Many cases relate to flooding issues that can arise from a multitude of causes, for example faulty drainage (either private drains or public sewers), surface water run-off from developments and changes to land use, inadequate highway drainage, obstructed watercourses and culverts and associated maintenance regimes. Natural fluvial flooding on flood plains is not often a cause for a dispute.
Sewage disposal problems are frequently in connection with poorly performing privately-owned treatment plants and septic tanks, particularly the associated soakaway systems which often turn out be incorrectly designed and constructed.
Some cases are insurance driven: insurance companies may wish to recover monies paid out for flood damage if there is the possibility of the cause arising from negligence. Many private litigations are covered by legal expenses insurance.
In respect of surface water flooding, the law on land drainage is quite complex and responsibilities may be split between the Environment Agency, local councils, highways authorities, water companies and riparian owners of watercourses. It is sometimes difficult to pinpoint a single culprit and a combination of circumstances may come into play. Storm floods may result from acts of God and force majeure: drainage systems are generally designed on a balance of cost and risk and it is not economically feasible to design systems to cater for really exceptional storm events that occur only once in very many years.
The author’s experience of expert witness work over 20 years is believed to be representative of legal activity in the field of water and drainage disputes. That has covered a very wide variety of cases; some were very large involving claims for millions of pounds of damages, but the majority of instructions are for much smaller value disputes between neighbouring property owners or between property owners and drainage authorities and contractors.
In smaller cases proportionality comes into consideration. Clearly it is not worth spending large sums of money on costly investigations and studies when the sums in dispute are not huge, but it can be tempting for technical experts to get carried away with the academic interest and treat the problem with overkill. For example, it is possible for flood investigations to include extensive (and expensive) hydraulic modelling studies.
Also, difficulties may arise because problems often involve buried infrastructure about which there may not be good records. To prove a case absolutely might involve very detailed studies, excavations or specialist internal surveys, but it is essential to keep a sense of proportion. A good expert should be able to arrive at sufficiently accurate conclusions and opinions on a balance of probabilities through a focused approach based on experience, without incurring excessive cost in preparing a report.