Designers, contractors and authorities that neglect to consider the impact of building near rivers could find themselves liable for flood damage caused downstream. Take care.
the year 2000 was the wettest on record in England and Wales. Apart from producing misery for business and the public, the flooding will bring claims against various statutory authorities, architects, engineers and contractors.

In the recent Court of Appeal case of Bybrook Barn Centre Ltd vs Kent County Council (2001 BLR Vol 2), the court was concerned with flooding caused by a culvert under a highway being inadequate to accommodate increased flows in a watercourse caused by substantial developments built upstream. The claimants were the owners and occupiers of a garden centre, through whose land the watercourse ran. Some 46 years before the flood, the watercourse had been culverted under a public highway then being built.

When constructed, the culvert was adequate to accommodate all reasonably foreseeable flows of water. Since construction of the culvert, however, there had been substantial further development, including the construction of the M20 and a business park upstream, so that there was increased run-off of rainwater into the watercourse. The highway authority became aware some six years before the flooding that the culvert was unlikely to be able to take the increased peak flows. Flooding occurred in 1996, damaging the premises and stock.

The owners and occupiers sued the authority for nuisance. The authority argued that the culvert, when constructed, was not a nuisance and that, in any event, the flooding had been caused by the new construction upstream for which it was not in any way responsible.

The court rejected this argument, saying that it was incumbent upon the defendant to take reasonable steps to avoid or limit such actual or potential nuisance. Effectively, the authority should have provided a culvert of greater size once it was – or should have become – aware of the inadequacy of the old one, particularly since the cost of such work was relatively minor.

Planning authorities have been known to ignore, or give insufficient weight, to the risk of flooding because of pressure from planning applicants and the government

Over the past 30 years, a massive amount of housing, road, industrial and commercial construction work has taken place. Over the next 10 years, there is a substantial amount of further construction proposed, particularly housing. Further development inevitably introduces greater run-off of rainwater, which might otherwise be absorbed in the ground.

Architects, engineers, contractors and statutory authorities will need to be aware in designing and constructing building and engineering works how they might be affected by other developments at a later stage. For instance, if a designated local plan identifies that upstream of a construction site new housing or other development is proposed, the designer of premises downstream or downhill should, as a matter of reasonable care, take such potential development into account.

The government has endorsed proposals for massive new housing development, both on green and brown field sites, over the coming five to 10 years. Local planning authorities regularly receive representations from the Environment Agency and other authorities relating to the risks of flooding in respect of proposed developments. However, planning authorities have been known to ignore, or give insufficient weight, to such advised risks because of pressure from planning applicants and from the government.

The law of negligence is complex, if not confusing, in this area, but it may well be the case that a planning authority that permits a development that is likely to cause flooding, which no careful authority should have granted, could be sued for damages if unavoidable flooding causes physical damage to other houses.