+))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))),
*
*
*Example Calculation:
*
*
*
*
*
Annual soil loss in watershed = 0.9 acre-feet/year
*
*
(from Universal Soil Loss Equation or
*
*
other method, i.e. design charts)
*
*
*
*
Desired pond efficiency = 70% or 0.63 acre-feet of sediment
*
*
trapped each year.
*
*
*
*
Annual volume of runoff from watershed draining into
*
*
proposed pond = 400 acre-feet/yr.
*
*
*
*
For 70% efficiency using median curve C/I = 0.032
*
*
Required pond capacity C = 0.032 x 400 = 12.8 acre-feet.
*
*
*
*
Assuming average depth of pond of 6 ft, required pond
*
*
area about 2.1 acres. Pond should be cleaned when
*
*
capacity reduced 50%.
*
*
*
*
(Note: Trap efficiency decreases as volume of pond
*
*
decreases; this has not been considered in the example.)
*
*
*
*
Volume available for sediment = 50% x 12.8 = 6.4 acre-feet.
*
*
*
*
Years between cleaning =
6.4
*
)))) [approximately] 10 years.
*
*
*
0.63
.)))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))-
FIGURE 13 (continued)
Capacity of Sediment Control Ponds
7.1-303
Previous Page
