• Residential flood damage is significant in almost all cases of serious flooding in the UK, and remains an area of public and government concern.
• The scale of property damage will vary between events; during the Easter 1998 floods, approximately 2,500 households experienced flooding, whereas in Autumn 2000 this figure was nearer10,000 and 6,000 for the Summer 2012 floods. The summer 2007 event led to the flooding of some 40,000 residential properties.
• For most events, damage to residential property is the largest single contributor to total damages (approximately 40% for Summer 2007).
• Approximately 5 million properties in England and around 350,000 in Wales are at risk of flooding.

Property

• In the UK, the vast majority of residents live in a terraced, semi-detached or detached house or a flat or bungalow. The age and style of these properties vary, as does the building fabric and contents.
• The potential damages associated with a certain flood depth inside a building are calculated using a depth-damage relationship. This is a chart or ‘curve’ where the increasing damage to a property is shown against the increasing depth of a flood. These curves are available from the MCM-Online.
• We can assess the likely cost of damage to all of these property types from floods in the future, taking into consideration the age of the property.
• The potential damage values provided are for the typical sized property in the UK, but also in pounds per square metre (£/m²) to account for regional and local variations in size.
• The duration of the flood will usually have an impact on the damage caused, and so the data available takes into consideration different flood durations. Other residential property related flood losses Include:

Temporary and alternative accommodation

• There is a link between the depth of flooding and the amount
  of time people have to leave their homes for whilst repairs are done. It is possible to estimate the approximate costs of evacuation to each flooded household for different flood scenarios and durations. The Professional Section of the MCM-Online provides these figures at three different levels of complexity. To calculate the costs associated with evacuation, it is important to consider:
• the temporary accommodation (hotel, B&Bs etc in the immediate aftermath);
• the alternative accommodation (longer-term rental of accommodation);
• the additional spending by those evacuated on pre-prepared food and travel to/from their place of work or the flooded property;
• the loss of earnings from needing to take time off work.

• There are approximately 200,000 Non-Residential Properties (NRPs) in England and Wales at risk from river or coastal flooding.
• NRPs include high street buildings (traditional retail outlets, banks, public houses); traditional-style buildings (offices, schools, libraries); industrial-style buildings (warehouses, supermarkets, sports centres, manufacturing plants); modern framed buildings (office blocks, community centres); health and religious buildings (hospitals, churches); and others (car parks, electricity sub-stations, playing fields).
• Flood damages to NRPs can form a significant part of the total bill following a flood event. For instance, impact to business represented 23% (£740 million) of the total estimated economic costs of the summer 2007 floods in England.

• As the variability between NRPs is so vast (consider, for example the variance between high street shops, supermarkets, hotels, banks, warehouses, factories, school and hospitals) the use of depth-damage curves (i.e. the potential damages associated with a certain flood depth inside a building) for different types of NRP are required to reflect this variability.
• These depth-damage curves are then averaged into the main property types: Retail, Offices, Warehouses, Leisure and Sport, Public Buildings and Industry.
• All depth/damage data for NRPs are in pounds per square metre (£/m²), so the area of the ground floor space of the sub-sectors and categories is required.
• The function and size of unconventional or unique properties should be determined, in the first instance, using an online verification tool such as Google Street View and confirmed with a site visit.
• Obtaining accurate data on indirect flood losses is difficult. In an economic appraisal indirect losses should be limited to the losses of business to overseas competitors (national scale point of view) and to the additional costs of seeking to respond to the threat of disruption. It is very difficult to provide standard data for assessing these indirect flood losses and specific case surveys will usually have to be carried out.

• The losses experienced due to the disruption of services and transportation networks will have impacts outside of the flooded area as well as within it, and in some cases the impacts may be geographically far reaching.
• The summer 2007 floods caused widespread impacts to infrastructure in England and Wales. For instance, the closure of the Neepsend electricity sub-station in Sheffield caused a loss of power to a population of around 40,000 people.
• The closure of the Mythe water treatment plant left a population of 350,000 people without water for over two weeks.
• Environment Agency data suggest that over 18,000 electricity assets (7 per cent of all national assets) and 1,400 sewage treatment-related assets (25 per cent of all national assets) are at moderate to significant flood risk in England and Wales.
• In addition, many vulnerable groups are located in at-risk areas, including over 1,000 care homes (with 30,000 residents), and 1,600 schools (7 per cent of all schools nationally) with a total of 500,000 pupils.