FLOOD08745

• County: Statewide
• Community: Statewide
• Basin: Statewide
• Title: Colorado Flood Hazard Mitigation Plan
• Date: 12/1/1999
• Prepared For: State of Colorado
• Prepared By: Kistner and Associates
• Floodplain - Doc Type: Flood Mitigation/Flood Warning/Watershed Restoration

Colorado Flood Hazard Mitigation Plan - 1999

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ence with Buffalo Creek, and several other tributary
streams in the area, Two lives were lost as a direct
result of the flooding. Roads, bridges, water lines, and
other utility lines were damaged or destroyed. Numer-
ous homes, outbuildings, and vehicles were damaged
or destroyed, as well, A large quantity of sediment and
debris was carried from the watershed and depostted
along the affected stream reaches,

Although the geographic area affected was smaller
than in some other floods, the July 12 Buffalo Creek
flood event was truly a disaster. Other smaller scale
floods have occurred in Buffalo Creek between June
and September 1996, as well,

Peak discharges for the July 12 event for the North
Fork, Buffalo Creek, Sand Draw, and other tributaries
were estimated by the Colorado Water Conservation
Board (CWCB) and the USGS, The CWCB obtained
detailed surveyed cross-sections on the North Fork of
the South Platte River, Sand Draw, and Buffalo Creek,
The preliminary discharge estimates, along with pub-
lished FEMA 100-year flow values, are shown in Fig-
ure 2.9, The estimated flow rates on July 12 range
from 4 to 25 times the published FEMA 100-year flow
values. Obviously, the Buffalo Creek flash flood pro-
duced enormous flow magnttudes and was extremely
dangerous,

1999 Landslide Events - Landslides occurred in sev-
erallocations throughout the stale due to heavy rains.
EI Paso County, and the ctties within suffered dam-
ages from land movement. One project application for
DR-1276-CO includes acquisttion of structures dam-
aged from land movement (Manitou Springs), In July
1999, several locations along Interstate 70 (1-70) were
closed briefly due to land movements,

2.4 Risk Information
To reduce the community's vulnerability to hazards,
some knowledge of the riskllhreat must exist. Thus,
hazards assessment has two important components:

1, Hazard Identfflcation - What are the hazards
that pose a threalto the community or a particu-
lar segment of the population? What is their ex-
pected magnitude? How frequently could they
be expected to occur? Where are they likely to
occur?

2, Vulnerabllfty AnalysIs - What Is the risk from
the threat? What are the likely impacts? What
are the economic, social, and polttical ramifica-
tions of these impacts?

In most Colorado communities, substantial work has
already been completed on a hazards assessment,
and maps portraying these risks are readily available,
This is an integral step in the emergency planning

process. Hazards assessment is the foundation upon
which the local Emergency Operations Plan (EOP) is
built. It is also the foundation for hazard mttigation
planning. As mentioned earlier in this chapter, one of
the recommendations of this plan is to begin to inven-
tory the structures and people in Colorado'S floodplain,
This inventory, when completed, will enable planners
at the state and local level of governments to plan and
mttigate the flood hazard,

A hazards assessment provides the information that
identifies the need to mnigate, as well as the abiltty to
accurately focus mitigation efforts on a particular prob-
lem area. However, simply identifying vulnerability
from an identified risk does not guarantee that any ac-
tion will be undertaken to mitigate that situation, Thus,
a crnical component necessary to mitigate the impacts
of hazards is a determination of acceptable risk.
When vulnerability to a hazard risk is determined to be
at an acceptable level, mttigation activtties are not pur-
sued. However, when communities determine that the
vulnerability to a given risk is too greal to chance (a
determination of unacceptable risk), mttigation Is pur-
sued,

This concept of acceptable risk is central to the com-
munity's determination as to whether mttigation is un-
dertaken or not, This determination is typically an-
swered based on community values being combined
with technical information. Hazards assessments allow
communtties to focus on hazard mttigation planning
needs, However, implementation of mttigatlon meas-
ures will only occur following the public's acceptance of
both the problem and the solution. This requires a de-
termination that there is unacceptable risk,

To sum up, the hazard mttigation planning process
begins wtth the five preliminary steps relating to haz-
ards assessment. First, the hazards affecting the juris-
diction must be identified. Second, the community's
vulnerabiltty to those hazards must be determined,
Third, a determination of whether that vulnerability
constitutes an unacceptable risk must be made,
Fourth, if an unacceptable risk exists, it must be com-
municated to those who are in the posttion to effect tts
change. Fifth, the people receiving this risk information
must agree that the risk is unacceptable, that there are
viable solutions to the problem, and that mttigation
ought to be undertaken as a means of bringing about
these solutions.

The term "hazard vulnerability" implies a relationship
between human population concentrations and their
respective potential for experiencing a hazard occur-
rence. Population expansion by ns very nature de-
creases available land area, The resuit, then, is a likely
increase in the probabilny of some Colorado commu-
nity during its history sustaining an impact from a haz-

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Chapter 2 - 12

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