7. Assessing social impacts
7.1.1. Flooding can have a wide variety of social impacts, such as impacts on human health and wellbeing (e.g. risk to life, exposure to contaminated water, long term stress and anxiety), loss of irreplaceable items and loss of community. Reference material for understanding the social impacts of flooding is listed in Box 7.1.
7.1.2. Social impacts arise as a consequence of actions to manage flood risk. For example: provision of flood warning can help to reduce worry about future flooding (Werritty et al. 2007); some engineered and natural flood management actions can create recreational opportunities.
7.1.3. Engagement with affected communities can help provide insight into the negative and positive impacts of options by drawing on local knowledge. Local authority social services, community groups and the voluntary sector may also be able to help describe and quantify the impacts.
Box 7.1: Reference material for understanding the social impacts of flooding
7.2. Risk to life
7.2.1. Whilst deaths from the flooding in the UK have fortunately been rare, it is still sensible to assess whether floods in a particular situation pose a high risk to life. Reducing risk to life, therefore, may be a key consideration when comparing options.
7.2.2. Risk to life is assessed using a function of depth and velocity. Defra (2008b) published a method that can be used to calculate the potential number of casualties and also to assign a monetary value to loss of life. Care should be taken to ensure that there is sufficient confidence in the flood hazard data before making this assessment.
7.2.3. There may be significant risk to life to due to local flood characteristics arising from wave overtopping. This is not considered in the Defra (2008b) method and so should be considered on a case-by-case basis.
7.3. Flood impacts on human health
7.3.1. The short and long-term health impacts of flooding may be significant, especially for vulnerable households, but can be difficult to quantify in monetary terms.
7.3.2. Guidance provided by Defra (2004) indicates that the value of avoiding the health impacts of flooding is of the order of £200 per year per household. This value (uplifted to present day values) can be used for more strategic appraisals. For more detailed (feasibility and design) appraisals, where information on baseline and 'do something' standard of protection is known, Defra's (2004) risk reduction matrix may be used instead.
7.3.3. The values published by Defra (2004), however, should be used with caution as they capture only part of the intangible health benefits of reducing flood risk and are likely to be an underestimate. This is an evolving topic of research and new values may become available (See discussion in the MCM).
7.4. Social vulnerability to flooding
7.4.1. Different people will vary in the degree to which their health and wellbeing would be negatively affected if they are exposed to flooding. A body of research has identified a range of factors (e.g. age, health, income, home ownership, housing type, green space) that can influence flood vulnerability (e.g. Kazmierczak et al. 2015; Lindley and O'Neill 2013; Houston et al. 2011; Tapsell et al. 2002).
7.4.2. Recent research commissioned by the Scottish Government has examined social vulnerability to flooding in Scotland (Kazmierczak et al. 2015). The research has produced maps of social vulnerability and flood disadvantage: these are available as GIS files and can be used to help understand the nature of the flooding problem and to support and evaluate flood risk management decisions.
7.5.1. Some flood risk management options may affect the value of a river or the coast for recreational uses. For strategic appraisals, an assessment of impacts on recreation is likely to be qualitative. At more detailed (feasibility and design) stages of appraisal and where there are significant gains or losses, impacts on recreation should be included in the benefit-cost analysis as far as possible. Where only marginal changes in recreation or amenity are likely, such valuations will seldom be worthwhile. Further advice on considering such impacts is provided in the MCM.
7.5.2. Note that where recreational value is a significant part of the total benefits, a contingent valuation study may be necessary to derive a site-specific value of enjoyment. These studies, however, can be complex.