Coastal management

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A - groynes.

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At Mappleton on the Holderness coast, two rock groynes were built and rock armour was placed along the foot of the cliff.

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Before 2000 the cliffs at both villages retreated at about 1.5 m a year. After the defences were built at Village A in 2000, its rate of retreat fell sharply to about 0.3 m a year by 2005 and to about 0.1 m a year by 2020. At Village B the opposite happened: the rate increased to about 2.4 m a year by 2005 and about 3.4 m a year by 2020, more than twice the rate before 2000.

The rock armour at Village A absorbs wave energy at the foot of the cliffs, and the groynes trap sediment carried south by longshore drift, building a wider beach that protects the cliffs. Because the sediment is trapped at Village A, less reaches Village B, so its beach becomes narrower and its cliffs are attacked by more powerful waves. This is similar to what happened at Mappleton and Cowden on the Holderness coast.

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At Mappleton on the Holderness coast, two rock groynes and rock armour were built in 1991. The main positive effect was that the village and the B1242 coast road were protected. The groynes trapped sediment moving south by longshore drift, so a wider beach built up in front of Mappleton, absorbing wave energy, and the cliffs there became much more stable.

However, the scheme had negative effects further south. Because the groynes trapped sediment, less reached the beaches south of Mappleton. These beaches became narrower, so the cliffs were exposed to more powerful waves and erosion increased, especially at Cowden, further south, where farmland and some properties were lost.

This caused conflict. People in Mappleton were pleased that their homes and road had been saved, but landowners at Cowden felt that their land had been sacrificed to protect another village, and argued that they should also be protected or compensated. Some people questioned whether it was right to spend about £2 million of public money protecting one small village, while others argued that the coast should be left to erode naturally because the sediment also supplies beaches and Spurn Head further south. The scheme shows how protecting one place can create problems elsewhere along the coast.