Laserfiche WebLink
<br />1.0 PURPOSE, PROCEDURES, AND USE <br /> <br />1.1 INTRODUCTION <br /> <br />The Colorado Water Conservation Board (CWCB), Flood Control and Floodplain Management <br />Section, performs technical reviews for CWCB designation and approval of floodplain and <br />drainageway studies, Through its process of designation and approval of floodplain studies, the <br />CWCB staff prepares a numbered resolution for each study submitted for Board action, As of <br />December 1998, this program has processed approximately 480 resolutions designating and <br />approving floodplain reports. The resolutions and the accompanying studies are catalogued in the <br />CWCB's library and data base system. <br /> <br />Until the development of these Guidelines for Determining lOO-year Flood Flows for <br />Approximate Floodplains in Colorado (Guidelines), the CWCB had no procedure for determining <br />hydrology values for approximate floodplain mapping. Such approximate mapping could not, <br />therefore, meet CWCB technical requirements for designation and approval. It was decided that a <br />methodology linking the approximate floodplain delineations to existing detailed hydrologic <br />analyses was needed in order to comply with CWCB requirements. <br /> <br />The regression equations included in these Guidelines were prepared using published IOO-year <br />hydrologic information in existing detailed floodplain reports that were already designated or soon <br />to be designated. The CWCB prepared equations for hydrologic drainage area vs. discharge using <br />a best-fit curve regression program, Data points from regional basins were grouped geographically <br />and draft regression equations were developed, These draft equations were tested by graphical <br />interpretation and through standard measures of regression validity. The CWCB staffwill use these <br />regression equations to estimate 100-year peak "flow values for stream reaches that have only <br />approximate floodplain information or no information at all. This process will fulfill the <br />hydrologic requirements for the designation and approval of approximate floodplain information in <br />Colorado, As described later in this document, the regression equations are subject to limitations in <br />their application. For certain applications, a detailed hydrologic and hydraulic analysis will be <br />needed, <br /> <br />Draft versions of the Guidelines were reviewed by the CWCB's Colorado Flood Hydrology <br />Advisory Committee (Committee). The Committee is made up of selected practicing hydrologists <br />and engineers from the public and private sectors. The Committee members included <br />representatives from federal, state, and local agencies, and from consulting engineering firms. <br /> <br />1.1.1 Acknowledgments <br /> <br />Completion of this version of the Guidelines was performed by CWCB staff under the direction of <br />Larry F. Lang, P.E" and was facilitated by the help and guidance from the Colorado Flood <br />Hydrology Advisory Committee, The author wishes to thank the entire Committee along with <br />Brian Hyde and Jim Wieger for their invaluable assistance. <br />I <br />