| The designer must fully assess the storm characteristics of
the location of his site and derive a suitable depth of rainfall
for the period of the storm's duration. Generally, M5-60 storms
are chosen and are seen as a reasonably practicable return period
to use.
Design rainfall should be expressed in metres for the soakaway
calculation. In areas where flooding is likely or there is
no facility for an overflow in the event of an unusually heavy
storm, the designer should consider increasing the Factor
of Safety in Design Options.
New to Version 4 is the Z1, Z2 factor calculation.
This feature has been added to reflect the methodology adopted
in BRE 365 and is used to derive a statistical probability
of rainfall depths for various locations in the UK.
The form below shows how it works.
Simply select the Z1 factor from your rainfall duration and
ratio r...
Then from the Z2 tab select the M10 Growth Factor Z2 for
your M5 rainfall depth and location in the UK.
|
Visual Soakaway Design - Help