ACO
Catchment Hydraulics
About Us ACO Group of Companies
Local Sales Support
Home         
      1300 765 226 (AUS)   0800 448 080 (NZ)   + 61 2 4747 4000 (Export)   Contact ACO Online   


Catchment Hydraulics - calculating run-off

To calculate the correct size of trench drain, catchment run-off must be calculated.

Catchment area - length x
width of pavement
x
Rainfall intensity in mm per hour  
Run-off coefficient - ie. pavement
material, some surfaces absorb
liquids e.g. block pavers
 
 
Refer to 'Australian Rainfall and Run-off' or AS/NZS 3500.3 - 'Plumbing and Drainage Code' for rainfall intensities.
 
Other factors that affect the transfer of liquids include:
Ground fall along trench %
Position and size of outlet pipe
Surface roughness of trench material. Manning's coefficient of roughness
Pavement angle of approach to trench - this can affect grate hydraulics (steep slopes may cause bypass)

Determining trench size

The calculated run-off , is combined with the other factors above to determine the correct size of trench. The trench size is specified by the clear opening and invert depth - changing either or both of these will create a smaller or larger ‘flow area’.
Clear opening of trench is the normal specified dimension, e.g., 100mm, 200mm, etc.
Overall grate and outside trench dimensions are misleading.

 

| Home | About Us | Local Sales Support | Contact |

© ACO AUSTRALIA 2007