Laserfiche WebLink
<br />. <br /> <br /> <br />COLORADO STATEWIDE <br />DRAINAGE AND FLOODPLAIN MANAGEMENT CRITERIA MANUAL <br /> <br />. <br /> <br />CHAPTER 4 <br />FLOODPLAIN <br />ADMINISTRATION <br />AND <br />DELINEATION <br />CCTION 1.0 <br />OODPLAIN <br />ANAGEMENT <br /> <br />1.6 <br /> <br />REGULATORYFLOODWAYS <br /> <br />The f100dway is defined as the channel plus any <br />adjacent floodplain areas, that must be kept free of <br />encroachment so that the 100-year discharge can be <br />conveyed with no more than one foot rise in the water <br />surface above the base flood elevations (BFE). <br />However, local communities may choose to adopt <br />stricter f100dway delineation criteria by allowing only 0.5 <br />foot or no rise above BFE. The f100dway represents the <br />community's regulatory limit of encroachment into the <br />100-year floodplain for those watercourses with the <br />established f100dway boundaries. <br /> <br />Local communities <br />may choose to <br />adopt stricter <br />floodway <br />delineation criteria <br />by allowing only <br />0.5 foot or no rise <br />above BFE. <br /> <br />Figure CH4-F101 is a conceptual representation of a channel section showing the <br />floodplain, flood fringe, and f100dway limits. Encroachment into the designated <br />f100dway is prohibited unless it has been demonstrated using appropriate detailed <br />engineering analyses that the proposed encroachment will not cause any rise in the <br />100-year water surface elevation. Since the f100dway is an extremely hazardous <br />area, construction of new building structures is not permitted. <br /> <br />Flood fringe is the area between the delineated <br />floodplain and f100dway boundaries. New <br />developments are allowed in the flood fringe in <br />accordance with the development guidelines <br />established in the floodplain management criteria. If <br />the regulatory f100dway has not been established, <br />new development in the floodplain is allowed only if it <br />can be demonstrated through appropriate detailed <br />engineering analyses that the proposed development <br />will not adversely impact surrounding properties. <br /> <br />1.7 UNDETERMINED OR APPROXIMATE <br />FLOODPLAIN <br /> <br />Numerous engineering studies have been performed <br />to develop the needed floodplain information <br />throughout the slate. However, many areas that are <br />subject to severe flooding have not yet been studied <br />and/or designated as a 100-year floodplain. Areas <br />outside of the designated floodplains can experience <br />substantial flooding during a storm event. These <br />known and/or undetermined flood hazard areas <br />should be studied in delailto determine flow rates and <br />the associated floodplain limits prior to the issuance <br />of a building or grading permit. <br /> <br />New developments within the identified 100-year <br />floodplain will be allowed in accordance with the <br />floodplain development guidelines oul/ined in this <br />section. If new developments are proposed to <br />encroach into or located adjacent to a previously <br />delineated approximate 100-year floodplain, the <br /> <br />AUGUST 2002 FLOODPLAIN <br />MANAGEMENT <br /> <br />Known and/or <br />undetermined flood <br />hazard areas should <br />be studied in detail <br />to determine flow <br />rates and the <br />associated floodplain <br />limits prior to the <br />issuance of a <br />building or grading <br />permit. If new <br />developments are <br />proposed to <br />encroach into or <br />located adjacent to a <br />previously delineated <br />approximate 100- <br />year floodplain, the <br />previously delineated <br />approximate <br />floodplain limits <br />should be restudied <br />by using the detailed <br />approach before the <br />developments can <br />occur. <br /> <br />CH4-106 <br />