(A) Persons shall conduct land-disturbing activity so that the post construction velocity of the ten-year storm runoff in the receiving watercourse to the discharge point does not exceed the greater of:
(1) The velocity established by the Maximum Permissible Velocities Table set out within this section; or
(2) The velocity of the ten-year storm runoff in the receiving watercourse prior to development.
(B) If condition of division (A)(1) or (A)(2) of this section cannot be met, then the receiving watercourse to and including the discharge point shall be designed and constructed to withstand the expected velocity anywhere the velocity exceeds the "prior to development" velocity by 10%.
(C) Table 1 - Maximum Permissible Velocities**:
Material | F.P.S. (feet per second) | M.P.S. (meters per second) |
Material | F.P.S. (feet per second) | M.P.S. (meters per second) |
Fine sand (noncolloidal) | 2.5 | 0.8 |
Sandy loam (noncolloidal) | 2.5 | 0.8 |
Silt loam (noncolloidal) | 3.0 | 0.9 |
Ordinary firm loam | 3.5 | 1.1 |
Fine gravel | 5.0 | 1.5 |
Stiff clay (very colloidal) | 5.0 | 1.5 |
Graded, loam to cobbles (noncolloidal) | 5.0 | 1.5 |
Graded, silt to cobbles (colloidal) | 5.5 | 1.7 |
Alluvial silts (noncolloidal) | 3.5 | 1.1 |
Alluvial silts (colloidal) | 5.0 | 1.5 |
Coarse gravel (noncolloidal) | 6.0 | 1.8 |
Cobbles and shingles | 5.5 | 1.7 |
Shales and hard pans | 6.0 | 1.8 |
** Source - Adapted from recommendations by Special Committee on Irrigation Research, American Society of Civil Engineers, 1926, for channels with straight alignment. For sinuous channels, multiply allowable velocity by 0.95 for slightly sinuous, by 0.9 for moderately sinuous channels, and by 0.8 for highly sinuous channels. | ||
(Ord. 2020-09-07, passed 9-21-20)