Plan Prepare Protect - Floodinfo.ie

Assessing Flood Risk

The easiest way to assess if your house is at risk from flooding is to find out the history of flooding in the surrounding area. For example, your house may be at risk from flooding if it has flooded in the past or if flooding has previously occurred in the locality. If you have not lived in the area long, your neighbours or a local historian might know if any floods have previously occurred.

You can check a number of OPW websites that provide information about flood risk:

Information on past flood events and predictive flood maps are available at floodinfo.ie
Flood hazard maps are available on the floodinfo.ie website.

Another way to assess the risk of flooding in your area is to study the surrounding land and water courses. You could be at risk from flooding if:

Your house is near an open water source, such as a river, the sea, a lake, a stream, ditches or drains.
Your house is in a hollow or a low-lying area where floodwater could collect.
Your house contains a basement.
The Ordnance Survey maps indicate ‘liable to floods’ at the location of your property.

If your property fits into any of the criteria then you could be at risk from flooding due to:

Rainfall filling rivers, streams, ditches and urban drainage systems beyond their flow capacity.
Floodwater overflowing river banks and flood defences onto floodplains.
Coastal storms leading to the breaching of coastal flood defences due to storm surge and wave action.
Blocked or overloaded drainage ditches, drains and sewers overflowing across roads, gardens and into property.
Overloaded sewers back flowing into property.
Rain that is so heavy that run-off flows overland down hills and slopes.
Rain soaking into the ground causing ground water levels to rise and flood.

It is important to remember that while flood defences, such as walls or embankments, do provide some protection against flooding, they do not provide total protection. Flooding of areas behind such defences can occur from water behind the defences being unable to drain away (such as storm water from heavy rain) or from floodwaters spilling over the top of defences in particularly extreme events. If your property is behind a defence, it will flood less frequently than if the defences were not there, but it will still be at risk.

Above Ground

Floodwater can enter your house above ground in the following ways:

Through doorways and windows (even if they are closed!).
Through airbricks or other ventilation openings.
Through other gaps and around pipes and cables that pass through walls.
Through party walls if the property next door is flooded.
Through cracks in the brickwork.
Through permeable, weathered or damaged brickwork, blocks, stone and mortar.
At the damp proof course.

Below Ground

Below-ground floodwater can enter your house in the following ways:

Rising up through the floors (or through the walls of cellars or basements) in areas where the ground is made of permeable material, such as chalk, gravel or sand.
Through drainage trenches in impermeable ground.
Through drains and pipes leading into the house including:
- Toilets
- Sinks
- Baths
- Washing Machines
- Dishwashers

Preparing for a Flood

If you live in a flood risk area you should always have preparations in place in case a flood should happen. Long-term preparations are the best way to ensure that your property is protected against flood damage.

To improve the flood proofing of your walls you can use products such as liquid membranes, polymer/cement coatings, mastic asphalt or pre-formed sheet membranes.
To improve the flood resistance of your windows and doors ensure that the seal around the frames is intact and has no cracks. Also, treat any wooden frames with oil-based waterproof stains, paint or varnish.
There are a range of temporary defences that can be used to protect your house in the event of a flood, such as sandbags, floodboards and wrapping. If you are considering purchasing these products, the information available in the Making a Home Flood Resistant section may be of assistance.
If you are carrying out any extension or building work on your house, it would be a good idea to consider having a waterproof membrane built into the foundations. Also consider closed-cell cavity insulation at ground-floor level and a raised damp- proof course. The electrical sockets should be placed above the height reached by floodwater in previous years and any air conditioning, heating or gas units should be situated on the first floor or in the attic.
Ensure that any streams, rivers or lakes on your property are able to flow freely. Check for blockages in the stream and ensure that the banks have not eroded.
Always ensure that you have a stock of materials which are useful during a flood, such as plywood, plastic sheeting, sandbags (unfilled), sand, nails, a hammer, shovel, bricks, blocks of wood and a saw.
Stay vigilant and regularly inspect your property for cracks or gaps in the brickwork and floors or around windows, doors and pipes.
If you live in a flood risk area it is always a good idea to store any sentimental personal items upstairs or above the highest possible flood level as these are impossible to replace. The same is true of bank and insurance details as well as essential contact numbers.
Valuable items, such as laptops, tablets, televisions, etc. should also be stored if possible above ground level. A laptop, for example, should be kept on the table or desk rather than under it.

Flooding and Business Owners

If your business is in a flood risk area you should have a flood plan in place. Make sure that all staff know what to do in case of a flood.

Be Prepared

Insurance policies – are you insured for flood damage, business interruption and lost revenue?
Make a list of important telephone numbers, including contacts for gas, electricity, water and telephone providers.
Make a list of employees’ contact details in the event of an evacuation. This might include mobile telephone numbers, or numbers for their home or the home of a friend or relative.
Think about staff who may need special assistance in the event of a flood (e.g. elderly or people with a disability).
Incorporate a flood plan into your health and safety plan. Identify evacuation routes for staff. Organise emergency drill (as per fire drill).
Know the location of cut-off points for gas, electricity and water. Ideally, these should be marked on a map that is stored with your flood plan.
Be aware of the location of chemicals, oils or other materials that could be dangerous or contaminate flood water. These should be stored safe from floods and other hazards.

Protective Actions

Note key stock, equipment and possessions that may need special protection from flood waters. Consider backup for IT systems.
Consider things you may need during or after a flood (e.g. sandbags, plastic sheeting, loudspeaker, etc.).
See if it’s possible to move key operations,such as shipping and receiving or customer services, to another building.

Suppliers and External Links

Identify products and services you will need in the event of a flood. Make back-up plans or arrangements for short-notice cancellation of deliveries.
Consider contracting in advance with companies whose help you may need after a flood. This avoids the frustration of finding help in an emergency, and puts you in a better position to negotiate costs.
Identify people who can help you before, during and after a flood.

Making a Home Flood Resistant

If you live in a flood risk area you should always have preparations ready in case of a flood. Preparing a plan for what you should do in the event of a flood is well worth the time it may take – it could save you a lot of money, inconvenience and stress.

Sandbags

It is a good idea to always have a supply of sandbags at hand if you live in a flood risk area. If you do not have sandbags you can use alternatives such as pillow cases or refuse sacks filled with garden soil. Remember not to fill them too early or far away from the site where you may need them as they can get very heavy, very quickly.

When filling a sandbag wear protective gloves as sand is abrasive.
Do not fill the bags more than half full. It is not necessary to tie the ends of the bags, simply tuck the open ends underneath when you are stacking them.
Remove any debris from the area where the bags are to be placed.
Place the half-filled bags length ways and parallel to the direction of the water flow.
Place bags in layers like a brick wall, make sure that in the next layer each bag overlaps the one below by half.
Stamp bags firmly into place to eliminate gaps and create a tight seal.
If you need sandbag protection which is more than three layers high, build them up in a pyramid style: begin with a base more than four sandbags thick and then build upwards, tapering towards the top.
For extra waterproofing cover your sandbag wall with plastic sheeting, making sure to weigh it down with additional sandbags on the ground.

Although sandbags are a popular defence against floods they do have their disadvantages:

During an emergency, sufficient quantities may be difficult to obtain.
They are time-consuming and require two people to fill.
They can be difficult to handle, particularly for the elderly or infirm.
When they come into contact with floodwater, they tend to retain contaminants such as sewage.
Sacking material is biodegradable and can disintegrate if left in place for long periods of time.
Sandbags are not 100% watertight and it may still be necessary to have measures in place for removing water behind them.

Floodboards

Floodboards (or flood barriers) are removable barriers that can be placed across openings, such as doors, in the event of a flood. There are a number of specifically designed, commercially available products that can be bought and fitted. If you buy floodboards, you should look for a product that has a quality assurance mark.

It is also possible to make your own floodboards, although care should be taken to make sure that the barrier is strong enough and that it fits properly in the opening for which it is intended to form a proper seal.

The easiest way to make floodboards is to construct a wooden or metal barrier that is secured flat against a wall, door or across gateways or paths by means of a frame. The pressure of the floodwater itself will help seal the barrier. The efficiency of the boards will be determined by the strength of the walls and the durability of the frame fittings. The most common type of flood board is one which can slide down into the frame, as this can be removed easily when not needed. But you can also make a hinged variety which can swing closed across any gaps. It is important that floodboards fit precisely. If in doubt it may be best to buy specialist items.

Wrapping

Wrapping is an advanced method of reducing the effects of floodwater by enclosing the bottom 600-900mm (2-3 feet) of a property in plastic sheeting.

The process involves digging a trench in front of the wall you wish to protect. The plastic sheeting is attached to the wall above the expected height of the floodwater. It is run down the wall and placed over a drainpipe at the base, before being run through the trench and secured on the other side with weights or sandbags. Wrapping a building takes some DIY ability and needs to be started well before any floodwater arrives as it does take some time. Alternatively there are commercially available products that can be bought and fitted to your property.

Flood protection products can be effective in mitigating against the adverse consequences for properties at risk of flooding. They can reduce the damage caused to contents, furniture and fittings in a house or business, but are not applicable in all situations. In cases of severe flooding (where floodwater rises above 1 metre), keeping water out of your property can be more harmful than letting it in. The stress on the building caused by that amount of water can damage the structure and foundations of the building. Therefore you should never block doors, windows or air-vents over 1 metre in height.

Property owners considering the use of such methods should seek the advice of an appropriately qualified expert on the suitability of measures for their property, and consider the possible requirements for environmental assessment.