WSP06650 - Laserfiche WebLink

Home Browse Search

0014 J'~ 3 The flood data used to define the high-flow storage requirements may be analysed and presented in several ways. At a gaging station, the greatest known historic flood or the greatest flood experienced during the period of operation could be used; however this procedure would not define how fre- quently such an event might be expected in the future. At a gaging station, the distribution of flood events could be used, but this does not allow for the differences between stations. A generalized distribution of flood events in a long-term common period based on data from all sites could be used; but this method, although appropriate in some parts of the United States, was found to show excessive variations throughout Kansas. The expectancy of storage requirements needed would be best defined if records were avail- able over a long-term period at all sites. Because long records are avail- able at relatively few sites, regression techniques have been used in this re- port to extend short-term streamflow records to a 40-year period, 1921-60. Also historic flood discharges, where available, were used to modify the fre- quency curves drawn from the 40-year records and to indicate the shape of the frequency curve at sites where historic flood data are not available. Through the use of flood discharge frequency curves developed at 101 gaging stations in Kansas and vicinity, this report presents for selected chances of recurrence the storage capacity necessary to store and release gross flood volumes at various rates. Also the storage capacity for the 101 sites is shown for the maximum flood volume of record. Investigators of flood control measures may wish to evaluate various operational plans for releasing flood runoff from storage. To aid their study, the design outflow release rates in this report are considered a constant with excess inflow retained as storage. The outflow rate in this report is a gross amount with no allowance for evaporation and seepage losses, which need to be evaluated separately for each specific reservoir site. Frequently streamflow data are needed at sites where no gaging-station records have been obtained. Procedures for estima ting high-flow storage requirements at ungaged sites are outlined and illustrated. The order of presentation in this report is: first to describe the develop- ment of frequency curves of flood runoffof various durations; second, to de- velop and present data on flood-volume storage requirements at gaging sta- tion sites; third, to explain the variations in the storage-outflow relations so as to provide a means of estima ting storage requirements at sites where specific streamflow information is not available.