Page 6 - Water Pollution Management - Management Plans - Understanding your Risk
P. 6

Run off estimation small catchments







         CIRIA Method Less than 50 Ha



         •    Step 1 Establish site annual average rainfall.





         •    Step 2 Calculate catchment area (ha)





         •    Step 3 Determine soil type






         •    Step 4  Read unit runoff from table (litres per second per hectare)





         •    Step 5 Select Return Period





         •    Step 6 Peak flow (l/s) = Catchment area (ha) x Runoff Factor x Return Period Factor









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