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<br /> <br />Flood Control <br /> <br /> 1000 <br /> 900 <br /> BOO <br /> 700 <br />tJ) <br />II: <br /><l <br />...J 600 <br />...J <br />0 <br />0 <br />"- 500 <br />0 <br />Vl <br />Z <br />0400 <br />...J <br />...J <br />:; 300 <br /> 200 <br /> 100 <br /> 0 <br /> <br /> . <br /> . <br /> . <br /> . <br /> . <br /> . <br />PACIFIC SOUTHWEST: <br /> . <br /> . <br /> . <br /> . <br /> . <br /> . <br /> . <br /> . <br /> . <br /> . I <br /> . <br /> : / <br /> .. I <br /> . <br /> . <br /> . <br /> . I <br /> . <br /> . CALIFORNIA <br /> . <br /> . <br /> . / // <br /> . <br />. <br />. / / LOWER <br />. <br />/'" / COLOR tOO <br />"..,' ~GI'lEAT IASIN <br />. (.UP,)~R ~~ORAoO <br /> . ._ _e <br /> <br />1965 1980 2000 2020 <br /> <br />Figure 21.-FUture average annual flood damage <br />(with 1965 flood control measures). <br /> <br />(dams, levees, channel improvements), (2) by institu- <br />ting nonstructural measures in flood.prone areas to <br />reduce damage (parks, flood plain zoning, flood <br /> <br />forecasting and warning programs), and (3) land <br />management and treatment programs in upstream <br />areas. <br />Controlling flood damages in urban areas often is <br />compatible with other modern urban needs, such as <br />the need for more recreation land and open space. <br />Parks, playgrounds, nature reserves, and golf courses <br />can endure floods with a low degree of property <br />damage and little or no danger of loss of life. This <br />kind of flood plain use, or other flood plain <br />management measures, could be applied to about 525 <br />miles of streams in or adjacent to urban communities <br />in California. <br />Favorable tax adjustments for private land <br />dedicated to agriculture, conservation, recreation, or <br />other low.density use can be an effective means of <br />preserving flood plain lands in an underdeveloped <br />state, thus reducing damage. Except in the State of <br />California, where the Williamson Act provides for this <br />approach, there is only limited application In the <br />Pacific Southwest for this course of action. <br />The present systems for collection of operational <br />hydrometeorological data for forecasting floods are <br />inadequate in many parts of the Pacific Southwest. <br />The flood warning systems for many areas are <br />nonexistent and for those places where a flood <br />warning system is in being, sufficient time quite often <br />is not available for evacuation of people and contents <br />of buildings from flood plains, and the construction <br />of emergency measures for protection of property. <br /> <br />Plan ResponS8 <br /> <br />The base plan for flood control includes flood <br />forecasting, flood control reservoirs, floodwater reo <br />tardation structures, levees and channels, flood plain <br />zoning, and watershed treatment. <br />Stomge. - Except for small reservoirs in the up' <br />stream watershed areas, reservoirs for flood control <br />alone generally are not economically feasible in the <br />Pacific Southwest. Therefore, almost all reservoirs <br /> <br /> Table S.-Projected flood control storage requirements <br /> Existing Additional Requirements <br />Region ...illL 1965-1980 1981.2000 2001-2020 1965,2020 <br /> (Thousands of acre-feet) <br />California 5,915 4,564 5,458 1,995 12,017 <br />Great Basin 322 578 580 186 1,344 <br />Lower Colorado 10,701 3,145 596 648 4,389 <br />Upper Colorado ~ ~ 500 60 2,300 <br />Pacific Southwest 18,158 10,027 7,134 2,889 20,050 <br /> <br />60 <br />