Laserfiche WebLink
2x S <br />f r- ~ ~o °~ ACS T.P-~S <br />3-2 1 <br />~~ ~~ <br />then computed by dividing the total overland flow length by the average <br />velocity. <br />• <br />., : s s 1 <br />so <br />so <br />xo <br />xo <br />9 s <br />S <br />'" s <br />z <br />t <br />z s s <br />t <br />s s <br />.1 .x .s .s x z s s so zo <br />' vELOC ITY iq FEET PER SECONp <br />Figure 3-1.--Average velocities for estimating travel time for <br />overland flow. <br />I <br />Storm sewer or road gutter flow <br />Travel time through the storm sewer or road gutter system to the main <br />open channel is the sum of travel times in each individual component of <br />the system between the uppermost inlet and the outlet. In most cases <br />average velocities can be used without a significant loss of accuracy. <br />During major storm events, the sewer system may be fully taxed and ad- <br />ditional overland flow may occur, generally at a significantly lower <br />velocity than the flow in the storm sewers. By using average conduit <br />sizes and an average slope (excluding az~y vertical drops in the system), <br />the average velocity can be estimated using tvlanning's formula. <br />Since the hydraulic radius of a pipe flowing half full is the same as <br />when flowing full, the respective velocities are equal. Travel time may <br />to xo <br />sa <br />m <br />to <br />s <br /> <br /> <br /> <br /> <br />i <br /> <br />t, <br />r <br />r <br />