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

Act of 2010 (FWMA). Under the FWMA all London boroughs were designated LeadLocal Flood Authorities. As a Lead Local Flood Authority Hammersmith and FulhamCouncil has the responsibility to manage local flood risk, which is defined as floodrisk originating from surface runoff, groundwater and ordinary watercourses; tidalflood risk from the River Thames is not the responsibility of the Council but of theEnvironment Agency (EA).The FWMA 2010 and the FRR 2009 placed new statutory duties on the Councilwhich include:► managing flood risk in a co-ordinated way and creating effective partnerships withadjacent Local Lead Flood Authorities and other key stakeholders such as ThamesWater, the Environment Agency and Transport for London (TfL);► investigating flood events in the borough;► developing and managing a public register of Flood Risk Management Assets;► approving, maintaining and adopting sustainable drainage systems,► the production of a number of documents which include:o Preliminary Flood Risk Assessment (PFRA);o flood risk and flood hazard maps;o a Local Flood Risk Management Strategy,o a Local Flood Risk Management Plan.Over 60% of the area of the borough and about 75% of the population is potentiallyat risk of tidal flooding from the River Thames. Whilst the likelihood of tidal flooding islow due to London’s flood defences, were it to occur, the consequences would bevery severe. In addition to tidal flooding much of the borough is at risk of surfacewater flooding, including sewers surcharging to unprotected basement properties.Climate change, including more frequent extreme weather events and an increase inimpermeable areas, are expected to increase the frequency and severity of this typeof flooding. Thames Water records show that almost 700 properties have beenflooded from sewer flooding events over the last 10 years; all of which wereassociated with heavy rainfall. Most of these have been basement properties. TheTask Group is of the view that, in reality, significantly more properties have beenaffected over the last 10 years but many of those people affected have not reportedbeing flooded for reasons which will be outlined later in this report.Flood risk can be calculated by combining the probability of flooding occurring withthe consequences of that level of flooding. The likelihood of flooding occurring isoften expressed either in terms of a chance (1 in 100 chance of flooding occurring inany one year) or as a probability (1 per cent annual probability of flooding). In thepast, flood risk has been described by a ‘return period’ (such as 1 in 100 years),which could cause confusion when people who have already been flooded believethat they will not be flooded again for a long time. In reality, even when flooding iscalculated as a 1 in 100 year event, there is still a 1 per cent chance of flooding thefollowing year.- 11 -Page 170The PFRA, which was completedin June 2011, indicated that over8,000 properties could be at riskof surface water flooding in a 1 in30 year rainfall event. This couldrise to between 13,000 and29,000 properties in a 1 in 200