Agenda Reports Pack (Public) 15/10/2012, 19.00 - Meetings ...

equired. The aim of all development should be to achieve 50% attenuation of theundeveloped sites surface water run-off at peak times and where possible achieve100% attenuation. 5 ”2.5. In addition to this any new development in the borough must adhere to PlanningPolicy Statement 25 (PPS25). PPS25 states that, following the application of thesequential test (this test is essentially a means of avoidance planning; developmentshould be directed to areas with the least risk of flooding), if there is no suitable landin lower risk zones, development may go ahead in exceptional cases; the so-called‘exception test’. However, in applying this test the Council must demonstrate thatother sustainability criteria outweigh the flood risk, that the risk can be mitigated andthat the site is safe.2.6. The Task Group welcomed the measures the Government and the Council had putin place to mitigate the risk of surface water flooding in new developments. Howeverthe Task Group felt that the Council, and other relevant parties such as theEnvironment Agency and Thames Water, could do more to encourage newdevelopments to adopt SUDs. The Task Group considered what SUDs it felt wouldbe most appropriate for each level of development individual property level,community level and a strategic level, and has detailed its findings andrecommendations below.SUDs: Individual Property Level2.7. Urban creep refers to the cumulative impact that paving over front and rear gardensis having, not only in Hammersmith and Fulham, but across London and other townsand cities. This can have a significant impact on the natural drainage of surfacewater, as water that previously soaked into the ground has nowhere to go and canincrease the risk of surface water flooding. Home improvements, such as sidereturns or conservatories, can also increase demands on surface water drainagesystems.2.8. Householders are no longer permitted to lay impermeable surfaces in front gardensgreater than 5 square metres without planning permission. However residents arestill permitted to lay impermeable surfaces in their back gardens. It makes sense toretain as much natural drainage as possible in the borough. The Task Group cameto the conclusion that, should the Council identify areas in the borough that are atparticular risk of surface water flooding, the Council should encourage applicants toincorporate SUDs to mitigate the impact their development would have on surfacewater flooding. Residents should be encouraged to undertake a flood riskassessment.2.9. The Task Group noted that many residents in the borough had, in the past, appliedfor side or rear extensions to their properties. In addition a significant number of localresidents had also applied for basement extensions. The Task Group took the viewthat it was highly likely that this trend would continue over the coming years. TheTask Group noted the advice from the Environment Agency that it was important notto overlook the cumulative impact that smaller improvements to properties across an5 Ibid.- 18 -Page 177