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<br />E. Human Intervention and Operation. In general, evaluation oflevees shall not <br />consider human intervention (e.g. capping oflevees by sandbagging, earth fill, or <br />flashboards) for the purpose of increasing a levee's design level of protection during an <br />imminent flood. Human intervention shall only be considered for the operation of <br />closure structures (e.g. gates or stop logs) in a levee system designed to provide at least <br />100-year flood protection, including adequate freeboard as described above, provided <br />such operation is specifically included in the community's adopted emergency response <br />plan. <br /> <br />. <br /> <br />F. Analysis. For areas protected by a levee providing less than 100-yearprotection, flood <br />elevations shall be computed as if the levee did not exist. For the unprotected area <br />between the levee and the source of flooding, the elevations to be shown shall be <br />obtained from either the flood profile that would exist at the time levee overtopping <br />begins or the profile computed as if the levee did not exist, whichever is higher. <br />This procedure recognizes the increase in flood elevation in the unprotected area that is <br />caused by the levee itself. This procedure may_result in flood elevations being shown <br />as several feet higher on one side of the levee than on the other. Both profiles shall be <br />shown in the final report and labeled as "before levee overtopping" and "after levee <br />'overtopping" respectively. <br /> <br />Rule 10. StorIDwater Detention. <br />Hydrologic determinations and increased runoff from development and urbanization shall be <br />considered through detention measures to mitigate the higher runoff characteristics. <br /> <br />A. Stormwater/Floodwater Runoff Detention. The hydrologic analysis shall consider <br />the effects of on-site detention for rooftops, parking lots, highways, road fills, railroad <br />embankments, diversion dams, refuse embankments (e.g. solid waster disposal <br />facilities), rnill tailings, impoundments, siltation ponds, livestock water tanks, erosion <br />control dams, or other structures only ifthey have been designed and constructed with <br />the purpose of impounding water for flood detention and are owned, operated and <br />maintained by a govemment body. Detention structures that are randomly located, <br />privately owned, or privately maintained shall not be included in the hydrologic <br />analysis unless it can be shown that they exacerbated downstream peak discharges. <br /> <br />. <br /> <br />B. Irrigation Facilities. The CWCB recommends that irrigation facilities (e,g. ditches and <br />___ ____ n _ __ _ _ _ _ _canals) not be used as stormwater or pood..s:(JI1\,eyan~~J~ciliti~s, Ul1!e~s specifically <br />approved and designated by local governing jurisdictions and acknowledged by the <br />irrigation facility owners. The flood conveyance capacity of irrigation facilities shall be <br />acknowledged only by agreement between the facility owners and local governing <br />jurisdictions. The CWCB may designate and approve lOO-year floodplain information <br />for irrigation facilities if the above recommendations are met. <br /> <br />. <br /> <br />16 <br /> <br />DRAFT <br />