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An econanic cost analysis for each drainage basin is made to determine the unit drainage fee as part of the drainage basin study. THE CITY/COUNTY DRAINAGE POLICY REQUIRES THAT DEVELOPERS PAY FOR THEIR STORM WATER DRAINAGE IMPROVEMENTS. WHERE PUBLIC IMPROVEMENTS ARE NECESSARY AND JUSTIFIED, GENERALLY IN CONFORMANCE WITH A DRAINAGE BASIN STUDY, FUNDING MECHANISMS WILL BE DEVELOPED ON A CASE-BY-CASE BASIS AND IN GENERAL CONFORMANCE WITH LOCAL POLICY, ORDINANCES, RESOLUTIONS AND/OR REGULATIONS. 1.4 Development Near Channels, Irrigation Ditches and Drainageways 1.4.1 Drainage and Development Near Irrigation Ditches Irri gation canals often capture storm water from upstream areas. Urban development tends not only to increase the volume and the flow rate of storm runoff, but also to decrease the time required for runoff to reach a peak rate. In addition, the concentration patterns of runoff may be changed. The net effect of urbanization is usually an increase in peak flow rate received downstream. ~ Changing historical routing patterns into irrigation canals could create severe 1 i abil ity problems. However, the use of i rri gati on canals for storm water conveyance generally is not acceptable since the capacity of canals decreases downstream, and the slopes, which tend to be small, 1 es sen the stormwater transport capabil iti es. Since ditch owners can be held liable in case of ditch failure during intense storm events, acceptance of increased runoff may aggrevate problems for ditch systems. Occasionally, however, the only alternative is to direct runoff into existing ditches. Wherever new deve 1 opment wi 11 alter patterns of drai nage into irri gat ion ditches by increasing flow rates or volumes, or will change the historic concentration points of runoff, each new development shall obtain written consent from canal owners. The discharge of runoff into irrigation ditches shall be approved only if such discharge is consistent with the appropriate master plan. Problems with drainage into canals often can be avoided if storm runoff is directed into natural and historic drainageways, and the irrigation canals are not used. Runoff from new urban deve 1 opment shall be directed into hi stori c and natural drainageways, avoiding discharge into canals, except as required by water rights or where no reasonable alternative exists. Canals often intercept natural drainageways that are part of the major drainage system. Irrigation facilities may, however, suffer considerable damage in the event of a major storm, which might cause flood damage due to failure of the canal at some undetermined point downstream. 1-9 I I I I I I I I I I I I I I I I I I I