955
edits
Changes
Jump to navigation
Jump to search
Line 75:
Line 75: − + − + Line 86:
Line 86: − + Line 104:
Line 104: − +
→Time to drain the storage reservoir
:<math>d_{r}=a[e^{\left ( -bD \right )} -1]</math>
:<math>d_{r}=a[e^{\left ( -bD \right )} -1]</math>
Where
Where
:<math>a=\frac{Ar}{x}-\frac{i Ai}{x f'}</math>
:<math>a=\frac{A_{r}}{x}-\frac{i\times A_{i}}{x\times f'}</math>
and <br>
and <br>
:<math>b=\frac{xf'}{nAr}</math>
:<math>b=\frac{x\times f'}{n\times A_{r}}</math>
(The rearrangement to calculate the required footprint area of the facility for a given depth assuming three-dimensional drainage is not available at this time. Elegant submissions are invited.)<br>
(The rearrangement to calculate the required footprint area of the facility for a given depth assuming three-dimensional drainage is not available at this time. Elegant submissions are invited.)<br>
It is best applied to calculate the maximum duration of ponding on the surface of [[bioretention cells]], and upstream of the [[check dams]] of [[bioswales]] and [[enhanced grass swales]] to ensure all surface ponding drains within 48 hours.
It is best applied to calculate the maximum duration of ponding on the surface of [[bioretention cells]], and upstream of the [[check dams]] of [[bioswales]] and [[enhanced grass swales]] to ensure all surface ponding drains within 48 hours.
To calculate the time (''t'') to fully drain surface ponded water through the filter media or planting soil:
To calculate the time (''t'') to fully drain surface ponded water through the filter media or planting soil:
<math>t=\frac{dp'}{Kf}</math>
<math>t=\frac{d_{p}'}{K_{f}}</math>
Where <br>
Where <br>
d<sub>p</sub>' is the effective or mean surface ponding depth (mm).<br>
d<sub>p</sub>' is the effective or mean surface ponding depth (mm).<br>
<br>
<br>
To calculate the time (''t'') to fully drain the facility assuming three-dimensional drainage:
To calculate the time (''t'') to fully drain the facility assuming three-dimensional drainage:
<math>t=\frac{nAr}{f'x}ln\left [ \frac{\left (d+ \frac{Ar}{x} \right )}{\left(\frac{Ar}{x}\right)}\right]</math>
<math>t=\frac{n\times A_{r}}{f'\times x}ln\left [ \frac{\left (d_{r} \frac{A_{r}}{x} \right )}{\left(\frac{A_{r}}{x}\right)}\right]</math>
Where "ln" means natural logarithm of the term in square brackets <br>
Where "ln" means natural logarithm of the term in square brackets <br>
Adapted from CIRIA, The SUDS Manual C753 (2015).
Adapted from CIRIA, The SUDS Manual C753 (2015).