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<br /> <br />1 <br />Worksheet 3: Time of concentration (Tc) or travel time (Tt) <br />Project: CASTLE ROCK QUARRIES <br />Location: Douglas County, Colorado <br />Condition: Post mining <br />Calculations for: Tc <br />NOTES: <br />Shee[ Flow (Applicable to Tc only) Segment <br />1. Surface description (table 3-1) ......................................... <br />2. Manning's roughness coeff., n (table 31) ........................ <br />3. Flow length, L (total L ~= 300 ft.) ..................................... <br />4. Two-yr 24-hr rainfall, P2 ................................................... <br />5. Land slope, s ................................................................... <br />6. Tt=[0.007 (nL)"(0.6)]/[P2"(0.5) s"(0.4)] Compute Tt........ <br /> Sha llow concentrated Flow <br /> 7. Surface description (paved or unpavetl) .......................... <br /> 6. Flow length, L .................................................................. <br /> 9. Watercourse slope, s ....................................................... <br /> 10. Average velocity, V (figure 3-1) ....................................... <br /> 11. Tt = U(3600 V) Compute Tt......... <br />Shallow concentrated flow (continued) <br />7. Surface tlescriplion (paved or unpavetl) .......................... <br />6. Flow length, L .................................................................. <br />9. Waterwurse slope. s ...................................................... <br />10. Average velocity, V (figure 3-1) ....................................... <br />11. Tt = U(3600 V) Compute Tt........ <br />Segment lD <br />fl <br />ft/fl <br />tVs <br />ht <br />By: TPY Date: <br />Checked: JGJ Date: <br />BASIN J <br />7/21 /95 <br />7/21 /95 <br />0.3 I <br />T2 T3 <br />unpaved unpaved <br />409 1,084 <br />0.0611 0.0507 <br />3.99 3.63 <br />0.026 0.083 0.11 <br />Segment ID <br />fl <br />ft/ft <br />tVs <br />hr <br /> <br /> Channel Flow Segment <br /> 12. <br />13. Cross sectional flow area, a ............................................. I <br />Wetted perimeter, Pw ....................................................... <br /> 14. Hydraulic radius, r =a/pw Compute r........... <br /> 15. Channel slope, s .............................................................. <br />' 16. <br />17. Manning's roughness coeff., n ......................................... <br />V = (1.49 r^(2/3', s"(112))/n Compute V............ <br /> 16. Flow length. L .................................................................. <br /> 19. Tl = U(3600 V) Compute Tt........... <br />20. Watershed or subarea Tc or Tt (add Tt in steps 6, 11, and 19) ............................................ <br />(210-V 1-TR-55, Second Ed., June 1986) <br />1 <br /> <br />...... hr 0.42 <br /> <br />