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<br />- <br /> <br />. <br /> <br />, , <br /> <br />Worksheet 3: Time of concentration (Tcl or travel time (Tt) <br /> <br />Project <br /> <br />By_ <br /> <br />-CJ <br /> <br />. 7. Surface description (paved or unpaved) ..... <br />S. F'ow length, L ............................. ft <br /> 9. Watercourse elope, . ....................... ft/ft <br /> 10. AverAge velocity, V (figure 3-1) ........... ft/. <br /> 11. L Compute Tt hr 1+1 -CJ <br /> Tt - 360iiV ...... <br /> <br />I <br />f <br />i ( <br />it <br />it- ___ <br />l <br /> <br />Date <br /> <br />Location <br /> <br />Checked <br /> <br />Date <br /> <br />Circle one: Present Developed <br />Circle one: Tc Tt through Bubarea <br /> <br />NOTES: SpAce for .a many as two segments per flow ty~ can be used for each <br />worksheet. <br /> <br />Include 8 map, 8chematlc, or descrlptlon of flow le8mentl. <br /> <br />Sheet flow (Applicable to Tc only) <br /> <br />SegllOnt ID <br /> <br />1. Surface description (table 3-1) ............ <br /> <br />2. Hanning'. roughne.. coeff., n (table 3-1) .. <br /> <br />, <br /> <br />3. Flow length, L (total L,i 300 ft) .......... ft <br /> <br />4. Two-yr 24-hr rainfall, P2 .................. 1n <br /> <br />5. <br /> <br />ft/tt <br /> <br />Land <br /> <br />alope, I .............................. <br />0.007 (nL)O.g <br />P 0.5 0.4 <br />2 · <br /> <br />hr <br /> <br />1+1 <br /> <br />6. <br /> <br />Compute Tt ...... <br /> <br />T - <br />t <br /> <br />Shallow concentr3ted flow <br /> <br />Segment ID <br /> <br />Channel flow <br /> <br />Seg_nt ID <br /> <br />.12. Croat aectIonal flow area, a............... ftZ <br /> <br />13. Wetted peri.eter, Pv ....................... ft <br /> <br />14. <br /> <br />. <br />r -- <br />Pw <br /> <br />Compute r ....... <br /> <br />ft <br /> <br />Hydraulic radius, <br /> <br />15. Channel slope, I ........................... ftlft <br /> <br />16. <br /> <br />Hannlns'a roughnesl coeff., n .............. <br />I 49 2/3 1/2 <br />V. . r s Compute V....... <br />D <br /> <br />ft/. <br /> <br />17. <br /> <br />18. <br /> <br />Flow length, L ............................. ft <br /> <br />19. <br /> <br />L <br />Tt - 3600 V <br /> <br />1+/ <br /> <br />COllpute Tt <br /> <br />hr <br /> <br />20. <br /> <br />Watershed or subarea Tc or Tt (add Tt in steps 6, 11, and 19) ..~.... <br /> <br />(210- VI.TR.55, Second Ed., June 1986) <br /> <br />-a <br /> <br />hr <br /> <br />l <br /> <br />E <br /> <br />7 <br /> <br />e <br /> <br />9 <br /> <br />D~ <br /> <br />D-3 <br /> <br />- <br />