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Colorado Flood Hazard Mitigation Plan - 1999 ence wrth 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 deposited 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 10o-year flow values, Obviously, the Buffalo Creek flash flood pro- duced enormous flow magnitudes and was extremely dangerous, 1999 Landslide Events - Landslides occurred in sev- eral locations throughout the state due to heavy rains, EI Paso County, and the cities within suffered dam- ages from land movement. One project application for DR-1276-CO includes acquisition 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 riskithreat must exist. Thus, hazards assessment has two important components: 1, Hazard Identification - What are the hazards that pose a threat to 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, Vulnerability Analysis - What is the risk from the threat? What are the likely impacts? What are the economic, social, and political ramifica- tions of these impacts? In most Colorado communrties, 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 mitigation pianning, 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 mitigate the flood hazard, A hazards assessment provides the information that identifies the need to mitigate, as well as the ability to accurately focus mitigation efforts on a particular prob- lem area, However, simply identifying vulnerability from an iden@ed risk does not guarantee that any ac- tion will be undertaken to mitigate that situation, Thus, a critical component necessary to mitigate the impacts of hazards is a determination of ecceptable risk. When vulnerability to a hazard risk is determined to be at an acceptable level, mitigation activities are not pur- sued, However, when communities determine that the vulnerability to a given risk is too great to chance (a determination of unacceptable risk), mitigation is pur- sued, This concept of acceptable risk is central to the com- munity's determination as to whether mitigation is un- dertaken or not This determination is typically an- swered based on community values being combined with technical information, Hazards assessments allow communities to focus on hazard mitigation planning needs, However, implementation of mitigation 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 mitigation planning process begins with the five preliminary steps relating to haz- ards assessment. First, the hazards affecting the juris- diction must be identified, Second, the community's vulnerability to those hazards must be determined. Third, a determination of whether that vulnerability constitutes an unacceptable risk must be made, Fourth, it an unacceptable risk exists, it must be com- municated to those who are in the position to effect its 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 mitigation 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 its very nature de- creases available land area, The result, then, is a likely increase in the probability of some Colorado commu- nity during its history sustaining an impact from a haz- 12/23/99 10:00 PM Chapter 2 -12