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. . . PREFACE This hydrology addendwn is part of a program by the Colorado Water Conservation Board (CWCB) to make approximate floodplain maps prepared by the Federal Emergency Management Agency (FEMA) easier for local governments to use. This CWCB report provides limited engineering information to support the approximate delineations on the maps. The official floodplain information for the City of Colorado Springs is the Flood Insurance Study (FIS) with its associated Flood Insurance Rate Maps (FIRMs), dated December 18, 1986, as modified and supplemented by the Revised Flood Insurance Study dated March 2, 1989, There are two other Revised FIS' for Colorado Springs, one dated 1990 and the other dated 1992, but they are not addressed in this Hydrology Addendum. The only new floodplain information that they include is supported by detailed hydrologic analyses, so no Hydrology Addenda will be needed for those two reports. The original FIS and the Revised FIS were prepared by FEMA, and they include engineering information for those streams that were studied in detail. However they do not include any engineering information to describe basis of the approximate floodplain mapping. The initial purpose of this Hydrology Addendwn, therefore, is to provide the city with limited supporting information for the approximate floodplain delineations, The addendwn includes a description of a hydrologic analysis that was performed for the city as part of the CWCB' s technical assistance program. The hydrologic analysis is consistent with the FEMA mapping. In addition, the addendwn gives the city some basic information about floodplain management and it gives some alternatives that could be considered in formulating and implementing its floodplain management objectives. A second function of this report is to assure that the original FIS and the Revised FIS meet the basic technical requirements for designation and approval by the CWCR Without a hydrologic analysis, the approximate floodplain information in the Colorado Springs FIS' cannot qualify for CWCB designation. Colorado statutes require that local governments obtain from the CWCB the designation and approval of floodplain information for its use in regulato!)' purposes. This addendwn provides a means for the FIS' to meet that statuto!)' objective. The FIS' were prepared prior to the completion of a CWCB docwnent entitled Guidelines for Determining 100-year Flood Flows for Approximate Floodplains (Guidelines), The Guidelines provide the necessary hydrologic information in support of the approximate I DO-year floodplain boundaries identified on the Flood Insurance Rate Map (FIRM) panels. The hydrologic information contained in the Guidelines was used in preparing this addendwn and it supports the subsequent designation of the EI Paso County FIS'.