Page 10 - Merton SuDS Design and Evaluation Guide
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2.2 The ground becomes saturated
Overview After a while the surface of the landscape Where the ground is permeable, water Where the ground is impermeable, Overview
begins to soak into lower soil profiles and
water begins to trickle and flow across
can absorb no more water.
the surface, collects in natural
then the underlying geology. This is called
infiltration and is common on sandy, gravelly
and limestone soils. depressions, and is stored in wetlands.
These natural features attenuate the rate
and volume of flow of rainwater running
off the landscape. These flows are called
natural or greenfield runoff.
In landscapes with infiltrating soils, after Surface flow rates are small at first, but increase
interception losses have taken place, most with higher intensity rainfall events. The
rainwater is lost by soaking into the ground. volume of runoff will generally be greater with
increased rainfall intensity and duration.
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London Borough of Merton SuDS D & E Guide © 2018 McCloy Consulting & Robert Bray Associates London Borough of Merton SuDS D & E Guide © 2018 McCloy Consulting & Robert Bray Associates
