East Yorkshire coastal erosion

In the context of East Yorkshire coastal erosion it is not uncommon for a question or suggestion regarding installation of defences against the sea along the entire retreating coastline. The assumption, on the face of it quite reasonably made, is that this would solve the problem of land loss.

early thoughts

The idea is not new. As far back as 1878 Robert Pickwell, an engineer responsible for erecting groynes at Withernsea, gave attention to the matter.

In the opinion of the Author a thorough system of groynes along the whole of this coast would be the most efficient method of protection. [...] Such a system, if commenced at or near the Spurn and proceeded with towards the north, by erecting groynes at intervals of 300 to 400 yards, would secure for the whole of this exposed coast a permanent and sufficient beach. If these groynes were each 300 to 400 feet in length, the cost would be approximately £1 10s. per lineal yard of protected coast... [p211].

While Pickwell describes in some detail the construction of groynes at Spurn, Withernsea, and Hornsea, he does not specify a build that might be employed for a total protection system. Nor does he state a precise extent of coast to be protected or a total cost, but his figure per lineal yard is equivalent to £138.37 per metre at January 2025 prices using the Bank of England Inflation Calculator.

The notion received further consideration in 1905 when Ernest Romney Matthews, then the Borough Engineer of Bridlington, explained the situation of erosion and presented an outline costings estimate for the work of providing protection between Bridlington and Kilnsea.

According to the proposition, 340 long low timber groynes, each of 480 feet (146.3 metres) in length, this being the accepted average cross-beach distance from cliff to low water mark, would be erected perpendicular to the coast, ten groynes to the mile.

At 13s 6d (13 shillings and 6 pence) per linear foot, each groyne would cost £324. For 340 groynes, the amount would be £110,160 [£11,351,787, BoE, January 2025].

Matthews acknowledged that groynes, which he expected to last about 33 years, would not be sufficient. A permanent seawall was also required. Along with cliff cutting and profiling, this would add £19 per yard to the scheme. The total bill becomes £1,247,120 [£128,513,442].

So to the matter of funding, then as always. In Matthews’ words:

The question naturally arises, “Who should bear the cost of these extensive coast-protection works?” It has been suggested that landowners should protect their own land but this is altogether impossible, since the value of the land is only one-third of what it would cost to protect it by means of groynes, which, as already pointed out, are only a partial remedy [pp75-76].

It was Matthews’ opinion that the coast ‘should be protected by Government against the inroads of the sea,’ as in Holland and Belgium.

Debate and discussion followed. Doubts were raised about the ability of the groynes as specified, without land ties or struts, to withstand stormy seas. The existing groynes at Withernsea were stronger but had cost almost twice as much per linear foot, while those at Spurn had been even more expensive. There was a suggestion of engineers ‘cheapening...protective works so as to bring them within the limits of commercial practicability.᾿ Also, multiple groynes would be unsightly and inconvenient.

It was argued that, in the case of Holland, the country was faced with widespread devastating inundation, not the loss of a few feet of cliff each year. Views differed on the reduction of eroded material into the Humber Estuary and to the Lincolnshire coast.

Matthews’ groynes, slightly longer across the beach than Pickwell’s and double the number to the mile, would be £207.46 per metre of coastline (without sea wall, cf. Pickwell’s £138.37).

Groynes installation at north of Withernsea, June 1911 [CCO Withernsea].

recent experience

Perhaps to be expected, the use of timber groynes in the modern construction environment is not necessarily consistent with cost estimates of the past.

In 2017-2018, the replacement of seven decaying timber groynes at Withernsea north amounted to £2,890,000. Supposing average groyne length to be 96 metres (see spreadsheet), cost per metre is around £4,300, including removal of old structures. The lifespan of the new groynes is put at 50 years. A lowering of specification would conceivably shorten the period and be less cost effective.

Groynes replacement at Withernsea. New posts are being piled adjacent to a degraded groyne G11 [10 May, 2017].

An alternative is rock armour.

The defences configuration at Mappleton, completed in 1991 to protect 447 metres of coast with rock armour, cost approximately £2 million. Per metre of cliff length, that is £4,474 [£10,098, BoE, January 2025], though this includes a cross-beach groyne and sediment holding cell.

A costings exercise in 2014, to extend the Mappleton defences because of concern over the long-term future of the B1242 coastal road, arrived at an estimate of more than £10 million for half a mile or, at the least, £12,427 [£16,852] per metre.

At Easington, a rock revetment of 1,016 metres in length constructed opposite the gas terminal cost £6.6 million in 1999, £6,496 [£12,211] per metre.

Defences at Easington. The artificially profiled bank-like cliff is covered by mesh, and vegetated [12 March, 2014].

Completed in 2020, the Withernsea extension cost £7 million. This was for 400 metres of new rock and 100 metres realignment of existing rock. All told, the 500 metres of work amounted to £14,000 per metre [£17,453].

The above examples, one exercise and three actual cases, provide a guide to the cost per metre of durable coastal protection. To adopt the Easington model, which is a relatively simple design having no cross-beach component, and to apply it to the 51,827 metres of undefended glacially deposited clay coastline, from Sewerby to the Neck of Spurn, would total £632,859,497.

‘no active intervention’

The informal calculation in the following panel serves to illustrate the point that coastal protection is for the greater part significantly more expensive than ‘no active intervention’, or letting nature take its course. Note that the calculation does not allow for the effects of climate change, such as sea level rise.

Along the coastline, the two main types of land use are agricultural, 51.19%, and holiday parks (caravans, chalets), 11.18%. Holiday accommodation can generally be rolled back as the cliff recedes, quite possibly on to land formerly agricultural. Protection of the two types, together 62.37%, would ask £394,714,468 of the total amount.

the broader picture

An irony of East Yorkshire’s coastal erosion is that some of the material removed adds to the beach. The above panel includes figures for length of unprotected coast and average annual rate of cliff recession. By multipling these together, and the result by average cliff height, a volume may be obtained.

51,608 × 1.68 × 14.7 = 1,274,511 cubic metres per year

Total coastal protection would take this volume from the sediment budget. Almost one-third of the material eroded is sand. Without it, beach levels could expect to be lower, resulting in poorer amenity and more wave energy stressing the defences.

Stability of the Spurn Head peninsula, a natural barrier for the Humber Estuary, relies to a degree on a continuous supply of drifted material. If Spurn were to be starved of sediment and subsequently diminish, tidal flow and patterns in the Humber would alter, leading to risk of flooding, loss of habitats, and disturbance of important navigation channels for shipping.

The Spurn peninsula is vulnerable and sensitive to changes.

Also, by cutting off the sediment from East Yorkshire’s cliff erosion, the coastal area of North-East Lincolnshire would be adversely affected in a number of ways.

A calculation of the financial consequences of the aforementioned is not attempted here. Whatever the figure, maybe of some magnitude, it would need to be added to the £632,859,497 already arrived at. To recall Matthews, who should bear the cost?

It might be concluded that the case for total protection against the sea for the glacially deposited coastal margin of the East Riding of Yorkshire is altogether weak, and the deed unlikely to happen. The setting has all the makings of a myth.

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references

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Page prepared by Brian Williams in February 2025.