual improvement occurred during the first few months of 2019 with
all traces of the drought gone in Mesa County by mid May 2019.
(d) Probability of Future Occurrence.
The probability of
future occurrence is occasional, meaning there is a one to 10 percent
chance of occurrence in next year or has a recurrence interval of
11 to 100 years. According to the Colorado Drought Mitigation and
Response Plan, Colorado was in a drought for 48 of the past 115 years
(1893 – 2007). Therefore a 42 percent chance exists that
a drought will happen in Colorado in any given year. (J. Truby, January
2001)
(e) Magnitude/Severity.
The magnitude/severity of drought
conditions is limited. Drought impacts in Mesa County can be wide
reaching: economic, environmental, and societal. The most significant
impacts in Mesa County and respective jurisdictions are related to
wildfire protection and agriculture. Mesa County economy consists
of a number of fruit and vegetable growers who are heavily impacted
by drought conditions.
(Res. 61-20, 10-7-20; Res. 32-15, 7-1-15; Res. 05-10, 1-6-10)
(a) Hazard Description.
Earthquakes are defined as the sudden
release of energy occurring from the collision or shifting of crustal
plates on the earth’s surface or from the fracture of stressed
rock formations in that crust. The release of energy results in the
earth shaking, rocking, rolling, jarring and jolting; having the potential
to cause minimal to great damage. Earthquakes are measured by units
of magnitude, which is a logarithmic measure of earthquake size. This
means that at the same distance from the earthquake, the shaking will
be 10 times as large during a magnitude 5 earthquake as it would during
a magnitude 4 earthquake. (EHP Web Team, 2009)
Earthquakes can cause structural damage, injury, and loss of
life, as well as damage to infrastructure networks, such as water,
power, communication and transportation systems. Secondary impacts
can include landslides, liquefaction, fires, and dam failure.
(b) Geographic Location.
Colorado is comprised of areas
with low to moderate potential for damaging earthquakes, based on
research by geologists and geophysicists who specialize in seismology.
There are about 90 potentially active faults that have been identified
in Colorado, with documented movement within the last 1.6 million
years. However, there are several thousand other faults that have
been mapped in Colorado that have not been sufficiently studied to
know whether they are capable of generating earthquakes or not.
It is not possible to accurately estimate the timing or location
of future dangerous earthquakes in Colorado. The lack of an adequate
network of seismometers in Colorado makes it difficult to detect and
locate earthquakes. Moreover, the historical record is quite short
(~150 years). Nevertheless, the available seismic hazard information
can provide a basis for a reasoned and prudent approach to seismic
safety. (Subcommittee, 1999)
Mesa County has a considerable amount of fault lines as shown
in Figure 7 that are located within the County but has not recently
experienced a significant earthquake event.
(c) Previous Occurrences.
Many of Colorado’s earthquakes
occur in mountainous regions of the State with some having been located
in the western valley and plateau region. The Colorado Geological
Survey has estimated that the largest earthquake possible on the Western
Slope of Colorado is magnitude 6.5. This estimate is based on studies
of the fault systems in western Colorado. The two largest fault systems
in western Colorado are associated with the Uncompahgre Uplift and
the White River Uplift.
The areas of most concern are the Uncompahgre Plateau and Paradox
Valley. The Uncompahgre has the greatest potential for producing a
large natural event. The Paradox Valley has the greatest potential
for creating a large manmade seismic event. Below are the two significant
events that have occurred in Mesa County.
(1) 1971 – 4.5 magnitude earthquake, Glade Park Fault (unincorporated
Mesa County).
(2) 1975 – 4.4 magnitude earthquake northeast of Fruita, Colorado
(Mesa County).
(d) Probability of Future Occurrence.
The probability of
future occurrence for an earthquake in Mesa County or neighboring
jurisdictions is occasional resulting in a one to 10 percent chance
of occurrence in the next year or has a recurrence interval of 11
to 100 years.
(e) Magnitude/Severity.
The magnitude/severity of an earthquake
is limited resulting in minor injuries and illnesses, minimal property
damage that does not threaten structural stability and/or interruption
of essential facilities and services for less than 24 hours.
Figure 7: Faults in Mesa County
|
Source: Mesa County GIS
|
(Res. 61-20, 10-7-20; Res. 32-15, 7-1-15; Res. 05-10, 1-6-10)
(a) Hazard Description.
Flooding has occurred repeatedly
throughout Mesa County and will continue to occur. FEMA defines “flooding”
as “a partial or complete inundation of normally dry land areas
from (1) the overland flow of a lake, river, stream, ditch, etc.;
(2) the unusual and rapid accumulation or runoff of surface waters;
and (3) mudflows or the sudden collapse of shoreline land.”
(www.training.fema.gov/EMIWeb/IS/IS394A/glossary-0306.doc)
Snowmelt flooding is characterized by moderate peak flows, large
volume, and long duration, and is marked by a diurnal fluctuation
in flow. Rainfall on melting snow may speed up the melting process
and increase flood flow. General rain floods are caused by prolonged
heavy rainfall over large areas and are characterized by high peak
flows of moderate duration. Cloudburst floods characteristically have
high peak flows, high velocities, short durations, and small volumes
of runoff. (FEMA, Flood Insurance Study, Mesa County Colorado, 2009)
The area adjacent to a river channel is its floodplain. In its common usage, “floodplain” most often refers to that area that is inundated by the 100-year flood, the flood that has a one percent chance in any given year of being equaled or exceeded. Other types of floods include general rain floods, thunderstorm generated flash floods, alluvial fan floods, dam failure floods (see GJMC §
42.08.220, Dam failure), and local drainage floods. The 100-year flood is the national standard to which communities regulate their floodplains through the National Flood Insurance Program.
The potential for flooding can change and increase through various
land use changes. A change in environment can create localized flooding
problems inside and outside of natural floodplains by altering or
confining watersheds or natural drainage channels. These changes are
commonly created by human activities. These changes can also occur
as the result of other events such as wildfires. Wildfires create
hydrophobic soils, in which the soils harden preventing rainfall from
being absorbed into the ground.
FEMA also defines “flash flooding” as “flood
that arises very quickly, occurring suddenly, within a short time
(from minutes to less than six hours), and usually is characterized
by high flow velocities. Flash floods often result from intense rainfall
over a small area, usually in areas of steep terrain.” (www.training.fema.gov/EMIWeb/IS/IS394A/glossary-0306.doc)
Flooding in Mesa County is caused mainly by snowmelt in the
larger drainage basins and by cloudbursts over the smaller drainage
basins. However, general rainstorms constitute the principal flood
hazard on Roan Creek, while general rain on snowpack creates the most
hazardous conditions in the basins of Plateau and Buzzard Creek. Major
floods on the Colorado and Gunnison Rivers result from rapid melting
of the mountain snowpack during May, June, and July and the Dolores
River experiences flooding from both snowmelt and general rainstorms.
Mesa County has received a copy of the 2012 Flood Insurance
Study that covers the Town of Collbran, Town of DeBeque, City of Fruita,
City of Grand Junction, Mesa County unincorporated areas, and Town
of Palisade. This study has developed flood risk data for various
areas of the community that will be used to establish actuarial flood
insurance rates. This information will also be used by Mesa County
to update existing floodplain regulations as part of the Regular Phase
of the National Flood Insurance Program (NFIP), and by local and regional
planners to further promote sound land use and floodplain development.
The following table details information provided by the Colorado
Water Conservation Board regarding the number of active flood insurance
policies in Mesa County communities in 2018. With this plan update,
there remains a single repetitive loss property in Mesa County (unincorporated
area) (parcel no. 2697-273-00-063) with the following claims: claim
no. 1: 6/8/95 in the amount of $750; claim no. 2: 7/1/99 in the amount
of $2,267; and claim no. 3: 7/10/01 in the amount of $1,973. This
property is partially within the FEMA regulatory floodway and partially
within the regulatory special flood hazard area.
Jurisdiction
|
Num. Policies
|
Total Coverage
|
Claims since 1978
|
Total paid since 1978
|
---|
Mesa County
|
156
|
$39,492,000
|
38
|
$262,065
|
Town of Collbran
|
8
|
$2,235,400
|
4
|
$15,827
|
City of Grand Junction
|
120
|
$29,238,600
|
20
|
$228,328
|
City of Fruita
|
10
|
$3,347,100
|
5
|
$5,047
|
Town of Palisade
|
7
|
$1,952,700
|
2
|
$0
|
Town of DeBeque
|
1
|
$105,000
|
0
|
$0
|
(b) Geographic Location.
All streams in Mesa County are
either direct or indirect tributaries of the Colorado River, which
traverses the north-central and northwestern sectors. From the northern
County line, the river flows southwesterly for 41 miles to its confluence
with the Gunnison River, thence northwesterly 27 miles, and again
southwesterly for 15 miles in its remaining course in the County.
In general, the Dolores River, Gunnison River, and West Creek
systems drain the western, southwestern, and south-central portions
of the County. The Plateau Creek system drains the eastern sector,
except for the easternmost portion, which is drained by the Divide
Creek system, which flows northerly to the Colorado River in Garfield
County. A group of minor creeks and washes flowing southerly from
the Roan and Bookcliffs regions drain the northwestern portion of
the County, and a group of similar streamways convey drainage to the
river from the north-central portion.
Plateau Creek has its headwaters in the Grand Mesa National
Forest, approximately 18 miles southeast of the Town of Collbran.
The stream flows northwesterly from its origin near Chalk Mountain
into Vega Reservoir, approximately 11 miles upstream from Collbran.
Plateau Creek then continues westerly from Vega Reservoir through
Collbran to its confluence with the Colorado River.
Mesa County is subject to major stream flooding caused by rapid
snowmelt, usually associated with rising temperatures and flash flooding
caused by rains associated with thunderstorms. Spring runoff usually
reaches its peak in June and recedes to a normal flow by mid-July.
Mesa County typically experiences the monsoonal weather patterns in
late July and August that create the potential for flash flood events
found in the steeper drainage areas of the County. It is these events
that have the greatest potential for causing major flooding in Mesa
County and typically involve localized flooding and debris-flow issues.
(c) Previous Occurrences.
Mesa County has a long history
of flooding from summer cloudburst storms and from snowmelt runoff.
Seven major flood events have occurred on the Colorado River, four
on the Gunnison River, and four on the Dolores River. Floods occurred
in 1884, 1917, 1920, 1921, 1935, 1952, 1957, 1983, and 1984 on the
Colorado River; in 1884, 1920, 1921, and 1957 on the Gunnison River;
and in 1884, 1909, 1911, and 1958 on the Dolores River. Most known
floods in Mesa County resulted from snowmelt, sometimes augmented
by general rain. The largest snowmelt flood runoff of record on the
Colorado River occurred in June 1921. Heavy rain on June 14th and
15th augmented runoff to produce a peak flow of 81,000 cfs near Fruita.
Flooding from general rain occurred on the Dolores River in
September 1909 and October 1911. Snowmelt flooding on the Dolores
River in April 1958 inundated 1,100 acres in the Gateway area and
resulted in damage estimated at $230,000.
Recorded cloudburst floods occurred on Indian Wash (Grand Junction
area) in June 1958 and on West Creek (Gateway area) in July 1940.
The West Creek cloudburst covered approximately 25 square miles of
the drainage area and produced a peak flow estimated at 11,700 cfs.
The most recent serious floods on the Colorado River occurred
in 1983 and 1984. Peak flows on the Colorado River at the State line
were approximately 61,000 and 70,000 cfs in 1983 and 1984 respectively.
Colorado River flood flows in the Grand Junction area inundated streets,
lawns, and gardens; deposited sand, silt, and debris; and flooded
basements and lower floors in residential areas in the Riverside Park,
Rosevale and Connected Lakes area southwest of the City in 1983 and
1984 but have not caused significant damage since these events. The
flooding events in 1984 resulted in loss of life as did the flooding
event that occurred on I-70 when Bosley Wash flooded in 2008 resulting
in a drowning.
The Riverside Park area has experienced repeated flood danger
as the erosion and undermining of protective levees has necessitated
extensive flood fighting and levee repair. These noncertified levee
and storm drain system improvements serve to mitigate potential flooding.
The principal cause of flooding on Plateau Creek and Buzzard
Creek is a rapidly melting heavy snowpack during May, June, and July.
Rainfall on melting snow may hasten the melting process and increase
flood flows. A major flood occurred on Plateau Creek in 1922. Based
on the record from a stream gage on Plateau Creek located approximately
six miles east of Collbran, this flood had an estimated discharge
of 3,080 cfs which corresponds to a frequency in excess of 100 years.
On May 27, 2016, heavy snowmelt on the Grand Mesa during spring
runoff caused an estimated 30,000 cubic meters of dirt and rock to
slide off the head scarp of the West Salt Creek Landslide into the
sag pond formed by the landslide. This caused a large volume of water
in the sag pond to overflow the debris dam and cut a channel up to
100 feet deep and 50 feet wide down the 2.8-mile long landslide deposit.
The flood waters continued down below the landslide along West Salt
Creek at depths over 12 feet and then down to the larger Plateau Creek
where the flood waters came up to within one foot of Rodeo Road in
the Town of Collbran. The flash flood caused damage to some roads,
fences, a barn and horse riding arena.
(d) Probability of Future Occurrence.
The probability of
future occurrence is highly likely with a near 100 percent chance
of occurrence next year or it happens every year. Due to the documented
cases above and the information collected on events that were smaller
in size, Mesa County and the various towns/municipalities will continue
to deal with flood-related activities in the future.
(e) Magnitude/Severity.
The magnitude/severity of a flood
event is limited resulting in minor injuries and illnesses, minimal
property damage that does not threaten structural stability and/or
interruption of essential facilities and services for less than 24
hours. Most of the flood events that have occurred in Mesa County
over the past 10 years have been limited with respect to injuries
and property damage. Figure 8 shows the major rivers and tributaries
within Mesa County.
Figure 8: Rivers and Tributaries
|
(Nelson, 2009)
|
(Res. 61-20, 10-7-20; Res. 32-15, 7-1-15; Res. 05-10, 1-6-10)
(a) Hazard Description.
A hazardous material is any item
or agent (biological, chemical, physical, radiological) that has the
potential to cause harm to humans, animals, or the environment, either
by itself or through interaction with other factors. The release of
hazardous materials can happen either by accident or as a result of
criminal activity and can threaten people and natural resources in
the immediate vicinity of the accident, including residences and businesses
along transportation routes.
(b) Geographic Location.
Mesa County is a center of commerce
in western Colorado and hazardous materials are commonly transported
through the County by truck and rail. Designated truck routes are
State Highways 139, 141, 50 and U.S. Interstate 70. The Union Pacific
Railroad operates two rail lines in Mesa County. Their main line is
located primarily along the Colorado River through the County. The
secondary line (southern leg) branches off the main line near the
confluence of the Gunnison and Colorado Rivers and is located along
the Gunnison River.
It is observed that the majority of the products transported
through Mesa County belong to the hazard classes of 2 (Flammable and
Combustible Gases), 3 (Flammable and Combustible Liquids), 8 (Corrosive
Materials), and 9 (Miscellaneous Hazardous Materials). There are currently
193 Tier II reporting fixed site facilities in Mesa County. These
facilities either produce, store, and/or use hazardous materials and
are required by the Environmental Protection Agency to report these
quantities under Tier II reporting requirements.
(c) Previous Occurrences.
Two significant incidents have
occurred in Mesa County as a result of illegal dumping of hazardous
materials. The first incident involved illegal dumping in the Cactus
Park area of Mesa County of three 150-pound cylinders of liquid chlorine
with safety caps removed. This case resulted in a felony conviction
of a 30-year-old male who received eight years in the Colorado State
Corrections System. This case was the first successful prosecution
of the “Clean Air Act” in the State of Colorado. (Reekie,
2009)
The second case occurred in 2001 and was the result of illegal
discharging of ethylene glycol into the Colorado River. The facility
was discharging through the conveyance of storm water system piping
directly into the Colorado River. The illegal discharges resulted
in a substantial “fish kill” to native aquatic life. This
case resulted in a felony conviction of the corporation and individuals
responsible. The environmental remediation was conducted by the Environmental
Protection Agency. Remediation costs were approximately $1,500,000.
The business was charged with felony charges resulting in significant
fines and imprisonment. This case was the first successful prosecution
of the “Clean Water Act” in the State of Colorado. (Reekie,
2009)
The Grand Junction Fire Department that serves as the Designated
Emergency Response Authority for the entire planning area identified
the following as significant incidents in Mesa County:
(1) 1990 – Motor Carrier 338 carrying 70,000 pounds of liquid
oxygen caused one injury and $70,000 in damage.
(2) 1991 – Motor Carrier 331 carrying propane caused $100,000
in damage due to remediation of highway shoulder from diesel contamination.
(3) 1991 – Illegal dumping of three 150-pound cylinders of
liquid chlorine with safety caps removed in Cactus Park area.
(4) 1992 – Two tractor trailer 40-foot cargo trailers (MC
331 carrying propane) collide causing two injuries and $200,000 in
damage.
(5) 1992 – Motor Carrier 306 with 7,000 gallons of naphtha
crashes into rock wall on Highway 141. Highway closed for 36 hours.
$200,000 in damage.
(6) 1995 – Hazardous materials release at fixed facility.
Nitric acid tank endothermic reaction at fixed facility. Resulted
in $60,000 in damages.
(7) 2001 – Illegal discharge of ethylene glycol into the Colorado
River.
(8) 2002 – Hazardous materials release from Amtrak derailment
in Ruby Canyon with 123 passengers on board; $300,000 in property
damage and $20,000 in environmental remediation.
(9) 2008 – Hazardous materials release with two tractor trailers
with coal and hydrochloric acid with property damage of $250,000 and
$80,000 in environmental remediation.
(10) 2011 – Tanker rolled 30 feet down an embankment on Highway
141 resulting in loss of two-thirds of its 7,000 gallon light crude
oil cargo.
(11) 2013 – Approximately 26 pounds of chlorine leaked at a
water utility as a result of a valve not being shut properly.
(12) 2014 – Approximately 100 pounds of ammonia leaked from
a refrigeration unit at a business.
(d) Probability of Future Occurrence.
Highly likely –
near 100 percent chance of occurrence next year or it happens every
year. Hazardous materials related incidents occur in Mesa County every
year. Most often these incidents involve the transportation sector
and are often fuel spills or cargo that is being transported.
(e) Magnitude/Severity.
The magnitude/severity of a hazardous
materials incident in Mesa County has been limited with impacts to
the environment, property destroyed or severely damaged, and/or interruption
of essential facilities and service for more than 72 hours.
Impacts in the past have been limited, but depending on the
type and quantity of material released, an event could have serious
consequences to the public. Humans and animals are affected through
inhalation, ingestion, or direct contact with the skin. Air releases
can prompt large-scale population evacuations and spills into water
or onto the ground can adversely affect public water and sewer systems.
(Res. 61-20, 10-7-20; Res. 32-15, 7-1-15; Res. 05-10, 1-6-10)
(a) Hazard Description.
The Colorado Geological Survey department
defines landslides as the downward and outward movement of slopes
composed of natural rock, soils, artificial fills, or combination
thereof. Landslides move by falling, sliding, and flowing along surfaces
marked by difference in soil or rock characteristics. A landslide
is the result of a decrease in resisting forces that hold the earth
mass in place and/or an increase in the driving forces that facilitate
its movement.
Landslides as defined above include two major types: (1) rotational
slides which refer to all landslides having a concave upward, curved
failure surface and involving a backward rotation of the original
slide mass; and (2) translational slides in which the surface of rupture
along which displacement occurs is essentially planar. Either type
of landslides can involve various combinations of bedrock, broken
bedrock, and unconsolidated superficial material, and the displaced
material in either type of slide may be either greatly deformed or
nearly intact.
Rate of movement of landslides varies from very slow to very
rapid. They may be extremely small in extent or measurable in miles.
Volumes of material involved may range from a few cubic feet to millions
of cubic yards. Landslides result from some change in the physical
condition of an unstable slope area (see section of guidelines on
potentially unstable slopes). Such changes may be natural or man-induced.
A rockfall is the falling of a detached mass of rock from a
cliff or down a steep slope. Weathering and decomposition of geological
materials produce conditions favorable to rockfalls. Rockfalls occur
most frequently in mountains or other steep areas during the early
spring when there is an abundance of moisture and repeated freezing
and thawing. (Survey, 2004)
(b) Geographic Location.
The geographic location of landslides
and rockfalls throughout Mesa County is isolated – which
is less than 10 percent of the area.
The landslides and rockfalls that have occurred in Mesa County
are most typically associated with canyons. The areas most affected
by landslides-rockfalls include: Interstate 70 in DeBeque Canyon and
along the Bookcliffs, Highway 65 in Plateau Canyon, Highway 141 in
John Brown Canyon near Gateway, Colorado, and the area encompassing
the Colorado National Monument.
The DeBeque Canyon Landslide is a major landslide complex in
western Colorado that has historically impacted the east-west highway
and railway corridor on the Colorado River as shown in Figures 9 and
10.
Figure 9: Mesa County Landslide Map
|
Source: Mesa County GIS
|
Figure 10: DeBeque Canyon Slide Area
|
(Survey, 2004)
|
Figure 11: Photo of DeBeque Canyon Slide Area –
Interstate 70
|
Figure 12: Photo of DeBeque Canyon Slide Area –
Interstate 70
|
(Photos taken by Mesa County Emergency Management –
1998 Slide in DeBeque Canyon)
|
Figure 13: Rockfall West of Palisade Along Interstate
70
|
(Photos taken by Mesa County Emergency Management, July 8, 2009)
|
Figure 14: Rockfall Event in DeBeque Canyon at Beaver
Tail Tunnel on Interstate 70
|
Figure 15: Rockfall Event in DeBeque Canyon at Beaver
Tail Tunnel on Interstate 70
|
(Photos taken by Mesa County Emergency Management 10/26/09)
|
(c) Previous Occurrences.
The DeBeque Canyon Landslide,
which is considered a major landslide complex, has had three significant
reactivations or ground movements during the past century. The precise
date of the first major movement is unknown but occurred in the late
1890s or early 1900s. That slide movement was the largest and reportedly
shifted the river channel and damaged railroad facilities on the north
bank of the Colorado River.
The second noteworthy movement occurred in February 1958 when
the roadway was widened for a modern two-lane highway. The widening
resulted in further cutting and destabilizing of the landslide toe,
with subsequent movements resulting in the heaving of the roadway
23 vertical feet. In April 1998, the third major movement occurred
and caused Interstate 70, constructed in the mid-1980s, to heave 14
vertical feet. This highway also shifted five to six feet laterally
towards the river during this event as shown in Figures 11 and 12.
(Survey, 2004)
In 2004, rain and snow loosened several rocks resulting in several
injuries to motorists traveling on Interstate 70. In 2006 a rockfall
along Interstate 70 just outside of the Town of Palisade resulted
in a 300-pound boulder hitting several cars traveling on Interstate
70, injuring several motorists who required medical treatment. Additional
rockfall activity has occurred in the DeBeque Canyon resulting in
isolated deaths and injuries.
In July of 2009 a significant rockfall occurred on the Bookcliffs
approximately two miles west of the Town of Palisade; see Figure 13.
What was unique about this rockfall was the amount of energy associated
with it. This particular event registered a 2.6 on the Richter scale
and was first thought to have been an earthquake. After hours of analysis
it was determined that the event was actually a rockfall event, possibly
triggered due to the moisture in the soil.
A rockfall event occurred in DeBeque Canyon near the Beaver
Tail tunnel on Interstate 70. A significant amount of large boulders
landed on the interstate closing all lanes of traffic for a period
of time as seen in Figures 14 and 15. No injuries were reported.
The West Salt Creek Landslide occurred on May 25, 2014, near
the town of Collbran in eastern Mesa County. The landslide mobilized
30,000,000 cubic meters of material and took the lives of three men.
The landslide cut off West Salt Creek and the rotated slide block
created a sag pond that detains the flow of West Salt Creek. This
incident resulted in both local and State emergency declarations.
Considerable work has been done to establish monitoring systems and
understand the hazard of the remaining slide block and sag pond. Monitoring
will be ongoing for a number of years. The West Salt Creek Landslide
can be seen in Figures 16 and 17.
Figure 16: West Salt Creek Landslide Viewed from the East
Flank of the Head Escarpment
|
Figure 17: West Salt Creek Landslide Change in Topography
|
In July, 2019, a DeBeque Canyon land owner allowed water
to flow into his dry rock quarry – in violation of his
permit. The water seeped to canyon walls above Interstate 70 loosening
rocks and endangering motorists on I-70. The Colorado Department of
Transportation spent $1,300,000 to mitigate damage to canyon walls
and to install rock fence.
(d) Probability of Future Occurrence.
The probability of
future occurrence is considered highly likely based on past events.
(e) Magnitude/Severity.
The magnitude/severity of a landslide-rockfall
event in Mesa County is critical. Past events have resulted in isolated
deaths and/or multiple injuries as well as major or long-term property
damage that threatens structural stability and/or interruption of
essential facilities for 24 to 72 hours.
(Res. 61-20, 10-7-20; Res. 32-15, 7-1-15; Res. 05-10, 1-6-10)
(a) Hazard Description.
Lightning is defined as “an
abrupt, discontinuous natural electric discharge in the atmosphere.”
The rising air in a thunderstorm cloud causes various types of frozen
precipitation to form within the cloud. Included in these precipitation
types are very small ice crystals and much larger pellets of snow
and ice. The smaller ice crystals are carried upward toward the top
of the clouds by the rising air while the heavier and denser pellets
are either suspended by the rising air or start falling toward the
ground. Collisions occur between the ice crystals and the pellets,
and these collisions serve as the charging mechanism of the thunderstorm.
The small ice crystals become positively charged while the pellets
become negatively charged. As a result, the top of the cloud becomes
positively charged and the middle to lower part of the storm becomes
negatively charged. At the same time, the ground underneath the cloud
becomes charged oppositely of the charges directly overhead.
When the charge difference between the ground and the cloud
becomes too large, a conductive channel of air develops between the
cloud and the ground, and a small amount of charge (step leader) starts
moving toward the ground. When it nears the ground, an upward leader
of opposite charge connects with the step leader. At that instant
this connection is made, a powerful discharge occurs between the cloud
and the ground. We see this discharge as a bright visible flash of
lightning. (NWS, 2008)
Each year in the United States, more than 400 people are struck
by lightning. On average, between 55 and 60 people are killed; hundreds
of others suffer permanent neurological disabilities.
(b) Geographic Location.
The geographic location of this
hazard is considered large as it can happen anywhere in the County.
However, lightning strikes are isolated in that the area that is affected
by a lightning strike is less than 10 percent of the planning area.
(c) Previous Occurrences.
Data from the National Lightning
Network ranks Colorado second in the number of deaths (24) from 2002-2011
for deaths caused by lightning. While lightning is a regular occurrence
in Mesa County, there are few documented cases where lightning has
caused structural damage.
(1) September 13, 1996 – Lightning hit a tree and then traveled
into an adjacent house causing some fire and electrical damage. Estimated
damage was reported at $4,000.
(2) September 6, 1997 – Lightning struck a house on the north
side of the Grand Mesa destroying some electrical items and blackening
a wall on the side of the house.
(3) September 13, 1997 – Lightning struck a tree and power
pole, setting the tree on fire and destroying a power transformer.
Some electrical damage was also incurred at a nearby home.
(4) September 21, 1997 – Lightning strike of a two-story house,
causing the house to catch on fire.
(5) September 9, 1998 – A man was injured when lightning struck
a 12-foot-high pole on a trailer next to the man. The lightning also
struck the man who was jolted off the trailer, landing 20 feet away.
He suffered minor burns.
(6) August 20, 2000 – Lightning struck two horses, killing
one and paralyzing the other. The two horses were found 50 feet apart
from each other.
(7) July 7, 2013 – An intense late night thunderstorm produced
locally heavy rainfall and a lot of lightning in the Grand Valley,
including a lightning bolt that caused significant damage to a childcare
facility.
(8) July 2, 2016 – A thunderstorm produced a lightning bolt
which struck a girl riding an ATV near Glade Park. The girl was injured
but survived.
Many of the lightning strikes that occur in Mesa County are
the cause of wildland fires throughout the County and many strikes
go unreported.
|
(d) Probability of Future Occurrence.
The probability of
lightning strikes in Mesa County is highly likely with a near 100
percent chance of occurrence next year or it happens every year.
(e) Magnitude/Severity.
The magnitude/severity of lightning
throughout Mesa County is limited with minor injuries and illnesses;
minimal property damage that does not threaten structural stability;
and/or interruption of essential facilities and services for less
than 24 hours.
It is recognized that lightning can cause deaths, injuries,
and property damage, including damage to buildings, communications
systems, power lines, and electrical systems.
(Res. 61-20, 10-7-20; Res. 32-15, 7-1-15; Res. 05-10, 1-6-10)
(a) Hazard Description.
Severe winter weather can include
heavy snow, ice, wind chill, blowing snow, freezing rain, sleet, and
extremely cold temperatures. Any of these conditions can immobilize
our community. These conditions can strand commuters, stop supplies
and disrupt power and communication sources. The cost of snow removal,
damage repair, and business losses can have a significant impact on
the community.
Severe winter storms are usually accompanied by high winds,
creating blizzard conditions causing snow to drift, making travel
dangerous. Extreme cold temperatures are often associated with winter
weather and prolonged exposure can be life-threatening. The months
of December, January, and February are the most likely time of the
year for severe winter weather.
Grand Junction receives about two feet of snow per year and
it generally falls a few inches at a time and then melts off. The
ground is usually not covered in snow and there is generally no need
to shovel snow constantly. The winter months dip down into the teens
and occasionally lower. Most years will see a maximum low temperature
for the year of about zero to five degrees Fahrenheit. The average
December-January high is 39 with an average low of 16 degrees Fahrenheit.
The coldest months on average in Mesa County are January and February
and Mesa County’s record minimum temperature was recorded as
-23 degrees Fahrenheit in 1963. (NWS, 2008)
(b) Geographic Location.
The geographic location of severe
winter weather in Mesa County is small with approximately 25 to 50
percent of the County affected. Primarily severe winter weather is
found in the higher elevations of the County and include: Grand Mesa,
Colorado National Monument, and the Uncompahgre areas. The valley
area of the County can see severe winter weather in snowfall, icy
conditions, cold temperatures and wind.
(c) Previous Occurrences.
The National Climatic Data Center
Storm Events Database was used to determine the 287 recorded winter
weather events that included some portion of Mesa County. These events
ranged from heavy snowfall to blowing and drifting snow from significant
wind gusts. (Hinson, National Climatic Data Center, 2009). There have
been 54 events between 2010 to 2013.
On January 9, 2017, an abnormally mild Pacific storm system
produced rainfall which fell into some western Colorado valleys where
trapped air with temperatures below freezing resulted in the formation
of freezing rain. Ice up to half of an inch thick quickly accumulated
on roads and other surfaces at the beginning to the morning commute.
There were hundreds of vehicle accidents and many roads were closed
due to crashed vehicles blocking those roads. There were numerous
injuries to those who slipped and fell. Emergency rooms in the Grand
Valley exceeded their daily admittance records with over 200 people
treated for broken bones and other blunt force injuries. Schools were
closed throughout the Grand Valley and many businesses were negatively
impacted by either not opening, opening late, or the lack of customers.
(d) Probability of Future Occurrence.
The probability of
future occurrence is likely with a 10 to 100 percent chance of occurrence
in next year or has a recurrence interval of 10 years or less. However,
it should be noted that Mesa County on average has much milder winter
seasons than other parts of the State.
(e) Magnitude/Severity.
The magnitude and severity of severe
winter weather in Mesa County is limited – resulting in
minor injuries and illnesses; minimal property damage that does not
threaten structural stability; and/or interruption of essential facilities
and services for less than 24 hours.
Severe winter weather in Mesa County can result in property
damage, localized power outages and force the closure of streets,
highways, schools and businesses. Severe winter weather can escalate,
creating life-threatening situations when emergency response is limited
due to the conditions or when individuals are caught in the backcountry
unprepared. Snow removal costs can also greatly impact local budgets.
(Res. 61-20, 10-7-20; Res. 32-15, 7-1-15; Res. 05-10, 1-6-10)
(a) Hazard Description.
“Wildfire” is the term
applied to any unwanted, unplanned, damaging fire burning in forest,
shrub or grass and is one of the most powerful natural forces known
to humans. While sometimes caused by lightning, nine out of 10 wildfires
are human-caused from smoking, campfires, equipment use, and arson.
On public lands in Mesa County, 74 percent of the wildfires
started are from lightning and 26 percent are human-caused. However,
many of the more destructive and costly fires have been human-caused.
Most of these human-caused fires are started near areas where people
congregate. This can include towns, subdivisions, or campgrounds.
Undoubtedly, human-caused fires on public lands have the potential
to threaten human life as well as property. (Paul, 2009)
Due to fuel accumulation in the form of fallen leaves, branches,
and excessive plant overgrowth in forest and wildland areas, increasing
hot weather, changing weather patterns, and increased residential
development in the wildland-urban interface areas, the potential for
wildfires to occur has increased. The potential for major loss of
property and structures has also significantly increased with the
wildland-urban interface. The risk to firefighters can be high. Similar
fuels/fire/terrain was responsible for 17 firefighter deaths in neighboring
Garfield County. (Paul, 2009)
Based on information contained in the State of Colorado Natural
Hazards Mitigation Plan, a century of aggressive fire suppression
combined with cycles of drought and changing land management practices
has left many of Colorado’s forests unnaturally dense and ready
to burn. Furthermore, the threat of wildfire and potential losses
is constantly increasing as human development and population increases
and the wildland-urban interface expands.
Many other areas of Mesa County now have an increased wildfire
threat in areas where fire was not a problem in the past. This is
due to a combination of irrigation and the introduction of nonnative
plants. Nonnative tamarisk and Russian olive have invaded drainage
areas. Excess, undrained irrigation water has created thick, unbroken
stands of vegetation throughout the Grand Valley. The stands of tamarisk
and Russian olive burn readily and pose a threat to homes and other
structures. The spring 2009 Preserve Fire on the Redlands is a good
example of this kind of fire. (Paul, 2009)
(b) Geographic Location.
The geographic extent of this hazard
in Mesa County is medium – 25 to 50 percent of the planning
area affected.
(c) Previous Occurrences.
According to data collected from
the various Fire Protection Districts, the Mesa County Wildland Fire
Team, the Bureau of Land Management, and the Colorado State Forest
Service, Mesa County has had several significant wildfire events that
have either burned a large amount of acres, structures, or involved
a multi-agency response. These significant fires include the following:
(1) April 3, 1956 – Human caused wildfire at the intersection
of Mesa Street and U.S. Hwy 65 with three structures destroyed.
(2) April, 1978 – Human caused wildfire known as Mesa Creek
Fire (Easter Fire) burned one home with several others damaged.
(3) July 1, 1989 – Lightning caused wildfire burned 1,233
acres with approximately 100 homes evacuated.
(4) July 31, 1995 – Lightning caused wildfire known as Triangle
Fire burned 5,343 acres and forced evacuation of 50 people.
(5) July 4, 2000 – Lightning caused wildfire known as Cone
Mountain Fire burned 4,960 acres. No homes were threatened but forced
road closure of John Brown Canyon.
(6) June 9, 2002 – Lightning strike resulting in wildfire
known as the Miracle Complex Fire that burned 3,951 acres.
(7) June 10, 2002 – Human caused fire known as the Dierich
Creek Fire burned 3,951 acres and forced the evacuation of 57 homes.
(8) July 4, 2004 – Human caused fire known as the 22 1/2 Road
Fire burned 110 acres and threatened 20 homes.
(9) July 29, 2005 – Human caused fire known as the Turkey
Track Fire burned 348 acres, a camp trailer, and the fire protection
district’s water tender. This fire also forced the evacuation
of approximately 20 people.
(10) June 21, 2007 – Human caused wildfire with three homes
destroyed.
(11) July 21, 2008 – Lightning caused fire known as the Housetop
Fire burned 143 acres and threatened multiple gas wells in the area.
(12) August 2, 2008 – Human caused wildfire known as the 48
1/4 Road Fire with one injury and one residence partially burned.
(13) May 11, 2012 – Lightning caused fire known as the Brushy
Mountain Fire burned approximately 170 acres. The fire started on
private land and burned onto National Forest lands on the Uncompahgre
Plateau.
(14) June 26, 2012 – Lightning caused fire known as the Pine
Ridge Fire burned 13,920 acres on private and federal lands. Parts
of the town of DeBeque were evacuated and the fire caused closure
of I-70 and the rail line through DeBeque canyon.
(15) July 10, 2012 – Lightning caused fire known as the Bull
Basin Fire grew rapidly being fueled by extremely dry vegetation,
low relative humidity, high temperatures, and windy conditions. The
fire was quickly contained to approximately 20 acres due to the availability
of severity resources that were prepositioned in Mesa County.
(16) April 2, 2018 – Human caused urban interface fire known
as the Rosevale Fire burned one home, 10 acres and forced 363 homes
to be evacuated. This early season fire occurred prior to spring green-up.
(17) April 19, 2018 – Human caused urban interface fire known
as the Skipper Island fire burned 220 acres, closed I-70 for several
hours, damaged power lines impacting 2,100 power customers. A man
who admitted accidentally starting the fire was sentenced to 80 hours
of community service. This early season fire occurred prior to spring
green-up.
(18) May 25, 2018 – Human caused fire in DeBeque Canyon started
as a result of a vehicle fire on I-70 known as the MM46 fire burned
120 acres, closed I-70 for hours, required evacuation of Island Acres
State Park.
(19) July 29, 2018 – Lightning caused fire, known as Bull Draw
Fire, started in Montrose County and burned into Mesa County on federal
and private land burned 36,549 acres. Fire was not contained until
mid-October, 2018.
(20) July 4, 2019 – Human caused urban interface fire known
as the Riverview Fire burned 10 acres dangerously close to homes under
Red Flag conditions. The fire was started by a juvenile discharging
illegal fireworks. The juvenile plead guilty to fourth-degree arson
and sentenced to 50 hours of public service and restitution in the
amount of $10,000.
(21) August 17, 2019 – Human caused urban interface fire known
as the Peach Festival fire burned five acres adjacent to the Colorado
River near orchards and vineyards. The fire was caused by the Peach
Festival fireworks display. One firefighter was transported to the
hospital due to heat related injuries.
(d) Probability of Future Occurrence.
Highly likely –
Near 100 percent chance of occurrence next year or it happens every
year.
(e) Magnitude/Severity.
Critical – Isolated deaths
and/or multiple injuries and illnesses; major or long-term property
damage that threatens structural stability; and/or interruption of
essential facilities and services for 24 to 72 hours.
Based on data received from the Bureau of Land Management and
Mesa County GIS Department, the following risk assessment has been
mapped out for the planning area. Figure 18 illustrates the areas
where risk is significant if a wildfire were to occur.
Figure 18: Mesa County Wildfire Risk Assessment
|
(Source: Bureau of Land Management)
|
(Res. 61-20, 10-7-20; Res. 32-15, 7-1-15; Res. 05-10, 1-6-10)
(a) Hazard Description.
High winds occur year round in Mesa
County. In the spring and summer, high winds often accompany severe
thunderstorms. These winds are typically straight-line winds, which
are generally any thunderstorm wind that is not associated with rotation.
It is these winds, which can exceed 80 miles per hour (mph), that
represent the most common type of severe weather and are responsible
for most wind damage related to thunderstorms.
(b) Geographic Location.
The geographic extent of this hazard
in Mesa County is large – more than 50 percent of the planning
area affected.
(c) Previous Occurrences.
Historical data from SHELDUS,
NCDC Storm Data, and the National Weather Service, Grand Junction
Office, reported 48 recorded wind events in Mesa County between 1974
and 2008. These wind events also include tornado events that have
occurred in Mesa County. Between 2009 and 2013 there were nine recorded
wind events. Nineteen events were recorded between 2015 and 2019,
including a tornado on the Grand Mesa.
On July 9, 2015, a thunderstorm with rotation produced a tornado
which tracked across a forest of mature aspen trees on the Grand Mesa.
Many aspen trees up to a foot and a half in diameter were either uprooted
or snapped off as high as 15 feet above the ground. The tornado initially
produced damage to trees at the 8,400-foot level and traveled uphill
to about the 8,500-foot level.
(d) Probability of Future Occurrence.
Likely –
10 to 100 percent chance of occurrence in the next year or has a recurrence
interval of 10 years or less.
There were 48 recorded wind events in the past 34 years in Mesa
County which equals 1.4 wind events every year on average, or a 100
percent chance of occurrence in any given year.
(e) Magnitude/Severity.
Limited – Minor injuries
and illnesses; minimal property damage that does not threaten structural
stability; interruption of essential facilities and services for less
than 24 hours.
Windstorms in Mesa County are rarely life-threatening, but do
threaten public safety, disrupt daily activities, cause damage to
buildings and structures, increase the potential for other hazards
(e.g., wildfire), and have adverse economic impacts from business
closures and power loss. Although windstorms are likely to occur in
the future, data indicates the past losses have not been significant,
and the overall magnitude of this hazard is limited.
(Res. 61-20, 10-7-20; Res. 32-15, 7-1-15; Res. 05-10, 1-6-10)
This section summarizes the results of the hazard profiles and
assigns a level of overall planning significance to each hazard of
low, moderate, or high as indicated in Table 7. Significance was determined
based on the hazard profile, focusing on key criteria such as geographic
location, occurrences, magnitude and severity. This assessment was
used by the HMPC to prioritize the hazards that present the greatest
risk to the planning area. The hazards that occur infrequently or
have little or no impact to the planning area were determined to be
of low significance. Those determined to be of high significance were
identified as priority hazards that require additional evaluation
in the vulnerability assessment.
The priorities for this 2020 plan revision have not changed
from the previous plan. The hazards that have been determined to be
of high significance remain wildfire, flood, and landslide/rockfall.
These hazards continue to be the focus in the vulnerability assessment
and the focus of mitigation project proposals.
Table 7: Hazards Profile
|
---|
Hazard Type
|
Geographic Location
|
Occurrences
|
Magnitude/ Severity
|
Total Score
|
Hazard Level
|
---|
Avalanche
|
2
|
4
|
6
|
32
|
M
|
Drought
|
8
|
4
|
4
|
48
|
M
|
Earthquake
|
6
|
4
|
4
|
40
|
M
|
Expansive Soils
|
2
|
4
|
2
|
16
|
L
|
Extreme Heat
|
8
|
4
|
2
|
40
|
M
|
Wildfire
|
6
|
8
|
4
|
80
|
H
|
Flood
|
6
|
8
|
6
|
96
|
H
|
Hailstorm
|
4
|
4
|
2
|
24
|
L
|
Land Subsidence
|
2
|
4
|
4
|
24
|
L
|
Landslide/Rockfall
|
4
|
8
|
6
|
80
|
H
|
Lightning
|
2
|
8
|
4
|
48
|
M
|
Tornado
|
2
|
4
|
2
|
16
|
L
|
Windstorm
|
4
|
6
|
4
|
48
|
M
|
Winter Storm
|
6
|
6
|
2
|
48
|
M
|
Dam Failure
|
4
|
4
|
6
|
40
|
M
|
Hazardous Materials
|
2
|
8
|
4
|
48
|
M
|
(Res. 61-20, 10-7-20; Res. 32-15, 7-1-15; Res. 05-10, 1-6-10)
Requirement Section 201.6(c)(2)(ii)(A): 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 area.
Requirement Section 201.6(c)(2)(ii)(B): [The plan should
describe vulnerability in terms of an] estimate of the potential dollar
losses to vulnerable structures identified in paragraph (c)(2)(i)(A)
of this section and a description of the methodology used to prepare
the estimate.
Requirement Section 201.6(c)(2)(ii)(C): [The plan should
describe vulnerability in terms of] 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.
The vulnerability assessment further defines and quantifies
populations, buildings, critical facilities and infrastructure, and
other community assets at risk to natural hazards. The vulnerability
assessment for this plan followed the methodology described in the
FEMA publication Understanding Your Risks – Identifying
Hazards and Estimating Losses (2002).
The vulnerability assessment is based on the best available
data and the overall planning significance of the hazard. Data to
support the vulnerability assessment was collected from the same sources
identified for the hazard identification and hazard profile sections.
The vulnerability assessment includes three sections:
(a) Community Asset Inventory.
This section is an inventory
of assets exposed to hazards in Mesa County, including the total exposure
of people and property; critical facilities and infrastructure; natural,
cultural, and historic resources; and economic assets.
(b) Vulnerability by Hazard.
This section describes the
County’s overall vulnerability to each hazard; identifies existing
and future structures, critical facilities, and infrastructure in
identified hazard areas; and estimates potential losses to vulnerable
structures, where data is available. Only hazards of moderate or high
significance, or that have identified hazard areas, are addressed
in the vulnerability assessment.
(c) Development and Land Use Trends.
The final section analyzes
trends in population growth, housing demand, and land use pattern.
In addition, a capability assessment was conducted for each
jurisdiction as part of the risk assessment process. A capability
assessment identifies the existing programs, policies, and plans that
mitigate or could be used to mitigate risk to disasters. From a Countywide
perspective the following capabilities are identified in Table 8.
Jurisdiction specific information regarding capabilities is found
in the Jurisdictional Annex of this plan (Article VII of this chapter).
Table 8: Capabilities Matrix
|
---|
Local Mitigation Capabilities Tracker for Local and State
Plan Updates
|
---|
Planning and Regulatory
|
Yes/No
|
---|
Building Codes
|
Yes
|
Building Codes Year
|
Yes
|
BCEGS Rating
|
Yes
|
Capital Improvements Program (CIP) or Plan
|
Yes
|
Community Rating System (CRS)
|
Yes
|
Community Wildfire Protection Plan (CWPP)
|
Yes
|
Comprehensive, Master, or General Plan
|
Yes
|
Economic Development Plan
|
Yes
|
Elevation Certificates
|
Yes
|
Erosion/Sediment Control Program
|
Yes
|
Floodplain Management Plan or Ordinance
|
Yes
|
Flood Insurance Study
|
Yes
|
Growth Management Ordinance
|
Yes
|
Non-Flood Hazard-Specific Ordinance or Plan (e.g., Steep Slope,
Wildfire, Snow Load)
|
No
|
NFIP
|
Yes
|
Site Plan Review Requirements
|
Yes
|
Stormwater Program, Plan, or Ordinance
|
Yes
|
Zoning Ordinance
|
Yes
|
Financial
|
Yes/No
|
---|
Has community used any of the following to fund mitigation activities:
|
|
– Levy for Specific Purposes with Voter Approval
|
No
|
– Utilities Fees
|
No
|
– System Development/Impact Development Fee
|
No
|
– General Obligation Bonds to Incur Debt
|
No
|
– Special Tax Bonds to Incur Debt
|
No
|
– Withheld Spending in Hazard-Prone Areas
|
No
|
– Stormwater Service Fees
|
No
|
– Capital Improvement Project Funding
|
Yes
|
– Community Development Block Grants
|
No
|
– Other (BLM Community Assistance Grant)
|
Yes
|
Administrative and Technical
|
Yes/No
|
---|
Emergency Manager
|
Yes
|
Floodplain Administrator
|
Yes
|
Community Planning:
|
|
– Planner/Engineer (Land Devel)
|
Yes
|
– Planner/Engineer/Scientist (Natural Hazards)
|
Yes
|
– Engineer/Professional (Construction)
|
Yes
|
– Resiliency Planner
|
No
|
– Transportation Planner
|
Yes
|
Building Official
|
Yes
|
GIS Specialist and Capability
|
Yes
|
Grant Manager, Writer, or Specialist
|
Yes
|
Warning Systems/Services:
|
|
– General
|
Yes
|
– Flood
|
No
|
– Wildfire
|
No
|
– Tornado
|
No
|
– Geological Hazards (West Salt Creek Landslide)
|
Yes
|
Other
|
|
Education and Outreach
|
Yes/No
|
---|
Local Citizen Groups That Communicate Hazard Risks
|
Yes
|
Firewise
|
No
|
StormReady
|
Yes
|
Other
|
|
(Res. 61-20, 10-7-20; Res. 32-15, 7-1-15; Res. 05-10, 1-6-10)
The following sections assess the population, structures, critical
facilities and infrastructure, and other important assets in Mesa
County at risk to natural hazards.
(Res. 61-20, 10-7-20; Res. 32-15, 7-1-15; Res. 05-10, 1-6-10)
A critical facility may be defined as one that is essential
in providing utility or direction either during the response to an
emergency or during the recovery operation. Table 9 displays the inventory
of critical facilities in Mesa County. The information is based on
available data from the Northwest All Hazard Emergency Management
Region.
Table 9: Critical Facilities and Infrastructure
|
---|
Facility Type
|
Unincorporated Mesa County
|
Grand Junction
|
Collbran
|
Palisade
|
Fruita
|
DeBeque
|
---|
Ambulance
|
7
|
10
|
3
|
2
|
3
|
2
|
Bridge
|
104
|
27
|
3
|
–
|
6
|
1
|
Dam
|
47
|
1
|
–
|
–
|
–
|
–
|
EOC
|
1
|
–
|
–
|
–
|
–
|
–
|
Communication Towers
|
103
|
52
|
1
|
–
|
2
|
–
|
Fire Station
|
7
|
5
|
1
|
1
|
1
|
1
|
Govt. Building
|
3
|
14
|
1
|
1
|
1
|
1
|
Helicopter Staging
|
–
|
1
|
–
|
–
|
–
|
–
|
911 Communications Center
|
–
|
1
|
–
|
–
|
–
|
–
|
Medical Facility
|
–
|
3
|
–
|
–
|
1
|
–
|
Schools
|
|
|
|
|
|
|
District 51
|
15
|
19
|
1
|
2
|
5
|
1
|
Private
|
2
|
5
|
|
|
|
|
Water – Wastewater
|
2
|
1
|
1
|
1
|
1
|
1
|
College – University
|
–
|
2
|
–
|
–
|
–
|
–
|
Airport
|
1
|
1
|
–
|
–
|
–
|
–
|
Note: Communication towers include cell towers, radio sites
and TV translators. Other facilities in Mesa County, such as locations
that hold concerts, sporting events, and other events that attract
large numbers of people, may also be at higher risk due to concentrations
of people.
|
(Res. 61-20, 10-7-20; Res. 32-15, 7-1-15; Res. 05-10, 1-6-10)
Assessing the vulnerability of Mesa County to disaster also
involves inventorying the natural, historic, and cultural assets of
the area. This step is important for the following reasons:
(a) 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.
(b) 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 is higher.
(c) The rules for reconstruction, restoration, rehabilitation, and/or
replacement are often different for these types of designated resources.
(d) 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.
(Res. 61-20, 10-7-20; Res. 32-15, 7-1-15; Res. 05-10, 1-6-10)
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. A number of natural resources exist in Mesa County,
including wetlands, endangered species, and imperiled plant communities.
(Res. 61-20, 10-7-20; Res. 32-15, 7-1-15; Res. 05-10, 1-6-10)
Wetlands are a valuable natural resource for communities, due
to their benefits to water quality, wildlife protection, recreation,
and education, and play an important role in hazard mitigation. Wetlands
reduce flood peaks and slowly release 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
stream flow regulation is vital. Figure 19 shows the wetlands that
have been identified throughout Mesa County.
Figure 19: Mesa County Wetlands Areas
|
Source: Mesa County GIS
|
(Res. 61-20, 10-7-20; Res. 32-15, 7-1-15; Res. 05-10, 1-6-10)
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. Figure 20 is a map showing habitats for threatened and endangered
species in Mesa County. (Nelson, 2009)
Figure 20: Mesa County Habitats for Threatened and Endangered
Species
|
The Colorado Division of Parks and Wildlife provides the following
information on their website regarding wildlife species found in Mesa
County that have been given special designations, see Table 10.
(Res. 61-20, 10-7-20; Res. 32-15, 7-1-15; Res. 05-10, 1-6-10)
The Colorado Natural Heritage Program (CNHP) tracks and ranks
Colorado’s rare and imperiled species and habitats, and provides
information and expertise on these topics to promote the conservation
of Colorado’s valuable biological resources. The Statewide Potential
Conservation Areas (PCA) map in Figure 21 shows CNHP’s best
estimate of the primary area required to support the long-term survival
of targeted species or natural communities. (About Us: Colorado Natural
Heritage Program, 2009)
Figure 21: Potential Conservation Areas
|
(About Us: Colorado Natural Heritage Program, 2009)
|
(Res. 61-20, 10-7-20; Res. 32-15, 7-1-15; Res. 05-10, 1-6-10)
Figure 22 shows the ecologically sensitive areas in Mesa County
where threatened and endangered species and imperiled natural plant
communities are most likely found.
Figure 22: Mesa County Ecologically Sensitive Areas
|
Source: Mesa County GIS
|
(Res. 61-20, 10-7-20; Res. 32-15, 7-1-15; Res. 05-10, 1-6-10)
Several national and State historic inventories were reviewed
to identify historic and cultural assets in Mesa County:
(a) The National Register of Historic Places is the nation’s official
list of cultural resources. The National Register is part of a national
program to coordinate and support public and private efforts to identify,
evaluate, and protect historic and archaeological resources. Properties
listed include districts, sites, buildings, structures, and objects
that are significant in American history, architecture, archeology,
engineering, and culture. The National Register is administered by
the National Park Service, which is part of the U.S. Department of
the Interior.
(b) The Colorado State Register of Historic Properties is a listing of
the State’s significant cultural resources worthy of preservation.
Properties listed in the Colorado State Register include individual
buildings, structures, objects, districts, and historic and archaeological
sites.
(c) Table 11 lists the properties and districts in Mesa County that are
on the National Register of Historic Places.
Table 11: National Register of Historic Places in Mesa County
|
---|
Property Name
|
City
|
Location
|
Date Listed
|
---|
Colorado National Monument Visitor Center Complex
|
Mesa County
|
Colorado National Monument
|
07/15/2003
|
Colorado River Bridge
|
Mesa County
|
DeBeque Vicinity
|
10/15/2002
|
Clifton Community Center and Church
|
Mesa County
|
Clifton
|
06/30/1982
|
Coates Creek Schoolhouse
|
Mesa County
|
Glade Park
|
02/03/1993
|
Convicts’ Bread Oven
|
Mesa County
|
Molina
|
12/31/1974
|
Crissey, Herbert and Edith, House
|
Palisade
|
218 W. 1st St.
|
05/18/2003
|
Cross Land and Fruit Company Orchards and Ranch
|
Mesa County
|
3079 F Road
|
03/28/1980
|
DeBeque House
|
DeBeque
|
233 Denver Ave.
|
07/28/1995
|
Denver and Rio Grande Western Railroad Depot
|
Grand Junction
|
119 Pitkin Ave.
|
09/08/1992
|
Devils Kitchen Picnic Shelter
|
Mesa County
|
Colorado National Monument
|
04/21/1994
|
Fruita Bridge
|
Mesa County
|
Cty. Rd. 17.50 over Colorado River
|
02/04/1985
|
Fruita Museum
|
Fruita
|
432 E. Aspen
|
10/10/1996
|
Grand Valley Diversion Dam
|
Mesa County
|
8 miles NE of Palisade
|
10/08/1991
|
Handy Chapel
|
Grand Junction
|
202 White Ave.
|
08/19/1994
|
Hotel St. Regis
|
Grand Junction
|
359 Colorado Ave.
|
10/22/1992
|
IOOF Hall
|
DeBeque
|
4th St. and Curtis Ave.
|
03/25/1993
|
Kettle-Jens House
|
Mesa County
|
498 32nd Road
|
05/06/1983
|
Land’s End Observatory
|
Mesa County
|
Land’s End Road, 10 miles W of CO 65
|
02/28/1997
|
Loma Community Hall
|
Mesa County
|
1341 Co. Rd. 13, Loma
|
11/22/1995
|
Margery Building
|
Grand Junction
|
519-527 Main Street
|
02/24/1993
|
North 7th Street Historic Residential District
|
Grand Junction
|
7th St. between Hill and White Aves.
|
01/05/1984
|
Phillips, Harry and Lilly House
|
Fruita
|
798 N. Mesa St.
|
11/13/1997
|
Pipe Line School
|
Mesa County
|
101 16.5 Rd. Glade Park
|
04/29/1999
|
Rim Rock Drive Historic District
|
Grand Junction
|
Colorado National Monument
|
04/21/1994
|
Saddlehorn Caretaker’s House and Garage
|
Grand Junction
|
Colorado National Monument
|
04/21/1994
|
Saddlehorn Comfort Station
|
Grand Junction
|
Colorado National Monument
|
04/21/1994
|
Saddlehorn Utility Area Historic District
|
Grand Junction
|
Colorado National Monument
|
04/21/1994
|
Serpents Trail
|
Grand Junction
|
Colorado National Monument
|
04/21/1994
|
U.S. Post Office
|
Grand Junction
|
400 Rood Ave.
|
01/31/1980
|
Cayton Ranger Station
|
Mesa County
|
White River National Forest, Silt Vicinity
|
04/27/2005
|
Calamity Camp
|
Mesa County
|
Gateway Vicinity
|
06/11/2011
|
TBM Avenger Aircraft N53503
|
Grand Junction
|
780 Heritage Way
|
11/13/2017
|
Stranges Grocery
|
Grand Junction
|
226 Pitkin Ave
|
03/20/2013
|
Dept of Energy Grand Junction Office
|
Grand Junction
|
2591 Legacy Way
|
07/26/2016
|
(National Register of Historic Places, 2020)
|
(d) Table 12 identifies the properties and districts in Mesa County that
are on the Colorado Office of Archaeology and Historic Preservation
site. Those properties listed in Table 11 were also listed on the
State list.
Table 12: Mesa County Properties Listed as Archaeology and Historic
Preservation Sites
|
---|
Property Name
|
City
|
Location
|
Date Listed
|
---|
Stockmens Bank
|
Collbran
|
111 Main St.
|
03/08/1995
|
Circle Park
|
Fruita
|
Fruita Park Sq.
|
05/14/1997
|
Fruita Elementary
|
Fruita
|
325 E. Aspen St.
|
03/10/1993
|
Weckel House
|
Mesa County
|
1620 Hwy. 6 and 50
|
03/13/1996
|
Driggs Mansion
|
Mesa County
|
24505 State Highway 141
|
09/14/2005
|
Grand Junction Country Club
|
Grand Junction
|
2463 Broadway
|
09/13/1995
|
Hurlburt-Knowles House
|
Mesa County
|
1151 13 Rd. Loma
|
08/09/2000
|
Harlow Gravesite
|
Mesa County
|
869 Rapid Creek Rd.
|
09/13/1995
|
Bloomfield Site
|
Mesa County
|
Whitewater Vicinity
|
01/20/1983
|
Coffman House
|
Mesa County
|
4000 US Hwy. 50
|
12/12/2001
|
Land’s End Aboriginal Site
|
Mesa County
|
Land’s End Road
|
03/11/1998
|
Raber Cow Camp
|
Mesa County
|
Land’s End Road
|
03/10/1993
|
(National and State Registers)
|
(Res. 61-20, 10-7-20; Res. 32-15, 7-1-15; Res. 05-10, 1-6-10)
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. Table
13 lists the major employers in Mesa County based on the number of
employees.
Table 13: Major Employers in Mesa County
|
---|
Employer
|
Employees
|
Industry
|
---|
Mesa County School District #51
|
2,785
|
Education
|
St. Mary’s Hospital and Medical Center
|
2,448
|
Healthcare
|
Mesa County
|
1,070
|
Government
|
State of Colorado
|
1,012
|
Government
|
Community Hospital
|
1,000
|
Healthcare
|
VA Medical Center
|
720
|
Healthcare
|
City of Grand Junction
|
652
|
Government
|
Hilltop Community Resources
|
600
|
Healthcare
|
West Star Aviation
|
441
|
Aviation
|
Mind Springs Health
|
433
|
Healthcare
|
HopeWest
|
350
|
Healthcare
|
Strive
|
304
|
Nonprofit
|
Primary Care Partners
|
304
|
Healthcare
|
Family Health West
|
282
|
Healthcare
|
Navarro
|
263
|
Technical/Professional Services
|
United Companies
|
203
|
Manufacturing
|
StarTek, Inc.
|
203
|
Telecommunications
|
Capco, Inc.
|
200
|
Manufacturing
|
Union Pacific Railroad
|
175
|
Transportation
|
Coors Tek, Inc.
|
150
|
Manufacturing
|
The Daily Sentinel
|
146
|
Media
|
Reynolds Polymer Technology
|
125
|
Manufacturing
|
Mantey Heights Rehab and Care
|
100
|
Healthcare
|
(Data and Demographics: Grand Junction Economic Partnership,
2020)
|
(Res. 61-20, 10-7-20; Res. 32-15, 7-1-15; Senate Bill 11-265, 6-6-11; Res. 05-10, 1-6-10)
This section through GJMC §
42.08.530 describe overall vulnerability and identify structures and estimate potential losses to buildings, infrastructure, and critical facilities located in identified hazard areas. This assessment was limited to the hazards that were considered moderate or high in planning significance, based on HMPC input and the hazard profiles. Hazards that ranked as “low significance” are not included in the vulnerability assessment. These include the following: expansive soils, hailstorm, land subsidence, and tornado.
Many of the identified hazards, particularly weather related
hazards, affect the entire planning area, and specific hazard areas
cannot be mapped geographically. For those hazards, which include
drought, lightning, and winter weather, the vulnerability is mainly
discussed in qualitative terms because data on potential losses to
structures is not available.
(Res. 61-20, 10-7-20; Res. 32-15, 7-1-15; Res. 05-10, 1-6-10)
Mesa County’s vulnerability to avalanches is moderate
due to the historical events where loss of life has occurred. Thousands
of people are exposed to avalanche risk in Mesa County every winter
and spring due to the recreational use of backcountry areas. Motorists
along highways are also at risk of injury or death if avalanches sweep
across roadways.
(a) Existing Development.
Mesa County does not have comprehensive
information or mapping of avalanche hazard areas, therefore limiting
available data on specific structures at risk or estimate of potential
losses to structures.
(b) Future Development.
Based on historic avalanche activity
and lack of anticipated development in backcountry areas, there are
no immediate plans to map avalanches in Mesa County.
(Res. 61-20, 10-7-20; Res. 32-15, 7-1-15; Res. 05-10, 1-6-10)
Mesa County has a considerable amount of high hazard dams; if
a failure of one of these high hazard dams occurred, it would result
in loss of life. There is no specific evidence at the time this plan
was written to indicate a failure of any dams in Mesa County.
Vulnerability to dam failure is greatest on the Grand Mesa where
most of the dams are located and specifically the Town of Collbran
which is downstream from many of the dams. A catastrophic dam failure
would challenge local response capabilities and require evacuations
to save lives. Impacts to life safety will depend on the timely warning
of people in the area. Without immediate warning, loss of life could
result as well as potentially catastrophic effects to roads, bridges,
and homes.
(a) Existing Development.
The Mesa County Department of
Emergency Management retains copies of emergency action plans for
all Class I and Class II dams in the County. The Mesa County Emergency
Management Office has also worked with the Grand Junction Regional
Communications Center to identify potential evacuation areas if a
dam failure were to occur that is built into the reverse 911 system
for notification purposes. Due to ongoing security concerns of the
dam operators, Mesa County Emergency Management requests that inundation
maps not be made part of this public planning process.
(b) Future Development.
Efforts to map out additional evacuation
areas that would be inundated in the event of a dam failure will continue
with the Grand Junction Regional Communications Center. The County
and towns should consider the dam failure hazard when permitting development
downstream of the Class I and Class II dams.
(Res. 61-20, 10-7-20; Res. 32-15, 7-1-15; Res. 05-10, 1-6-10)
Drought has been a significant issue in Mesa County. It is the
one hazard that cannot be controlled yet it has devastating effects
that can last for several years. Drought has several impacts to Mesa
County including but not limited to: air quality, wildfires, reduction
of tourism and recreation activities, and damage to the agriculture
industry.
(a) Existing Development.
The impacts from drought are nonstructural
and generally affect the economy and environment the most. A drought
event normally does not impact structures and it can be difficult
to identify specific hazard areas. Many of the towns use public education
efforts to encourage water conservation during the summer months.
(b) Future Development.
Vulnerability to drought will increase
as population growth increases, putting more demands on existing water
supplies. Future water use planning should consider increase in population
as well as potential impacts of climate change.
(Res. 61-20, 10-7-20; Res. 32-15, 7-1-15; Res. 05-10, 1-6-10)
Past earthquake activity in Mesa County has been minimal and
most earthquake activity has low magnitude and severity. Earthquake
data in Mesa County is limited but some historical information is
available through Colorado Mesa University.
(a) Existing Development.
By using data from the HAZUS-MH
software, information on potential economic and social losses due
to an earthquake in Mesa County can be determined. This particular
information produces “what if” scenarios (e.g., determines
what would happen if an earthquake of a certain magnitude occurred
on a particular fault). The earthquake magnitudes used for each fault
were the “maximum credible earthquake” as determined by
the U.S. Geological Survey.
There are 16 Quaternary aged faults identified by the USGS in
Mesa County. There are innumerable older faults that have been identified
and presumably older faults which remain hidden from view. The Quaternary
aged faults are associated with the Uncompahgre Plateau. The Uncompahgre
Plateau extends from Grand County, Utah, northwest of Grand Junction
to near the Town of Ridgway, Colorado. The Uncompahgre has as much
as 640 meters of uplift. The faults associated with the uplift are
in two groups, bordering both the southwest flank and northeast flank
of the uplift.
The northeast flank of the Uncompahgre Plateau, near Grand Junction,
contains the Redlands Fault complex. This fault shows as much as 240
meters of displacement and can be seen most vividly in the Colorado
National Monument. The Colorado Geological Survey has estimated that
the largest earthquake possible on the Western Slope of Colorado is
magnitude 6.5.
(b) Using the HAZUS-MH program, Emergency Management staff and a Colorado
Mesa University faculty member designed and analyzed the following
earthquake scenario on the Bridgeport/Cactus Park fault complex in
southern Mesa County:
(1) Type: Deterministic, arbitrary.
(2) Attenuation Function: Western U.S. Shallow Crustal Event –
Nonextensional.
(4) Epicenter.
(i) Latitude 38.875, Longitude -108.438.
(5) Fault Mechanism: Reverse Slip.
(6) Rupture.
(i) Subsurface Length: 5.88844 kilometers.
(ii)
Surface Length: 4.02717 kilometers.
(iii)
Orientation: 120 degrees.
(iv)
Dip Angle: 75 kilometers.
While this is not the worst-case scenario for an
earthquake event in Mesa County, it is believed to be a more plausible
scenario (Wolny, Martsolf, 2009). Figure 23 provides an illustration
of potential ground acceleration from this scenario.
|
Figure 23: HAZUS Earthquake Scenario
|
Figure 24 shows how far reaching this type of earthquake would
be felt in Mesa County and Figure 25 identifies the area with displaced
homes.
|
Figure 24: Bridgeport Earthquake Ground Motion
|
Figure 25: Bridgeport Earthquake Scenario, Displaced Homes
|
(c) In calculating building damage associated with this type of earthquake,
the following HAZUS definitions were used:
(1) Slight damage. Small plaster or gypsum board cracks
at corners of doors and window openings and wall-ceiling intersections,
small cracks in masonry chimneys and masonry veneer.
(2) Moderate damage. Larger plaster or gypsum board
cracks at corners of door and window openings; small diagonal cracks
across shear wall panels exhibited by small cracks in stucco and gypsum
wall panels; large cracks in brick chimneys; toppling of tall masonry
chimneys.
(3) Extensive damage. Large diagonal cracks across shear
wall panels or large cracks at plywood joints; permanent lateral movement
of floors and roof; toppling of most brick chimneys; cracks in foundations;
splitting of wood sill plates and/or slippage of structure over foundations;
partial collapse of room-over garage or other soft-story configurations;
small foundation cracks.
(4) Complete damage. Structure may have large permanent
lateral displacement, may collapse, or be in imminent danger of collapse
due to cripple wall failure or the failure of lateral load resisting
system; some structures may slip and fall off the foundations; large
foundation cracks.
Table 14 provides an estimated number of buildings damaged throughout
Mesa County and the extent of damage to the various types of structures
using this scenario.
|
Table 14: Estimated Building Damage from Earthquake
Number of Buildings
|
---|
|
No Damage
|
Slight Damage
|
Moderate Damage
|
Extensive Damage
|
Complete Damage
|
Total
|
---|
Wood
|
28,677
|
2,296
|
384
|
25
|
0
|
31,382
|
Steel
|
177
|
10
|
5
|
1
|
0
|
193
|
Concrete
|
367
|
27
|
10
|
1
|
0
|
405
|
Precast
|
192
|
16
|
13
|
3
|
0
|
224
|
Reinforced Masonry
|
3,234
|
202
|
133
|
20
|
0
|
3,589
|
Manufactured Home
|
2,086
|
295
|
156
|
16
|
0
|
2,553
|
Total
|
34,733
|
2,846
|
701
|
66
|
0
|
38,346
|
Table 15 identifies the possible economic loss throughout Mesa
County due to the number of damaged or destroyed buildings as a result
of this type of earthquake.
|
Table 15: Direct Economic Loss
|
---|
Capital Stock Losses
|
---|
Structural Damage Loss
|
Nonstructural Damage Cost
|
Contents Damage Cost
|
Inventory Loss
|
---|
$11,819,000.00
|
$37,667,000.00
|
$15,472,000.00
|
$539,000.00
|
Income Losses
|
---|
Relocation Loss
|
Capital Related Loss
|
Wage Losses
|
Rental Income Loss
|
$315,000.00
|
$2,977,000.00
|
$3,944,000.00
|
$4,520,000.00
|
Total Loss
|
---|
$65,497,000.00
|
(d) Much of the County’s recent development has building codes
in place which reduce the risk of structural damage. However, historical
buildings constructed of unreinforced masonry are most vulnerable
to seismic ground shaking. Downtown Grand Junction is one of the areas
most vulnerable to a seismic event due to older construction.
Similar to calculating damage to buildings, the analysis also
allows us to estimate possible injuries sustained throughout Mesa
County during a 5.5 magnitude earthquake. This data is shown in Table
16. HAZUS injury definitions are defined as the following:
(1) Severity 1. Injuries requiring basic medical aid
without requiring hospitalization.
(2) Severity 2. Injuries requiring a greater degree
of medical care and hospitalization, but not expected to progress
to a life-threatening status.
(3) Severity 3. Injuries that pose an immediate life-threatening
condition if not treated adequately and expeditiously. The majority
of these injuries are the result of structural collapse and subsequent
collapse or impairment of the occupants.
(4) Severity 4. Instantaneously killed or mortally injured.
Table 16: Possible Injuries Sustained in Earthquake
Injury Severity Level
|
---|
Casualties at 2:00 a.m. event
|
Severity 1
|
Severity 2
|
Severity 3
|
Severity 4
|
Total
|
---|
Commuting
|
0
|
0
|
0
|
0
|
0
|
Commercial
|
0
|
0
|
0
|
0
|
0
|
Educational
|
0
|
0
|
0
|
0
|
0
|
Hotels
|
0
|
0
|
0
|
0
|
0
|
Industrial
|
0
|
0
|
0
|
0
|
0
|
Other – Residential
|
7
|
1
|
0
|
0
|
8
|
Single-Family
|
14
|
2
|
0
|
0
|
16
|
Total Casualties – 2:00 a.m.
|
21
|
3
|
0
|
0
|
24
|
Casualties at 2:00 p.m. event
|
Severity 1
|
Severity 2
|
Severity 3
|
Severity 4
|
Total
|
---|
Commuting
|
0
|
0
|
0
|
0
|
0
|
Commercial
|
13
|
2
|
0
|
0
|
15
|
Educational
|
3
|
0
|
0
|
0
|
3
|
Hotels
|
0
|
0
|
0
|
0
|
0
|
Industrial
|
2
|
0
|
0
|
0
|
2
|
Other – Residential
|
1
|
0
|
0
|
0
|
1
|
Single-Family
|
3
|
0
|
0
|
0
|
3
|
Total Casualties – 2:00 p.m.
|
22
|
2
|
0
|
0
|
24
|
Casualties at 5:00 p.m. event
|
Severity 1
|
Severity 2
|
Severity 3
|
Severity 4
|
Total
|
---|
Commuting
|
0
|
0
|
0
|
0
|
0
|
Commercial
|
10
|
1
|
0
|
0
|
11
|
Educational
|
0
|
0
|
0
|
0
|
0
|
Hotels
|
0
|
0
|
0
|
0
|
0
|
Industrial
|
1
|
0
|
0
|
0
|
1
|
Other – Residential
|
3
|
1
|
0
|
0
|
4
|
Single-Family
|
5
|
1
|
0
|
0
|
6
|
Total Casualties – 5:00 p.m.
|
19
|
3
|
0
|
0
|
22
|
(e) Future Development.
All jurisdictions within Mesa County
have adopted building codes. Building codes substantially reduce the
costs of damage to future structures from earthquakes. It is highly
recommended that a specific study be done on the liquefaction hazards
found within the Grand Valley. This is the single most important unknown
in assessing the vulnerability of earthquakes in Mesa County.
(Res. 61-20, 10-7-20; Res. 32-15, 7-1-15; Senate Bill 11-265, 6-6-11; Res. 05-10, 1-6-10)
Floods affect most of the communities in Mesa County and will
continue to occur in the future. Floods can be critical in their magnitude
and may cause deaths and damage to property and infrastructure.
(a) Existing Development.
In 2005, Mesa County entered FEMA’s
map modernization program to develop digital flood insurance rate
maps (DFIRMS) in partnership with State and federal agencies. Mesa
County has received a copy of the preliminary copies of the Digital
Flood Insurance Rate Map (DFIRM) and Flood Insurance Study (FIS) report.
Samples of DFIRMS are included in the community profiles for participating
jurisdictions. A comprehensive collection of DFIRMS can be viewed
on Mesa County’s website.
Analysis was done for each community in Mesa County to determine
the proportion of value of buildings in the hazard areas that were
identified by the HMPC. The GIS system was used by selecting parcels
that have their center within the city or town limits, then by making
a subselection of parcels that have their center within the areas
subject to flooding. Structure value is based on the actual value
of improvements. Specific information regarding flood losses is identified
in the jurisdiction’s annex.
(b) Floodplain Management.
The purpose of the Mesa County
Floodplain Management program is to assist property owners with any
improvements in the floodplain. The County’s goal is to help
minimize property damage to residents of Mesa County during flood
events. Mesa County wants to ensure that life, property including
natural resource values, and/or new improvements are safe during flood
events and that any structures or improvements in the floodplain will
not cause additional drainage problems.
Regulations are in place to ensure that proposed improvements
will not cause flooding problems upstream and/or downstream. Every
manmade structure or improvement constructed within the floodplain
area requires a floodplain development permit prior to beginning construction.
A floodplain development permit authorizes a specific activity within
the regulatory floodplain while minimizing the likelihood of property
damage to buildings or improvements in the event of a flood. (County,
Mesa County Public Works, Stormwater Management, 2009)
The National Flood Insurance Program (NFIP) is a federal program
enabling property owners in participating communities to purchase
insurance as a protection against flood losses. A jurisdiction’s
eligibility to participate is premised on their adoption and enforcement
of state and community floodplain management regulations intended
to prevent unsafe development in the floodplain, thereby reducing
future flood damages. Thus, participation in the NFIP is based on
an agreement between communities and the federal government. If a
community adopts and enforces a floodplain management ordinance to
reduce future flood risk to new construction in floodplains, the federal
government will make flood insurance available within the community
as a financial protection against flood losses. Currently all of the
communities in and including Mesa County participate in the National
Flood Insurance Program.
(c) Future Development.
Management of storm water is important
to the communities in Mesa County. As mandated under the Clean Water
Act, the U.S. Environmental Protection Agency has developed a National
Pollutant Discharge Elimination System storm water permitting program.
Phase II of this program addresses smaller urbanized areas, such as
the Grand Valley. Currently the jurisdictions in Mesa County have
identified areas where Phase II regulations are to be implemented,
requiring storm water construction permits. (County, Mesa County Public
Works, Stormwater Management, 2009)
(Res. 61-20, 10-7-20; Res. 32-15, 7-1-15; Res. 05-10, 1-6-10)
In Mesa County, vulnerability to landslides primarily occurs
along roadways, where the hazard could cause deaths or injuries. Road
closures due to landslide events also affect the County economically.
(a) Existing Development.
Under the Mesa County Land Development
Code, Chapter 7, any proposed land use or development must identify
hazard areas, i.e., floodplains, drainage areas, steep slope areas,
geological fault areas, and other areas hazardous to life or property.
Such proposals will require an evaluation to determine the degree
to which the proposed activity will:
(1) Expose any person, including occupants or users of the proposed use
or development, to any undue natural hazard.
(2) Create or increase the effects of natural hazard areas or other improvements,
activities or lands.
(3) Impact the natural environment and be unduly destructive to the natural
resources of an area.
Regulations also require proposed land uses to address soil,
erosion, and surface geologic characteristics of the development site
through proper design, engineering and construction. (County, Mesa
County Planning Division, 2014)
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Potential losses for the landslide areas in Mesa County were
estimated using Mesa County GIS and assessor’s data and were
examined in terms of values and critical facilities at risk. Detailed
information pertaining to specific jurisdictions is found in that
jurisdiction’s community profile.
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(b) Future Development.
The severity of landslide problems
is directly related to the extent of human activity in hazard areas.
Adverse effects can be mitigated by early recognition and avoiding
incompatible land uses in these areas or by corrective engineering.
The mountainous topography of the County presents considerable constraints
to development, most commonly in the form of steep sloped areas. These
areas are vulnerable to disturbance and can become unstable. Most
of these areas are adjacent to roadway systems that are heavily used.
Continued adherence to the Land Development Code is necessary.
(Res. 61-20, 10-7-20; Res. 32-15, 7-1-15; Res. 05-10, 1-6-10)
Lightning events are likely to occur throughout Mesa County
and can result in deaths and destruction of property. Consequences
of lightning may have destructive effects on power and information
systems. Failure of these systems would have cascading effects throughout
the County and could possibly disrupt other critical infrastructure
such as water treatment facilities. Because lightning can occur anywhere
in the County, data was not available to identify specific structures
at risk or estimate potential losses.
(Res. 61-20, 10-7-20; Res. 32-15, 7-1-15; Res. 05-10, 1-6-10)
(a) Existing Development.
Winter storms can create significant
public safety concerns and cause significant impacts to the local
economy due to a disruption in the transportation of goods. On occasion,
winter storms can overwhelm snow removal efforts, transportation,
livestock management and business and commercial activities.
From previous events, Mesa County Emergency Management staff
has identified the County’s elderly population as a significantly
vulnerable population during winter storms especially when utility
outages are associated with winter storms.
(b) Future Development.
Population growth in the County
will increase potential problems with traffic and snow removal, thereby
putting pressure on local governments and emergency services. The
Grand Valley does not typically experience significant winter storms;
however, it has experienced utility outages associated with severe
weather. Future efforts should be made to identify populations at
risk and determine special needs.
(Res. 61-20, 10-7-20; Res. 32-15, 7-1-15; Res. 05-10, 1-6-10)
(a) Existing Development.
Past mitigation projects include
a detailed, on the ground, wildfire hazard risk assessment for approximately
450 structures including private residences and outbuildings within
the jurisdictions of Lower Valley Fire Protection District, Grand
Junction Rural Fire Protection District and unincorporated Mesa County.
Each structure was evaluated based on potential fuels, slope, aspect,
fire disturbance regimes, access/egress, water supply, and structure
ignitability. This data was compiled and incorporated into the County’s
GIS system.
The GIS data shows structures that have been rated as to overall
risk of wildfire, as well as those areas deemed most appropriate for
wildland fire hazard mitigation efforts on both federal and non-federal
lands within this area. This information is used to aid local fire
departments and federal agencies in preparing fuels mitigation projects
and preplanning fire prevention and protection strategies. This assessment
also serves as the basis for public information and education efforts
directed primarily by the Colorado State Forest Service and participating
jurisdictions to encourage private property owners to participate
in Firewise and other mitigation efforts to protect their property.
Mesa County Land Development Code specifically addresses development
standards in hazard areas. All new development located on lands rated
as medium or higher wildfire hazard shall be developed using defensible
spacing standards. (County, Mesa County Planning Division, 2014)
(b) Future Development.
Many areas in Mesa County now have
an increased wildfire threat in areas where fire was not a problem
in the past. This is due to a combination of irrigation and the introduction
of nonnative plants. Nonnative tamarisk and Russian olive have invaded
drainage areas. Excess undrained irrigation water has created thick
unbroken stands of vegetation throughout the Grand Valley. These stands
of tamarisk and Russian olive burn readily and pose a threat to homes
and other structures. (Paul, 2009)
Additional wildfire assessments need to be conducted across
Mesa County. Several areas are at significant risk to wildland fire
and more education of property owners on how to create a defensible
space around their homes and other structures is needed. Once the
assessments have been completed, on the ground efforts to create defensible
spacing or thinning of areas with substantial overgrowth need to be
completed.
(Res. 61-20, 10-7-20; Res. 32-15, 7-1-15; Res. 05-10, 1-6-10)
Between 2015 to 2019, there were 422 new subdivision plats recorded
in Mesa County accounting for 3,558 subdivision lots. These new subdivision
lots are distributed as detailed as follows:
(a) City of Grand Junction: 2,332.
(f) Unincorporated Mesa County: 770.
The number of building permits issued for the unincorporated
area of Mesa County is reflected in the following table.
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2015
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2016
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2017
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2018
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2019
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Commercial Permits
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8
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5
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11
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11
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6
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Residential Permits
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190
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158
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184
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272
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232
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Individual community profiles contain additional information
on new development within each respective community.
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(Res. 61-20, 10-7-20; Res. 32-15, 7-1-15)