[2023] UKUT 00282 (LC)

The account given here is taken from the parties’ agreed chronology, from the factual evidence of Mr and Mrs Brookhouse (whose evidence was entirely unchallenged), and from the evidence of other witnesses, all of it unchallenged except where we say otherwise.

The King’s Lodging and its environment

The King’s Lodging is a Grade II listed building. There has been a building on the site for nearly a thousand years, but the present structure dates from certainly the early sixteenth and possibly the fifteenth century. It stands in a third of an acre of ground; the house fronts directly on to Stour Street and there are gardens between the house and the river Stour which runs roughly parallel to the street. There is a swimming pool at the north end of the garden. At the south end of the property is a garage, and on the river side of the garage is a dock. The building is beautiful, and is of course of great historical importance; the gardens are well kept and most attractive save for the former working strip parallel with the river wall, which has been left in a desolate state.

The following aerial photograph shows the orientation of the The King’s Lodging and its garden from north-west to south-east, and shows how the river wall ends north of the eastern corner of the property; the wall on the north side of the dock is significant and we refer to it as the return wall of the dock.

The old wall is not a particularly old feature. A photograph from 1936 shows a timber wall, and the claimants’ expert hydrology witness Mr Evans expressed the view that a line on the 1872 Ordnance Survey may indicate a yet earlier wall, closer still to the house.

The river Stour is tidal. Its water is therefore saline, and of course it rises and falls twice a day. Sandwich stands in the flood-plain of the river on low-lying ground, not far from the sea; roads are typically 2m or 3m above Ordnance Datum (or “AOD”, meaning approximately above sea level (Footnote: ²)). Ground elevations at the base of the river wall are between 2.9m and 3.2m AOD, between 3.3 and 3.4m AOD on the lawn between the house and garage, and between 3.14m and 3.46m adjacent to the main building.

In 2011 the claimants asked the respondent for a flood risk report for their insurers. The respondent’s report in December 2011 said that the floodwall at the property boundary was “in quite bad condition, with some seepage occurring on high spring tides which does wet the garden. However this seepage is unlikely to directly flood the property”. The report noted that the height of the flood wall was such that there was a 1/20 to 1/50 (meaning once in 20 or 50 years) flood risk as a result of the risk of overtopping at neighbouring properties.

In 2013 the Xaver tidal surge occurred. (Footnote: ³) The claimants were not present at the property, but Mr Brookhouse was told by neighbours that water entered The King’s Lodging from the neighbours’ gardens and from Stour Street, and that the river wall was over-topped for a time. The claimants visited a few days later and found that water had entered the house. Mr Brookhouse said that Xaver was unique in the claimants’ ownership; otherwise they had no problems with tidal ingress or flooding and their tenants did not report any (the claimants have occupied the property irregularly and at times it has been let, although not since before the start of the works). The gardens tended to be dry and the land was not boggy when they were in residence.

The flood defence works at The King’s Lodging in 2014

The Sandwich Town Tidal Defence Scheme was conceived as a result of the respondent’s Strategy Approval Report for the Pegwell Bay to Kingsdown Flood and Erosion Risk Management Strategy in 2008, from which it emerged that the protection of Sandwich from flooding was a priority for the respondent because of the number of properties at risk of flooding from a “5% annual probability event” (meaning water levels rising to a level of which there is a 5% probability every year). So said Mr Ian Nunn, the respondent’s Operations Manager for East Kent, who gave evidence of fact and provided a wealth of detail about the extent of the Sandwich scheme, which he described as the largest flood defence scheme in Kent for three decades, and about its planning and execution.

The river wall at the property before the works was described by Mr Nunn as “a timber retaining wall with random concrete cladding, … in a poor condition with a high risk of failure”; the respondent considered that The King’s Lodging was at substantial risk of flooding and needed to be included in the Sandwich scheme. Extensive planning and consultation preceded the work, and the necessary consents were sought, for example, a licence from the Marine Management Organisation, a licence from the Sandwich Port and Haven Commissioners, listed building consent and planning permission. From Mr Nunn’s and Mr Brookhouse’s evidence we learned that a number of discussions took place with the claimants and their concerns were listened to. CH2M (formerly Halcrow) were the engineering company appointed by the respondent to provide consulting, design, construction and operation services on the project, and they made a number of revisions to the plans following the discussions.

Mr Nunn explained that it is unusual for the respondent to enter into a deed of agreement with landowners but, in this case, the claimants wished to set out the agreed terms between them in a formal deed and the respondent considered it pragmatic to do so. The deed is dated 6 November 2014 and covers a number of matters including the claimants’ consent to the installation of vibration monitors, and obligations on the respondent to carry out a “full drain survey” prior to entry for the works and to carry out landscaping works of restoration, including replacement planting.

The work commenced in November 2014. The new wall of steel sheet piles (SSPs) was installed about 1m outside the old wall, with a concrete wall or capping beam on top. The old wall was knocked down to below ground level, and the gap between the two walls was filled with free draining material to a depth approximately 0.75m below ground level. A 1.3m wide reinforced concrete slab or apron was added to bridge the gap between the old and new walls. This was described by Mr Jon Holland of CH2M, in his review of 19 October 2016, as a “…cut-off arrangement [is] to prevent significant seepage into the garden in the event that the free draining material does fill with water.” The new wall was not intended to be impermeable and Mr Holland explained in the review “…the design aimed to retain a degree of connection, below garden level, of the tidal influence of the river with the natural groundwater regime in the garden subsoil.” The clutches between the SSPs were left unsealed and flap valves were placed at intervals to ensure that water could flow out of the garden and into the river (as it was known to do through the old wall), albeit not at a rate that would cause the land to dry out. The work was completed in January 2015, save for the reinstatement of the garden. Mr Nunn explained that the river frontage at The King’s Lodging is about 53m long, and so represents about 4% by length of the flood defences built as part of the scheme.

Below is a diagram showing the essence of the scheme in its early stages, without the concrete slab which now sits over the semi-permeable fill between the two walls.

The effect of the work was to extend the claimants’ land by a short distance, by placing solid material where there had been water. The land under that water was part of the foreshore and so belonged to the Crown, and so in order to regularise ownership a strip of the foreshore was transferred to the claimants on 18 July 2016.

As we saw above (paragraph 13), the riverside edge of the claimants’ garden turns inwards to the dock at its southern end. The sheet piling extended along the edge of the garden but did not turn inwards along the dock return wall. The junction of new and old in that corner was to prove a major headache in the months that followed the completion of the work.

The garden inevitably suffered as a result of the work; while much of it was untouched, a strip on the landward side of the old wall became a working corridor in the course of the works. Some of it has been excavated, and then the excavations filled. The plan is to add topsoil over both the corridor and the concrete apron itself, so that the garden extends to the new wall. This has not yet been done; the respondent proposed to do it in 2017 but the claimants did not allow it because of their continued concern about water ingress.

Water ingress and remedial work from 2015 onwards

Over Christmas 2014 and in January 2015, around the time of completion of the works, Mr Brookhouse witnessed significant water ingress to the garden through the gap in the corner where the SSPs did not meet the return wall of the dock. Remedial work was carried out by CH2M to seal the corner using a concrete “gravity plug”, meaning a block of concrete resting on the bed of the river in the gap between the dock wall and the SSPs.

However, water ingress continued and at a meeting on 25 March 2015 between Mr Brookhouse, Mr Nunn, and another of the respondent’s officers it was acknowledged that the problem had not been resolved. Subsequent work in November 2015 included reinforcement of the tie-in between old and new walls by welding a steel plate at the junction and plugging the gap with cement grout.

In December 2015 Mr Brookhouse recorded “more water than ever pouring into the excavations”. Water ingress occurred again in January and February 2016, which led to further investigations by the respondent and CH2M, and further remedial works in the corner to the dock wall in May and June 2016. These works involved welding, at low level in the river, gaps between piles and steel plates, and injecting cement grout into the free draining material over a length 5-10m north west of the dock corner and below the river bed level at the location of the tie-in. The pre-works sheet piling in the dock wall was reinforced with a concrete slab on its landward side.

By August 2016 the respondent was notified that water ingress was still happening at high tides. There followed yet another round of investigations and technical reviews by CH2M in the autumn of 2016. CH2M’s technical review, produced after observations of the spring tide on 18 October, said:

“… measures implemented for the scheme should ensure river water does not enter the garden, even during extreme tidal flood events.” (Footnote: ⁴)

The review concluded that assumptions made about the level of water ingress through the SSPs had been optimistic, and that water ingress through the free draining material from the SSP clutches was greater than anticipated. CH2M took the view that the flap valves might not be operating correctly and that the hydrophilic seals between the SSPs and the outside of the concrete wall had failed.

In January 2017, water ingress occurred yet again and we saw a video of water flowing through a crack in the new concrete wall, immediately below its brick cladding to the landward side. Meanwhile, design proposals for the further remedial works were being drawn up. The proposals were to seal the apparent leakage path between the outside of the old wall and the base of the new reinforced concrete wall along its whole length by means of a proprietary waterproof membrane, above which would be a reinforced concrete slab. The membrane would extend at least 1m down the landward side of the old wall and be kept in place by compacted clay. The proposals also included the removal of some of the flap valves and improvement of others by use of ‘duck-bill’ valves. The work took place between May and July 2017. It is notable that no further work was done to seal the dock corner. By this stage Mr Evans, of Evans & Langford LLP, had been appointed as consulting engineer to the claimants; in a letter to Mr Nunn, dated 12 July 2017, Mr Evans said:

“…the implication is that the old wall, badly damaged during demolition, has become the actual defence and the new sheet piles will be doing little more than support the new capping.”

Mr Evans expressed concern at the time that the waterproof membrane would not work because it was placed against the rough and broken surface of the old wall and not against a smooth surface as specified by the manufacturer.

The respondent’s contractor’s on-site diary indicates that in the course of the works in May 2017 a section of the old wall (already taken down to below ground level) broke away leaving a gap below ground, and the diary includes photographs in which the gap is visible. It was temporarily covered with sheets of wood. The diary mentions a plan to concrete over the gap but there is no record that this was done.

A final water ingress event occurred in January 2019, which we also saw on video. Water was shown to be seeping from the new river wall, along the whole length of the garden adjacent to the river, at the interface between the brick cladding to the new wall and the concrete slab constructed in mid-2017. The water could be seen seeping out from various points, then running over the concrete apron to pool in the unrestored working corridor in the garden. Bubbling was evident in the standing pools.

No further flooding has occurred since. The respondent’s pleaded case was that the problem has been resolved and will not recur. However – to anticipate our discussion of the expert evidence below – the respondent’s expert witness on hydrology concedes (and the claimants' expert agrees) that they will recur in future when the river levels at high tides exceed 3.1m AOD, which (significantly) they have not done since January 2019. We refer to those inflows caused by tides above 3.1m AOD as the “extra-high tidal inflows”, with apologies for the inelegant expression but it is vital to distinguish these inflows from the seepage that occurs regularly at high tide twice a day.