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ENGINEERING METHODS . Hvdroloe:ic Analvsis . . Hydrology information for the streams within the Town of Monument with approximate floodplain delineations on the FIRM panels has been estimated in accordance with procedures described in the CWCB's Guidelines for Determining lOO-Year Flood Flows for Approximate Floodplains (Guidelines), Depending on the drainage area of the upstream (contributing) watershed, the 100- year flows can be estimated either by using a regression equation included in the Guidelines, or by using a USGS publication approved in the Guidelines, A copy of the Guidelines can be obtained by writing to the Colorado Water Conservation Board, Flood Control and Floodplain Management Section, 1313 Sherman Street, Room 721, Denver, Colorado, 80203, The 100-year flow for the streams in the Town of Monument, mapped by approximate techniques, cannot be estimated by utilizing the regression equation for Arkansas River Basin, subregion Ark- 4b. The equation developed by the CWCB is applicable to watersheds with an upstream drainage area greater than or equal to 4 square miles and less than or equal to 75 square miles, Only one out of the eleven hydrology points listed below has an upstream drainage area that falls within that range, Therefore, the Guidelines regression was not used for any of the approximate floodplains in the Town of Monument For streams with drainage areas smaller than 4 square miles, the U,S, Geological Survey publication, Techniques For Estimating Regional Flood Characteristics of Small Rural Watershed in the Plains Region of Eastern Colorado can be used to supplement the Guidelines. The USGS publication can used for stream reaches with upstream watersheds larger than a lower limit of 0.25 to 0.5 square mile and smaller than an upper limit of25 square miles, Figure I, presented in the Appendix at the end of this report, displays the portion of the Arkansas River basin that includes Subregion Ark-4b, The regression curve for Subregion Ark-4b is also included in the Appendix as Figure 2. Figure 3 displays the regression curve prepared by the U.S, Geologic Survey. Table I displays the 100-year peak flows estimated by using the US,G,S, regression equation, Information for Crystal and Dirty Woman Creeks was derived from detailed studies found in FEMA's March 17, 1997 FIS for El Paso County and Incorporated Areas,