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, , FLOOD HISTORY INVESTIGATIONS AND ANALYSIS flooding along Cripple Creek and tributaries can occur as a result of local storms on watersheds above the City. An example of local flooding is the flood of June 18, 1965. This particular event was not an extreme flood but it did produce street and road damages as well as damage to commercial property such as the Cripple Creek Market where water flooded in from both the roof and the street. Water eight inches deep was measured in the vacant eastern portion of the market, most of which came from Second Street. Nearly all business buildings had slight water damage caused by either hail punctures in roofs or from street runoff. Interoretation and Use of Reoort A. Frequency and Discharge The 10-, 25-, 50-, and laO-year flood events are used as the flood ~requ7ncies for ~his floo~ plain analysis. Thus, the data developed ~n th~s repor~ w~l~ be su~~able not only for regulation purposes, and H.B. 1041 des~gnat~on but ~s also consistent with Federal Insurance Administration flood insurance studies conducted by the Federal Emergency Management Agency. Precipitation records are incomplete however there are data for three periods; 1896 to 1918 and 1939 to 1952 for the Cripple Creek location and from 1948 to 1971 for the Cripple Creek 9 NW location. The greatest one day recorded rainfall occurred in 1904 (3.13 inches). There were eight occurrance of 2.0 or more inches of rainfall during the period of record. The June 1965 event was not Officially measured although there were some newspaper accounts suggesting several inches of rain and hail produced the flooding previously discussed. These various flood events have an average occurrence of once in the number of years as indicated. For example, the lOa-year flood occurs, on the average, once in a 100-year period, and has a one percent chance of being equaled or exceeded in any given yoar. The particular uses for the various flood events in addition to those stated above are as follows: la-year, 25-year and 50-year Flood Events Information regarding these lower frequency floods is especially useful for future engineering studies and land use planning purposes relat7d to minor road systems, minor channel improvements, the lccat~on of parks and recreational facilities, agricultural lands, and appurtenant.structu:es. The use of the low~r frequency floods ~ay be cons~dered ~n plann~ng flood prevention proJects to protect agricultural areas, or other property where risk to life is not d factor. lOO-year Flood Event The lOa-year flcod event may be used in lieu of lower frequencies for engineering design purposes where greater security from structur~ failure is desired. However, the most important use of the lOO-year flood eVent lies in flood plain management and land use planning as set forth in the state statutes. The State of Colorado and the Federal Government consider Lha lOO-ye<lr frequency flood <IS the flood event to be us<.!d i.n designi~g and protecting structures and dwellings for human occupat~on. Therefore, all flood plain regulations are based upon the lOa-year flood.