FLOODING

Summary of this section (updated August 2025)

Obtaining a remedy for flood damage – causation as an initial hurdle in flooding claims – general principles governing the management of water built up over many years must be factored-in – the measured duty of care – the ‘common enemy’ defence – defences of ‘statutory authority’ and of ‘statutory compensation’ – the defence of statutory inconsistency’ (Marcic) – a note on water pollution

Note: general rules and principles relevant to the following will be found elsewhere on these pages: (i) who can constitute a claimant, (ii) defences and (iii) remedies.  Flooding and water claims are subject to certain specific defences which are considered in more detail below. 

Introduction

Flooding claims arise in respect of a wide variety of factual contexts, for instance, in connection with the management of rainfall, groundwater, drainage and sewage.

Obtaining a remedy for flood damage is challenging for a claimant. This is for a variety of factual as well as purely legal reasons.  In anything other than a simple claim, an expert report as to causation is likely to be required.  General principles relating to water also need to be considered, the law in this area having developed incrementally over very many years.

Water is an unpredictable and natural resource, as well as a ‘common enemy’.  The courts have been reluctant to make a party liable for dealing with flood water, there being a limit to the extent to which it is possible to protect land without diverting the problem elsewhere.  Parliament has also placed practical limitations on the resources which have to be spent by bodies with statutory responsibilities in relation to water.

One specific defence in respect of water and sewage flooding is that of ‘statutory inconsistency’.  For many years the courts have held that a claim in nuisance for sewage or water flooding cannot be maintained if the remedy entails the design and installation of a new sewerage system (i.e. the flooding in question is caused by an inadequate system of pipes and sewers). The contemporary law is explained in Marcic (2003), which considers the Water Industry Act 1991.  Accordingly, the defence of ‘statutory inconsistency’ (as this will be known) is set out in this section of the website.

Some other defences regularly respond to flooding claims, and these are to be found in the section ‘Defences’.  In particular there are the defences of ‘statutory authority’ and of ‘statutory compensation’.  As to the first of these, legislation exists which can expressly (or impliedly) exonerate any person or undertaking from its acts and omissions.  As to the second, some statutory provisions expressly provide for compensation where damage occurs (an example being flood damage).  Where there is a statutory right to compensation then the effect may be that a claim in nuisance is excluded as a result of the existence of that right.  These defences are not exclusively connected with flooding claims, which is why they are dealt under ‘Defences’.  For the same reason, the same section considers the defence of ‘Act of God’ and the defence which can apply where the cause of the flooding is the malicious act of a stranger.

Flooding and water damage claims are species of the law of private nuisance which concern property damage where liability is strict (category 1). The rules concerning the characteristics of both the claimant and the defendant are described separately in this site. The law concerning remedies is also set out on other pages.

Establishing causation

As to factual difficulties, establishing causation is likely to be very complex.  It is often sensible for a claimant to confront this head-on, i.e. at a very early stage in the investigation of a claim.  If the damage would have happened in any event (as experience often shows to be the case), then there is little point in pursuing the claim.  This is a frequent problem for claimants.  Save in very straight-forward cases, the cost of exploratory investigations by an expert is likely to be significant (especially if computer modelling is required).

Legal difficulties

As to the relevant legal issues, whilst the law of nuisance governsflooding cases, specific principles relating to water may well have an impact on whether there is a flood claim.  This is because the law establishing such rights has grown up piecemeal over many years, drawing boundaries between circumstances where there is a right of recovery and those where there is not.  These principles are complex  and only a summary can be provided on this page.

Where a defendant has done some positive act to cause flood water, then the general principles of nuisance of the type which have caused property damage will apply.  (This has been described in the introductory section on Private Nuisance as a ‘category 1’ claim.)  The main issues will be ones of causation and foreseeability.

In the case of omissions and in those instances of flooding where the landowner has not done some positive and causative act, then the modern law relating to the ‘measured duty of care’ is likely to be the main sphere of interest (‘category 3’ claims). This is the duty which arises where there has been a failure to act on the part of a landowner who is in a position to prevent or abate a nuisance. The effect of this aspect of the common law is still being worked out, but it has been explored with ever greater frequency by claimants.  See further below.

Another judge-made principle which has enjoyed a resurgence and which is a defence to many flooding claims, is the doctrine of the ‘common enemy’, a principle which may restrict the ability of an aggrieved party to obtain a remedy.

General principles

The following, then, are some summaries as to the legal interpretation of particular factual circumstances.

Where a defendant works its land (A) without negligence and in a reasonable manner, but with the inevitable result that flooding occurs to the land of a neighbour (B), then this is not ordinarily actionable. A practical boundary is drawn between permitting and causing water to flow from A to B, the latter (and not the former) giving rise to a remedy (Smith, 1849, Whalley, 1884 and Home Brewery, 1986).

Where, by some artificial means (such as by building or engineering works), water is caused to flow (or percolate) from land (A) so that it invades (or affects) neighbouring land (B) causing damage, then A may be liable to B (Baird, 1863, Hurdman, 1878 and Home Brewery, 1986). The question, as ever in a case of nuisance, is one of reasonable user (Home Brewery, 1986). Thus, a property owner who built a paved driveway on his land was held liable in nuisance where the result was to divert storm waters on to the property of his neighbour (Bennetts, 1959).

There is ordinarily no liability attaching to water flowing in a natural channel, but if a person interferes with the alveus (for instance by placing it within a culvert), then that person may be strictly liable for foreseeable flood damage (Greenock, 1917). (The alveus is the bed of a river running in a defined channel.)

If the local area changes and the capacity of a culvert which has been installed is no longer sufficient, then a “high obligation” arises to consider whether steps should be taken to ensure that neighbouring properties are not flooded (Bybrook, 2000) (an application of the ‘measured duty of care’ – a ‘category 3’ claim).

If heavy rainfall breaks through or over a person’s land (A) and it damages the land of a neighbour (B), then this in itself does not give rise to any liability on the part of A. However, once flood waters have collected on a person’s land (A), then that landowner cannot undertake works the effect of which are to transfer the misfortune to a neighbour (B). In those circumstances, A will be liable to B: the common enemy principle does not apply (Whalley, 1874).

The ‘measured duty of care’ and its effects in flooding cases

Prior to Sedleigh-Denfield, 1940, a person subject to flooding had few rights where the flooding was not the result of some act on the part of the landowner from whose property the flood waters progressed. By the time of Leakey, 1979, however, it had become recognised that a landowner may be subject to a “measured duty of care” to take reasonable steps to protect a neighbour from the consequences of a natural hazard (such as water), or at least to minimise the risks.  A person whose land has been subject to flooding will want to consider whether this ‘Leakey‘ duty applies to the circumstances which have given rise to the damage. This approach is broader than the ‘general principles’ set out in the previous section.

The duty on an occupier of land is described as a measured duty in acknowledgment of the fact that the occupier has not brought about the nuisance: this is a tort of omission. It takes into consideration the resources of the parties involved and may therefore be satisfied simply by the occupier inviting the affected landowner on to its land to abate the problem (Vernon Knights, 2013 and Lambert, 2010).

A telling factual issue in claims involving flooding in respect of the highway has been the adoption on the part of the defendant highway authority of procedures for checking whether the condition of highway drains has been observed, and the further question whether those procedures have been followed. (See Pemberton, 1960, Bybrook, 2000 and Vernon Knights, 2013.)

The measured duty of care can have an effect on the principles which derive from older water cases: “the tort of nuisance is not to be made the prisoner of precedent” (Green, 2003).

The ‘common enemy’ defence

It is a well-established principle that a landowner has the right to take reasonable steps to protect its land from naturally occurring floodwater, even if it should damage the land of a neighbour (see for instance the coastal groynes in Pagham, 1828).

The right to deflect flood water with impunity is known as the ‘common enemy principle’.  It has been worked out in a variety of contexts.  Thus, in the event of heavy rainfall (or the threat of some other extraordinary flood danger), a landowner is allowed to take steps to protect itself by deflecting that flood water.  It can deflect flood water with impunity, even though the water may cause flood damage to another landowner  (Nield, 1874 and Whalley, 1884).  However, the landowner can only take such steps as are ‘reasonable’ to protect its land by this means (Arscott, 2004).

A line exists which marks a distinction between those occasions when a landowner can protect his land and circumstances when he must accept the damage caused by floodwater without the right to discharge it elsewhere. These circumstances are outlined above within the general principles (see Arscott, 2004).

The common enemy doctrine has been described as a principle of “reasonable selfishness” (Nield, 1874). It has been re-established in a modern context even where the defendant landowner did not consider that it was specifically undertaking works of flood defence (Arscott, 2004).

‘Statutory inconsistency’ and Marcic

It is a complete defence to a claim in nuisance caused by flooding from a sewerage system that the claim is designed only to ensure the installation of a replacement system, i.e a system of pipes and drains which is adequate for the amount of flow.  This principle reached its nadir in the case of Marcic (2003) which concerned the application of the Water Industry Act 1991. Mr Marcic complained that in periods of heavy rain, his front garden was regularly flooded by untreated waste water from the combined sewerage system.

Prior to the House of Lords’ decision in Marcic, a series of cases (for instance Glossop (1878), Smeaton (1954) and Dear (1992)) had each rejected attempts made by claimants to rely on the tort of nuisance as a means of ensuring that a statutory undertaker provide an adequate sewerage supply.  The courts held that, in reality, the claimants’ attempts amounted to applications for prerogative orders of mandamus to compel the public authorities to comply with their statutory duties.  They could not take proceedings in respect of the defendants’ failures to act, their true complaints all being of sewage and water flooding caused by the overtaxing of the sewerage system.  The litigation in each case, as indeed in Marcic, did not concern any positive acts or errors on the part of the defendants.  The only way to rectify an individual flooding problem was to construct a new system for the benefit of the wider locality which was adequate for the task.

In Marcic, an important consideration was the fact that the 1991 Act requires statutory undertakers to weigh up policy issues which had an impact on, and were affected by, funding allocations. The factual problem in Marcic was rectified by a scheme of works in the area which cost in excess of £700,000.  An additional factor is that under the relevant legislative arrangements, a statutory undertaker has limited powers to object to new connections to the system (Barratt Homes, 2009).  A statutory undertaker does not have control of the overall capacity of its sewerage system.  The result is that if money were to be spent on curing a flood issue at one specific address, then all that may happen would be that there would be flooding elsewhere on the system.

In the context of the 1991 Act, then, the relevant principle is that a claim in nuisance is inconsistent with the wider statutory scheme.  Parliament has created a complex system intended to balance the need to ensure that flooding does not take place with the demands on the statutory undertakers’ resources and the priorities which the statutory undertakers need to address.  This is not a function for the courts in a private law action.  The result is that the statutory undertaker has a complete defence.  An important part of the inconsistency arises because there is a regulator with a power of enforcement who exists to adjudicate on complaints about the exercise of the policy considerations (i.e. Ofwat).

In summary, the existence of the statutory scheme described in Marcic, means that individual householders have no right to take common law proceedings in parallel to any complaint to the regulator.  In essence, they have to remain in the regulatory queue, the prospect of remediation being subject to the overall balancing of various different policy priorities and competing claims on the money available to carry out the necessary works.

Marcic has been approved by United Utilities Water Ltd (2024), the effect of this Supreme Court case being to make it generally easier to make claims for the pollution of water by sewerage undertakers (the defence of statutory inconsistency being strictly limited to occasions where the claimant is really arguing about the failure to remediate an inadequate sewerage system). The issue of water pollution (rather than of flooding) is dealt with on a separate page.