Surveying for PLP works
Using an external surveyor such as Warwick York, who is independent of the supply and installation steps, can be important in raising trust amongst the recipients of
flood protecion and resilience.
Organisations such as the Royal Institute of Chartered Surveyors (RICS) and the Royal Institute of British Architects (RIBA) have lists of suitable surveyors. No accreditation exists for performing
flood risk surveys. However, RICS offers professional development courses and have dedicated regional groups to equip chartered surveyors with relevant professional skills for flooding and the
ability to deal with specific local issues. Clients and Project Managers could ask for evidence of such continuing professional development as membership of relevant professional organisations
requires this. Warwick York are members of the RICS - all our surveyors are MRICS qualified with extensive experience in flood risk surveys and project management
What should a flood risk mitigation survey include?
The quality of any survey is dependent upon good, and up-to-date, awareness of the type and frequency of flood risk for a given area. Flood risk mapping data continually evolves and so it will be
important to periodically reassess the risk from all sources of flooding when new data becomes available, when new flood risk management strategies are implemented, or when other flood risk variables
are altered (for example, if there are land use changes or a new development is approved).
Different types of flooding
When assessing the flood risk profile of a property, and how best to reduce this, it is important to know:
The types of likely flooding. The four main types are river, coastal, groundwater and surface water flooding. Flooding may also occur due to sewer
defects or incapacity, or because a reservoir or dam fails. The methods of defence against flooding differ according to its nature. For example, hard defences such as sea or river walls, may be very
useful to defend against coastal or river flooding, but may well make surface water flooding worse (as the water cannot escape to the river) and will be of no effect against groundwater.
How frequent this type of flooding will be. This is often called the flood return period. It is expressed as either:
a ratio (1:30, 1:75, 1:100, 1:200 and 1:1000 are common benchmarks). This means that this amount of water is expected once in 30, 75, 100, 200 or 1000 years.
a percentage. This is just another way to express the ratio. For example, a 1:75 risk could be expressed as 1.33% risk.
There is a common misconception that, where flood risk is defined as a ratio (for example, 1:75) if the property floods this year, it will not flood again for the next
74 years. In fact, it means there is a 1.33% risk of it flooding this badly every year.
How deep the flooding will be. This will influence the degree of damage, the measures that may be effective to keep the water out, and (if deep enough
to present a risk to the structural stability of the property) whether it would be more sensible to allow the water to flow through the building and out again, rather than seek to keep it out.
Action to take if the property is at risk of flooding
A buyer/tenant need not necessarily abort the transaction because it has discovered that the property is at risk of flooding. If the risk is low enough, they may be
happy to accept it without making any contingency plans. Where the risk is higher, or they are more sensitive to it, then the buyer/tenant may instead wish to consider:
Reducing the purchase price or premium for the lease, leaving money in hand to carry out flood protection measures, to repair flood damage when it
occurs, or to pay any higher flood insurance premium or policy excess.
Planning their use of the property in a way that keeps flood sensitive uses, such as storage of papers, computer rooms and electrical plant, away from
susceptible areas of the property (ground floor and basement levels).
Having a robust plan for how to respond to an impending flood.
Carrying out works to improve the flood resistance or flood resilience of the property. These are called property level protection measures ("PLP
works"). The buyer might require the seller to do these before completion, at the seller's expense:
flood resistance measures slow down or prevent water ingress, for example, installing airbrick covers, door/window baffles, non-return valve plumbing or tanking the
external walls of the property;
flood resilience measures reduce the damage caused to the property by flooding and improve the speed with which the property recovers from flooding. They might involve
replacing woodwork with plastic (in kitchen fittings, doors, skirting boards), using concrete or hard floors instead of wooden floorboards and carpet, using water resistant render rather than
plaster, and mounting electric sockets at height.