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d9ov /99d Serttra 1l Afixe" Poll-~lliniig Draiiiy;r Contra/ • 3 <br />StUtln Duration <br />rl storm duration oE2~ hours .vas used to model the watershed for the Seneca II Kline azra. <br />Return Period/Preci tp'tation <br />r1 preopitation amount is required for the appropriate return period The following precipitation amounts <br />were used for Seneca II 1\[itre area: <br />10-tear, 24hour event 1.7 inches <br />100-}~eaz, 24-hour evrnt 25 inches <br />The predpitation amounts were obtained from the Seneca II Dlirte Permit application. <br />Hvdronr~Tnh ResRes~onse Shane <br />~1 unit h}'dcograph is chosen Eor each drainage uea oc sub-azea model to predict the tun-ofE cesponse. The <br />• h}'drograph responses available in the SEDC~ID+ model aze slow, mediurt>, and fast. .~ slow response <br />corresponds to a foaested arra or an area with a number of obstructions. ~1 fast response corresponds [o an <br />umegetated or poodt• protected azea. Fast arrd medium h}~drograph responses were chosen for disnrrbed and <br />undisturbed azeas, respectne]}'~ <br />The internal convolution increment is 0.05 hours and values aze saved a[ the user specified internal of 0.1 <br />hours or greater. A convolution increment of 0.1 was specified for the Seneca II Tt[ine Area. <br />Drainage Basin Area <br />The drainage azeas wece detemtated by direct measurement from a 1" = 500' map, with a contour internal <br />of 10 feet The watershed azeas aze shown on Exhibit 7-19. <br />Time of Concentration. T. <br />The time of concentration was calnilated using the SCS upland method (a urilin' of SEDCAD+). All <br />• hcdraulic lengths, drainage heights and slopes were measured direcdv from a I" = 500' map, with a contour <br />inten~al of ]0 feet The calculated values for each structure aze shown on the SF.DC.r1D+ printouts. <br />7-12-3 Revised 05/08/96 <br />