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<br />c?) <br /> <br />Worksheet 2: Time of concentration (Tc) or t~eI time (Tt) <br />Project jI1 AUL 17UJli1L- ~~ <br /> <br />TAcation <br /> <br />By_ <br /> <br />Checked <br /> <br />Date <br /> <br />Date <br /> <br />Circle one: Present C;;::el~ <br />Circle one: Tc ~hrOUgh subarea <br /> <br />NOTES: Space for as many as two segments per flow type can be used for each <br />worksheet. <br /> <br />Include a map, schematic, or description of flow segments. <br /> <br />Sheet flow (Applicable to Tc only) <br /> <br />Segment m <br /> <br />1. Surface description (Table 7.1-4).......... <br /> <br />2. Hanning's roughness coeff., Ii (Table 7.1-5) <br /> <br />3. Flow length, L (total L.i 300 ft) .......... <br /> <br />4. Two-yr 24-hr rainfall, P2 .................. <br /> <br />s. -Land slope. . .............................. <br /> <br />6. Tt. 0.og75(n~)~.8 <br />p. . <br />2 s <br /> <br />ftlft <br /> <br />Compute Tt <br /> <br />Shallow concentrated flow <br /> <br />Segment ID <br /> <br />7. Surface description (paved or unpaved) ..... <br /> <br />8. Flow length, L ............................. ft <br /> <br />9. Watercourse slope, s ....................... ftlft <br /> <br />10. Average velocity, V (Figure 7.1-4)......... <br /> <br />L <br />11. Tt .36OOV <br /> <br />Compute Tt ...... <br /> <br />Channel flow, <br /> <br />Segment 1D <br /> <br />12. Cross sectional flow area, a............... ft2 <br /> <br />13. Wetted perimeter, Pw ....................... ft <br /> <br />14. <br /> <br />a <br />r .- <br />Pw <br /> <br />Compute r ....... <br /> <br />Hydraulic radius, <br /> <br />15. Channel slope, 8 ............................ ft/ft <br /> <br />16. <br /> <br />Hanning's roughness coeff., n .............. <br /> <br />1 49 2/3 1/2 <br />V. . rn s ~ompute V....... <br /> <br />17. <br />18. <br />19. <br /> <br />Flow length, L ............................. ft <br /> <br />L <br />Tt .36OOV <br /> <br />Compute Tt <br /> <br />Watershed or subarea Tc or Tt (add Tt in steps 6, II, and 19) ..~.... <br /> <br />20. <br /> <br />ftls <br /> <br />ft <br /> <br /> <br />in <br /> <br />hr <br /> <br />hr <br /> <br />.lo.Ol ~ I <br /> <br />ft <br /> <br />ftls <br /> <br />hr <br /> <br />1+1 <br /> <br />h: lo.o'i J <br /> <br />7.1- 32 <br /> <br />10/89 <br />