Laserfiche WebLink
<br />.> , <br /> <br /> <br />CHAPTER 2 <br />CWCS PRINCIPLES <br /> <br />SECTION 2 <br />CWCS PROPOSED <br />OPERATING <br />PRINCIPLES <br /> <br />COLORADO <br />FLOODPLAIN AND STORMWATER CRITERIA MANUAL <br /> <br />However, with urbanization of the upstream basins, the storm runoffs entering the <br />irrigation facilities have increased in rate, quantity, and frequency. Since the irrigation <br />facilities are not designed and constructed to safely convey storm runoff flows, they <br />should not be used as outfall points for urbanized area storm drainage systems, <br />unless it can be proven safe through appropriate detailed engineering analysis and <br />the facility owner's consent can be secured. Since the owner's liability from ditch <br />failure increases with the acceptance of storm runoff, the responsibility should be <br />clearly defined before a combined system is approved. <br /> <br />PROPOSED OPERATING PRINCIPLE <br /> <br />THE CWCB RECOMMENDS THAT IRRIGATION FACILITIES (I.E DITCHES AND <br />CANALS) NOT BE USED AS STORMWATER OR FLOOD CONVEYANCE <br />FACILITIES, UNLESS SPECIFICALLY APPROVED AND DESIGNATED BY <br />LOCAL GOVERNING JURISDICTIONS AND ACKNOWLEDGED BY THE <br />IRRIGATION FACILITY OWNERS. THE FLOOD CONVEYANCE CAPACITY OF <br />IRRIGATION FACILITIES SHOULD BE ACKNOWLEDGED ONLY BY <br />AGREEMENT BETWEEN THE FACILITY OWNERS AND LOCAL' GOVERNING <br />JURISDICTIONS. THE CWCB MAY DESIGNATE AND APPROVE 100-YEAR <br />FLOODPLAIN INFORMATION FOR IRRIGATION FACILITIES IF THE ABOVE <br />RECOMMENDATIONS ARE MET. <br /> <br />2.10 STORMWATER RUNOFF DETENTION <br /> <br />Detention basins have been commonly'used to mitigate increase in peak flows due <br />to new developments. Detention is also considered a viable method to reduce urban <br />drainage costs, Temporarily detaining storm runoff can reduce downstream flood <br />hazards as well as reduce pipe and channel sizes in urban areas. Storage also <br />provides for sediment and debris collection, which helps to maintain water quality in <br />downstream channels and streams. However, detention may not be necessary <br />where downstream drainage facilities in their original or previously improved <br />condition are adequate in capacity to carry flows from fully developed upstream <br />areas without negatively impacting downstream properties. <br /> <br />PROPOSED OPERATING PRINCIPLE <br /> <br />THE CWCB RECOMMENDS THAT LOCAL GOVERNMENT ENTITIES REQUIRE <br />ADEQUATE DETENTION FACILlTES BE APPROPRIATELY DESIGNED AND <br />CONSTRUCTED BY DEVELOPMENT PROPONENTS TO MITIGATE THE <br />INCREASE IN FLOWS CAUSED. BY URBANIZATION AND INCREASED <br />IMPERVIOUS SURFACES. THE FLOOD ATTENUATION BENEFITS OF <br />PUBLICALLY OWNED, OPERATED, AND MAINTAINED DETENTION FACILITIES <br />OR PUBLICALL Y CONTROLLED BUT PRIVATELY OWNED DETENTION <br />FACILITIES SHOULD BE FULLY RECOGNIZED FOR THE PURPOSE OF <br />DETERMINING FLOOD HAZARD AREAS DOWNSTREAM OF THE DETENTION <br />FACILITIES. THE ATTENUATION BENEFITS OF PRIVATELY OWNED <br />DETENTION FACILITIES THAT ARE NOT CONTROLLED BY PUBLIC AGENCIES <br />SHOULD NOT BE CONSIDERED IN FLOODPLAIN ANALYSES. <br /> <br />2.11 WATER RIGHTS <br /> <br />When drainage systems interfere with existing water rights, the value and use of the <br />water are affected. The existing drainageways and storage locations frequently <br />CWCS PROPOSED <br />OPERATING PRINCIPLES <br /> <br />MARCH 2004 - Draft <br /> <br />CH2-207 <br />