Infiltration practice for control of urban stormwater

Infiltrating stormwater locally into the ground instead of discharging to conventional pipe sewers is increasingly considered as a means of controlling urban stormwater runoff. This paper reviews the most recent developments within this field and points out some of the major problems remaining. Easy-to-use methods for designing stormwater infiltration structures are available but methodologies for determining the design parameters based on local conditions and technologies for clogging prevention are needed. No evidence so far points at a high risk of groundwater contamination but the quality of surface soils will decrease due to long-term infiltration of polluted stormwater runoff. Simplistic modelling approaches based on conceptual process descriptions are needed for assessing the impact on soil and groundwater in local areas. The perspectives in relation to control of stormwater runoff are clear; the runoff peaks and volumes are decreased, and the urban hydrological cycle is returned to a more natural state. In some aspects stormwater infiltration is more effective for runoff reduction and abatement of pollution discharges than detention basins. In the future, measures to promote urban stormwater infiltration need to be developed.