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Storm Drainage

Storm Sewers

Storm sewers are providing the minor system conveyance for the app. 2 year London storm event and constructed underground, usually under roads and in parking lots, which aids in preventing flooding by draining rainwater away from buildings and road surfaces. The storm drainage also provides the major flow conveyance for storm events larger than the 2 year up to the 250 year (regional) storm events. These storm flows to a stream, tributaries, water courses or river such as the Thames River. Most of the newer storm sewers built today are connected to Stormwater Management Facilities. The Stormwater Management Facilities typically capture the minor and major storm flows and removes sediment prior to discharging back into the environment such as streams and rivers.


Did you know that London has:

1,322 kilometres of storm gravity sewers;

18,472 storm access holes;

100 Stormwater Management (SWM) facilities; and

28,897 catchbasins