Identifying/managing the flooding risk at a property

The purpose of this section of the guide is to provide advice for:

++identifying if there is a risk of flood to a property

++establishing the level of flood risk to a property

++managing the level of flood risk to a property

Floodwater will be contaminated in one form or another, ranging from sediments, soil, organisms, dissolved substances, and , more worryingly, chemical wastes and effluents etc which can be particularly destructive.

The nature of the contaminants will affect the speed and cost of cleaning and of restoring premises to their original condition.

Floodwater will not just enter a building through door openings. More often than not water will penetrate - and pass through or round - the building fabric (e.g. walls, floors and other major structural elements), cavities, air bricks, horizontal pipes, waste water fittings, sewage pipes, drains, floor gullies etc.

Fig_83 Inside the pottery at Boscastle (UK) following the August 2004 floods

Susceptibility of contents and equipment

Once floodwater enters a property the scale of the loss will increase dramatically.

Domestic contents are very susceptible to flood damage and in many instances the contents of the ground floor are totally destroyed. The susceptibility of the contents in commercial premises will vary greatly, but even the most robust equipment is likely to suffer some form of damage ranging from partial corrosion (and other forms of material deterioration) to total destruction.

In many instances the property does not even have to be permanently damaged for the insurer to incur costs, as most losses will involve an element of cleaning and decontamination. It is also not uncommon for otherwise undamaged property to be destroyed and replaced purely because the costs to decontaminate and repair are uneconomic or because of a requirement to do so under health and safety regulations.

Susceptibility of buildings and fittings

Most modern domestic and commercial buildings in the US and UK were not built to withstand flooding (although some improvements in this particular area are being introduced).

Depending on severity, flooding can render a property unusable and bring normal household or business activities to a halt. Even when it has subsided, floodwater is likely to cause contamination to buildings and fittings, and it may be visible and odorous. More specifically, contamination can affect a building in the following ways.

++Concrete can absorb huge quantities of water and , until completely dry, cause ongoing problems such as chemical reactions and fungal growths affecting both the structure and contents

++Cavity walls are often lined with insulating materials which may deteriorate if they absorb floodwater

++Floors of absorbent chipboard laid over foam insulation and a sheet of polythene act like a reservoir, holding water in and above the materials

++The chemical action of salts in some floodwaters can affect brickwork, particularly in older buildings, compromising the damp proof course and setting up long term damp problems

++Organic contamination (e.g. silt) is associated with most floodwaters and brings with it issues of hygiene, possibly indicated by an offensive odor. Moreover, fine silt particles contained in floodwater have a tendency to settle in layers in floor voids, and in cavity walls where it renders damp proof membranes ineffective

++Electrical installations that have been subjected to water penetration or even moisture are susceptible to failure. Provided equipment and circuits have not been damaged by floodwater, they may be dried out - absolutely thoroughly - and tested before switching power back on

++Gas and oil meters and boilers may be affected by floodwater, in which case they may require purging and appropriate drain points being fitted.

Risk surveys

Insurers' risk advisers are not qualified hydrologists or structural engineers. Although insurers do have some limited in-house risk management experience, they are not able to offer formal risk management services to policyholders beyond standard survey recommendations.

Insurers therefore recommend that a policyholder obtains professional advice, and this can only be given by those possessing appropriate and recognized professional qualifications such as a qualified hydrologist or specialist building surveyor recognized by the Royal Institution of Chartered Surveyors.

A characteristic of any large volume of water is that it will always find the weakest point into any structure, and that by reducing the risk in one location will potentially increase it in another. Any mitigation or alleviation measures should therefore be considered in the context of managing the risk of the whole property and their potential impact on the wider environment and not just the originally expected point of entry. This is especially true for those buildings in multiple occupation which are spread over large sites or areas; in these circumstances insurers recommend that the property owners would benefit from a more detailed 'catchment assessment' or 'hydrological survey'.

These services are commercially available but insurers tend not to specifically recommend any preferred suppliers and normally suggest that the policyholder contact either their local Environment Agency office or local authority for guidance.

Some of the key elements are considered below.

Identifying the locations at risk.

The nature and pattern of flooding has altered in recent years. Man-made physical changes to the landscape and environment, and changes to weather patterns, has resulted in unprecedented events both on and beyond existing floodplains.

While the causes of flooding events may differ between locations, a level of risk from flooding may exist in a significant proportion of properties.

Identifying the sources of potential flooding

The starting point of any risk management process is to identify the sources of risk.

Flooding can occur from any open or enclosed watercourse, by natural or man-made causes, but more commonly in combination.

The proximity and relationship between buildings and the following sources should be understood:

++open sea -- estuaries, harbors, docks, quays etc

++fluvial -- rivers, streams, brooks, lakes, reservoirs, dams, open drains and ditches etc

++pluvial -- sewers, storm drains, culverts etc.

Identifying the responsible parties

The above sources could be owned, managed or maintained by a number of different parties:

++local authorities

++the Environment Agency

++water authorities

++private land owners

To ensure that any potential problems (eg damage, blockages and failure) can be dealt with quickly, contact details for the each of the responsible parties should be obtained and kept at hand by the property owner.

Establishing the level of risk

Many authorities and agencies have carried out, or are carrying out, risk assessments and evaluations for the watercourses under their control.

These organizations should be able to provide assessments on the potential frequency and severity of flooding along with details of any maintenance and improvements programs they have in place.

Factors that could reduce the level of risk

++Watercourses and drainage systems in the area are unobstructed and well maintained

++Buildings as a whole are situated in a position of raised ground and would not be totally or partially cut off in the event of flooding in the surrounding area

++The properties are serviced by pumped drainage and sewerage systems.

Factors that could increase the level of risk

++Buildings are not protected by adequately constructed and maintained defenses

++Watercourses and drainage systems in the area are obstructed or poorly maintained

++Any part of the premises is situated in a low lying area of ground

++natural or man-made drainage is inadequate for its size, type and use

++Surface water is unable to percolate through ground where it has been covered with large areas of impervious materials (e.g. car parks and large paved areas)

++Surface water run-off risk for premises is located at the foot of raised areas of ground or high land (e.g. embankments, hills and mountains)

++Premises are situated in a position of raised ground and total or partial access would be prevented in the event of flooding in the surrounding area.

Managing the risk

Flooding regardless of depth or frequency is very disruptive both economically and in terms of the health and well-being of the property owners, tenants and employees. Insurance is not able to reduce all the effects and in cases of the most onerous risks is not available.

Once floodwater comes in contact with the fabric of a building it's only possible to slow its ingress. The water will find its way into the building through the weakest point so it's therefore not only necessary to prevent water from entering the premises via doors and windows, but also via drains and sewage outlets, cavities and , in instances of prolonged inundation, through the external brickwork and internal floors.

Floodwater is likely to be contaminated and may result in some property that would normally be salvageable having to be destroyed. While it's not always possible to prevent flooding its effects may be reduced or managed.

The following are examples of the actions that may be appropriate.

Permanent changes and actions

++Relocate, reposition and raise furniture, equipment and valuables to areas well above the expected water levels (e.g. from basement or ground floor to first floor, or raise up on racking etc)

++Replace susceptible wall linings, furniture, fixtures and fittings with waterproof alternatives (e.g. stone or plastic floorings, tiled or water resistant wall coverings, water retardant plasters and linings)

++Reposition electrical points and other essential utilities to heights well above the expected water levels or at maximum heights for comfortable use

++Ensure that power to security systems and essential equipment can be maintained during flooding

++Relocate or reposition safes and strongboxes above expected water levels

++Consider installing one-way or pumped valves to waste outflows

++Store and maintain flood defending equipment and supplies above the expected water level or in a location away from the expected flooding

++Consider using temporary flood protection to slow the ingress at weak points in and around the building (e.g. sandbags and flood boards). Drain stoppers can be used to prevent drainage systems silting up, remembering that they should be removed after the flood has subsided.

For existing properties that are at a high risk of flooding, structural solutions may be the only option; in these cases the involvement of the local planning authority is likely to be required as well as the services of a specialist engineer.

Details on structural solutions, for both new and existing buildings, can be found in:

++in books on preparing for floods

++on the web

The more permanent changes that are made, the easier it will be to deal with a flooding event, especially if there is little to no warning.

Flood event procedures

It is recommended that homes and businesses at risk should introduce a formal plan that outlines the personal roles, responsibilities and actions to be carried out in a flooding event.

The plan should be kept in a water-resistant container in an easily accessible location that's known by all occupants and keyholders and should contain:

++important contact details (e.g. for Environment Agency local office, local authority, insurance adviser or company, and property owners)

++a list and location of items that should be moved above floodwaters

++a list and location of items that can't be moved but should be enclosed in watertight bags or containers

++a list and location of items that should have their power sources isolated or disconnected

++location of gas and electric isolation cut off points and switches

++location of flood defending equipment and supplies

++a list of weak points for items such as toilets, and washing machine and dishwasher waste pipes in and around the building that would need to be protected by sandbags or other suitable alleviation products

++a list and location of vehicles, boats and other external equipment that can be moved from flood risk areas or secured

++evacuation instructions.

Flood defending equipment and supplies

It is recommended that the following equipment is made readily available to assist in dealing with a flooding event:

++sandbags and flood boards or other alleviation products

++watertight plastic bags (varying sizes)

++shovels

++torches and spare batteries

++waterproof clothing and footware

++spare warm clothing

++protective clothing including gloves and boots (for potential contaminated floodwater situations)

++battery operated radios to monitor flood warning announcements

++mobile phones

++first aid kits

++vacuum flasks and energy foods.

Actions to take before and during a flooding event

Once a flood warning is received:

++flood event procedures should be put into operation

++flood warnings and announcements on the radio should be monitored.

Actions to be taken after a flooding event

Once the all clear is given, advice should be sought on how best to handle the clean-up operation. This should be obtained from:

++the insurance adviser or company

++the local authority

Using flood protection products - a guide for purchasers Purchasing flood protection products should be regarded as one element of a comprehensive flood preparation plan for a particular property or group of properties at risk of flooding.

Various non-profits orgs are committed to helping purchasers of flood protection products to identify suppliers and products that meet agreed standards - products that have been independently tested and that conform to specification. Flood-protection products offer a more effective means of limiting the passage of floodwater than simply using sandbags. They generally allow time for possessions to be moved above the flood level and for other damage limitation plans to be put into action.

In a flood it should not be assumed that there would be no water seepage through the building fabric (ie through the brickwork, cavities, floors and drainage systems etc). Flood protection products are intended to limit the passage of water through building openings over which they are installed (eg doors and windows).

Any manufacturer can claim conformity of their products to a standard but it's their responsibility to ensure any claim is not misleading. Using the specification number on the product, on an attached label or on its packaging is solely a declaration of conformity by the manufacturer.