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<br />&:J <br /> <br />Worksheet.2: Time of concentration (Tc) or travel time (Tt) <br /> <br />Project i./tAVtL 11'LVU<:. ~j <br /> <br />BY~ <br /> <br />Date <br /> <br />Location <br /> <br />Checked <br /> <br />Date <br /> <br />Circle one: @~ Developed <br /> <br />Circle one: Tc Tt through subarea <br /> <br />NOTES: Space for as IUny as two seglllents per flow type can be used for each <br />workaheet. <br /> <br />Include a IUp, schelUtic, or description of flow segments. <br /> <br />2. Manning's roughness coeff., 11 (Table 7.1-5) <br />3. Flow length, L (total L.i300 ft) .......... <br /> <br />ft <br /> <br /> <br />\'AVe"Q <br />0.0 \ <br />ZSo <br />L.( <br /> <br />Sheet flow (Applicable to Tc only) <br /> <br />Seplent m <br /> <br />1. Surface description (Table 7.1-4).......... <br /> <br />4. Two-yr 24-br rainfall, P2 .................. <br /> <br />in <br /> <br />s. Land slope, a.............................. <br /> <br />6. Tt _ 0.007s(n~)~.8 <br />P O. . <br />2 s <br /> <br />ft/ft <br /> <br />Compute Tt <br /> <br />hr <br /> <br />- p. 06'\-1 <br /> <br />Shallow concentrated flow Segment ID <br /> <br />7. Surface description (paved or unpaved) ..... <br />8. Flow length, L ............................. ft <br />9. Watercourse slope, . ....................... ft/ft <br />10. Average velocity, V (Figure 7 . 1-4 ). . . . . . . . . ft/s <br />11. L Compute Tt hr -10' 02-( I <br />T t . "3'6'OO'V ...... <br /> <br />Channel flow Sepent m <br /> <br />12. Cross sectional flow area, a............... ft2 <br /> <br />13. Wetted perimeter, Pw ....................... ft <br /> <br />14. <br /> <br />Hydraulic radius, <br /> <br />a <br />r .- <br />Pw <br /> <br />Colllpute r ....... <br /> <br />ft <br /> <br />15. Channel slope, s ........................... ft/ft <br />16. Hanning's roughness coeff., n .............. <br />17. V . 1.49 r2/3 sl/2 Compute V ft/s <br /> ....... <br /> n <br />18. Flow length, L ....... ................ ...... ft <br />19. L Compute Tt hr 1+1 <br />T t - 36'OOV <br /> <br />20. Watershed or subarea Tc or Tt (add Tt in steps 6, II, and 19) ..~.... <br /> <br />h:~ <br /> <br />7.1-32 <br /> <br />10/89 <br />