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<br />Examples of stmctural deficiencies include seepage through the embankment, pIplllg <br />along internal conduits, erosion, cracking sliding, overturning, rodent tunneling, or other <br />weakness in the stmcture. Old age is often at the root of stmctural deficiencies. Seismic <br />activity in Colorado has recently been recognized as a potential source of stmctural <br />problems due to liquefaction of sand layers in the embankment of a dam. <br /> <br />The mechanics of a stmctural failure depends on the type of dam and the mode of failure. <br />Dam failure floods due to stmctural deficiencies are characterized by a sudden rise in <br />stream level and relatively short duration similar to a thunderstorm flood. They can <br />occur at any time, but earthen dams appear to be most susceptible to stmctural failure <br />during the fall and spring freezing and thawing cycles. <br /> <br />PROFILING FLOOD HAZARDS <br /> <br />The relationship between flood hazards and population identifies patterns of risk. Such <br />relationships are not new to Colorado. Flooding has occurred here long before people <br />settled in high-risk areas. Risk grows from the increasingly close association between <br />natural phenomena and a growing population. <br /> <br />People become vulnerable to hazards when they choose (knowingly or unknowingly) to <br />live near the areas where these extreme events occur. Vulnerability is also related to <br />preparedness. People who prepare for the occurrence of an extreme event are less <br />vulnerable to it than those who do not. The vulnerability of Colorado's population is <br />rooted in a relationship between the occurrences of extreme events, the proximity of <br />people to these occurrences, and the degree to which these people are prepared to cope <br />with these extremes of nature. <br /> <br />Presently, flood prone areas have been identified in 268 cities and towns and in all of the <br />64 counties in Colorado. Using information supplied from local units of government, <br />there are estimated to be approximately 250,000 people now living in Colorado's <br />floodplains. The CWCB estimates that approximately 65,000 homes and 15,000 <br />commercial and industrial business stmctures are located in Colorado's floodplains. <br />Designation of floodplains in Colorado for floodplain management activities is related to <br />the 100-year flood event. Cumulative flood losses from the turn of the century to 2006 <br />from the state's most damaging floods are over $5.5 billion (2007 dollars). <br /> <br />15 <br />