Eastmere Spit: Sediment Budget and Coastal Management Choices
The shingle spit of Eastmere stretches 14 km south from a holiday resort. Longshore drift moves sediment north to south. In 1998, a groyne field was built at the resort updrift; since then the beach at Eastmere village has lowered by about 1.8 m, 22 properties have been lost, and the coast road is within 15 m of the cliff edge. Sea level is rising at 4 mm per year. Cliff sediment supply has fallen because sea walls protect the updrift resort. The council has £5 million for 10 years. Options include extending the groynes, beach nourishment of 60,000 m³ every five years at £1.2 million per operation, managed realignment of 40 ha of farmland, or doing nothing. Eighteen more properties are at risk. The farmland owner opposes realignment, while conservation groups argue that realignment would create valuable saltmarsh.
1. Recommend a coastal management strategy, justifying it with reference to the sediment budget and cost-benefit.
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The sediment budget is negative downdrift because the groyne field traps northward-moving shingle and sea walls cut cliff supply. Extending the groynes would worsen the deficit at Eastmere. Nourishment of 60,000 m³ every five years at £1.2 million costs £2.4 million over ten years, within the £5 million budget, and directly replaces lost sediment; it buys time for 18 properties and the road. Managed realignment of 40 ha farmland is cheaper and creates saltmarsh, which dissipates wave energy, but it does not protect the village unless coupled with a setback. A defensible mix is nourishment for the village frontage and realignment for the southern farmland, where property value is lower. Doing nothing is not defensible for the village but may be rational for the farmland if compensation is agreed. This mix respects sediment processes and cost-benefit.
2. Explain the processes linking the updrift groynes to erosion at Eastmere.
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Groynes are impermeable barriers across the littoral zone. They interrupt longshore drift, trapping sediment on the updrift side and starving the downdrift coast. At Eastmere, the groyne field at the resort holds shingle that would otherwise move south. The result is a narrower, lower beach downdrift, less wave dissipation, and increased cliff and property erosion. Sea walls updrift add to the deficit by preventing cliff erosion from replenishing the beach. The 1.8 m beach lowering and loss of 22 properties are consistent with this human-induced sediment deficit, not just sea-level rise.
3. Assess whether a ‘do nothing’ approach could ever be justified for part of this coast.
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Do nothing may be rational for the 40 ha farmland if the cost of defence exceeds the land value and if realignment creates compensatory saltmarsh. It is not rational for the village frontage because 18 properties and the coast road have high social and economic value. The judgement depends on who bears the cost: defending everywhere locks the council into unsustainable spending, while abandoning the village raises equity concerns. A planned retreat from low-value farmland combined with nourishment of the village is more defensible than uniform do nothing. ‘Do nothing’ should therefore be selective and compensated, not a blanket policy.