Future flood prevention Contents

3Predicting and communicating flood risk

Climate and weather forecasting

35.Effective responses to flood risk require an accurate understanding of both short-term weather patterns and long-term climate trends. English flood management agencies have access to world-leading expertise in both these areas. Witnesses told us that the Met Office provided the “most accurate national weather forecasting service in the world”. Today’s four-day weather forecasts are as accurate as one-day forecasts were 30 years ago and rainfall forecasts are 10% more accurate than they were two years ago.55 Never the less, the Public Weather Service Customer Group, which independently assesses the Met Office service, continues to press for more accuracy in severe weather forecasts and for greater local detail: it told us that Met Office investment in supercomputing capacity was helpful but future improvement depended on continued government funding.56

36.The Met Office is also considered to be a world leader on climate change science. Its projections help inform long-term resilience and associated investment decisions such as the Environment Agency’s Long Term Investment Scenarios. Met Office data is being used to update 2009 climate change scenarios, with more refined models to be published in 2018.57 However, significant uncertainties remain in predicting climate change trends and the impact on rainfall and flooding.58 The NFRR published in September, after we finished taking evidence, has reduced some uncertainties. It concluded that, based on Met Office modelling, it was plausible that rainfall between 20 and 30% higher than normal could be experienced over the next ten years. The Review noted that flooding under these predicted rainfall scenarios would remain “overwhelmingly” within areas defined by the EA as expected flood areas under its Extreme Flood Outlines.59 Some 12% of England lies within these areas.60 Furthermore the NFRR notes that flooding is “impossible to forecast precisely” and the possibility of floods outside the EA-defined areas could not be excluded.61

Flood warnings

37.Translating data into useful flood warnings requires co-ordination between the Met Office and other agencies, principally the EA. Weaknesses identified by the Pitt Review, set up in the aftermath of the 2007 floods, have largely been addressed by measures such as the establishment of a joint EA/Met Office Flood Forecasting Centre.62 Witnesses considered this to be an effective approach. However, some were concerned that the EA’s local flood risk maps contained limited information and failed to indicate, for example, depth of flooding. The next generation of such maps will include not only current but also future risk, accounting for climate change.63 During our visit to Somerset the EA demonstrated a new IT system which feeds real-time monitoring data from river gauges into the systems used by staff operating flood incident rooms to collate and issue flood warnings for communities.

38.The Environment Agency and the Met Office are working effectively to improve flood warning systems, including developing innovative ways of using real-time data in some places. However data sets need to be improved and new systems need to be used in catchments across the country. We recommend that the Environment Agency report by July 2017 on how it can work with the Met Office to collect more detailed real-time data on rainfall and river levels. We further recommend that systems such as those being developed in Somerset to feed real-time data into live flood forecast warnings are deployed across England at the earliest opportunity.

Public understanding of flood risk

39.Public acceptance of the need for individual, local and national action on flooding requires an understanding of the level of threat. Communities which have recently flooded are all too well aware of the risk to their homes and livelihoods. We heard during our visit to Somerset how effective local flood wardens were in communicating flood risk to their communities. But in advance of a flood, public awareness can be low: the EA told us that although nearly half the population surveyed in recent research reported being aware of a local flood risk, only 7% felt this risk applied to their own property.64

40.Part of the lack of awareness stems from the way in which flood risk is communicated. Evidence to this inquiry on the issue was almost universal in criticising the use of the current formulation of explaining flood risk to the general population. Although flood risk professionals understand it, the “1 in 100” year formulation is not effective in communicating flood risk to the general public. The NFRR notes that this formulation is likely to be misinterpreted.65 However, witnesses also saw alternative statistical methods (such as citing a percentage risk) as flawed.66 In general, witnesses preferred the use of a simpler approach such as a traffic light system, with red indicating a high flood risk, or a broad categorisation such as ‘high flood risk’ or ‘low flood risk’, but no one formulation can offer the perfect answer. Natural Resources Wales noted that “in raising awareness of flood risk [it is important that] we focus on communicating that there is a risk (rather than specifying exactly the level of risk) and crucially what can be done about it”.67

41.Defra’s Parliamentary Under-Secretary of State, Dr Therese Coffey, conceded that there was a “communication challenge” to address, noting that although the EA had expanded flood warnings to some 1.3 million people, some of the language needed to change so that risk was “readily understandable”. She noted that the EA was piloting new approaches.68

42.Current methods of describing flood risk using the ‘one in x year’ event formulation are confusing. It is hard to interpret from this information the risk of flooding for any particular home or community at any particular time: individuals may not therefore appreciate that they need to take steps to reduce their own risk.

43.A poor grasp of flood risk also hampers wider public acceptance of the inevitability that there will frequently be flooding somewhere in England. Without this, it will be difficult for flood risk bodies to gain acceptance for their plans: this acceptance is vital since the increasing risk of flooding means that tough decisions must be made about how much to spend on protecting communities from floods.

44.Flood risk agencies must find clearer ways of explaining flood risk, to spur both householders and businesses to prepare effectively for floods and to inform public views on national and local flood risk strategies. We recommend that the Met office and the Environment Agency set out by the end of 2016 a simpler system for explaining flood risk. The EA should also publish maps which include not only whether a place is at risk of flooding but also the likely depth of flood water and duration. These maps should show risk from all types of flooding and be available at one website address.

55 Dr Wyn Williams, Chairman of the Public Weather Service Customer Group (FFP 32) para 3

56 As above

57 Met Office (FFP 46) para 8

58 South West Water (FFP 49) para 1.5

59 HM Government, National Flood Resilience Review, September 2016, Executive Summary

60 HM Government, National Flood Resilience Review, September 2016, para 1.3.1

61 HM Government, National Flood Resilience Review, September 2016, para 1.4.3

62 Sir Michael Pitt, Learning lessons from the 2007 floods, June 2008, recommendation 4.70

63 Environment Agency (FFP 128) para 2.3

64 Environment Agency (FFP 128) para 1.4

65 HM Government, National Flood Resilience Review, September 2016

66 For example, Cyfoeth Nauturiol Cymru/Natural Resources Wales (FFP 149) para 2.3 and Scottish Environmental Protection Agency (FFP 148)

67 Cyfoeth Nauturiol Cymru/Natural Resources Wales (FFP 149) para 5.2

68 Q618

28 October 2016