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<br />average annual damage with and without the improvement in order to deter- <br />mine project feasibility. In the case of extensive channel improvements <br />that might serve to accelerate flows in a significant portion of a river <br />system, the accelerating effect must be simulated for a large range of <br />flood magnitudes in order to determine the extent to which flow magnitudes <br />downstream are augmented. <br />In the case of levee protection. the frequency and severity of sudden <br />floOding from levee failures and the increased flooding of lands immedi- <br />ately upstream of a levee system tnust be evaluated. and the consequences <br />must be compared with the reduced flOOding due to levee protection <br />against floods of design magnitude and smaller. As in the case of exten- <br />sive channel improvements. the accelerating effects of extensive levee <br />itnprovements can be substantial and should be evaluated for a large <br />range of flood magnitudes. <br />In the case of reservoir projects. it is usually necessary to simu- <br />late the effects of each reservoir on downstream flows for all relevant <br />magnitudes of peaks and volumes of inflows. Here it is particularly <br />important that each hypothetical flood has a peak flow and volumes for <br />all pertinent durations that are commensurate in severity, so that each <br />computed regulated flow will have a probability or frequency that is <br />comparable to that of the corresponding unregulated flow. This balance <br />between peak flow and volumes is of special importance when studies are <br />made to select alternative reservoir or channel improvement projects. <br />lfuere a number of reservoirs operate in a system or where one or more <br />reservoirs affect damages at remote downstream locations. it is important <br />that a proper balance is attained among inflows to the various reservoirs <br />and with runoff downstream of the reservoirs so that regulatory effects <br />can be accurately evaluated and so that the correct weight will be <br />assigned to each reservoir when determining its proportional effect in <br />reducing downstream flooding. <br /> <br />1-03 <br />