APPENDIX A: TIME OF CONCENTRATION (T C) WORKSHEET

Project:_______________________________ By:_____________ Date: ______________

Location:______________________________ Checked_________ Date: ______________

Circle one:PresentDeveloped ________________________________________

Circle one:TCTC through subarea _______________________________

NOTES:   Splice for as many as two segments per flow type can be used for each worksheet.

      Include a map, schematic, or description of flow segments.

 

Sheet Flow (Applicable to TC only)Segment ID
1. Surface description (App. B, Table 8)
2. Manning's roughness coeff., “n” (App. B, T.8)
3. Flow length, L (total L 300 feet)ft.
4. Two-year, 24-hour rainfall, P2in.
5. Land slope, sft./ft.
6. Tt = {0.007 (nL) 0.8}/{P20.5 s0.4} Compute Tt..hr.

 

Shallow Concentrated Flow Segment ID
7. Surface description (paved or unpaved)
8. Flow length, Lft.
9. Watercourse slope, sft./ft.
10. Average velocity, V (App. B, Table 8)ft./s
11. Tt=L/(3600V)Compute Tthr.

 

Channel FlowSegment ID
12. Cross sectional flow area, aft.2
13. Wetted perimeter, pw ft.
14. Hydraulic radius, r=a/pw Compute rft.
15. Channel slope, sft./ft.
16. Manning's roughness coeff., “n”
17. V=(1.49 r2/3 s1/2)/nCompute Vft./s
18. Flow length, Lft.
19. Tt=L/(3600V)Compute Tthr.
20. Watershed or subarea Tc or Tt (add Tt, steps 6, 11, 19)hr.