The Exuma Cays Beach Erosion Decision
A 3 km stretch of beach on a small Exuma cay has narrowed from about 25 m to 8 m in ten years. Behind the beach are 14 houses, a small hotel with 20 rooms and a road. The cay is low, with its highest point about 4 m above sea level, and it faces the open Atlantic. The beach is fed by sand moved along the shore by waves and currents, and by sand from a coral reef offshore. Recent years have seen stronger storms and a rise in sea level. The community must choose between a rock seawall along the whole frontage, beach nourishment with imported sand, or moving the houses back and replanting the dunes. Each option has a cost and a risk.
1. Explain why the beach has narrowed, using the processes that move sand along this coast.
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The beach is a sediment budget: sand arrives from the reef and from longshore drift, and sand leaves when waves and currents carry it away. Several things have changed at once. Stronger storms remove more sand in each event than normal waves can replace. Sea-level rise means waves break further inland, so the beach rolls back and the dune is cut away. If the reef is damaged or bleached, it produces less new sand and absorbs less wave energy, so waves reach the shore with more force. Building close to the dune stops the beach from moving inland, so it is squeezed between the sea and the houses. The narrowing from 25 m to 8 m is a loss of 17 m in ten years, about 1.7 m a year, which is fast and suggests the budget is in deficit rather than simply shifting.
2. Compare the seawall and the beach nourishment options, and recommend one.
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A seawall protects the houses immediately and is simple to build, but it reflects wave energy, so the beach in front is scoured and the sand is lost faster; in time the houses sit behind a wall with no beach, which destroys the hotel's main attraction. It also costs a lot for 3 km and must be maintained. Beach nourishment replaces the lost sand and keeps a beach for residents and the hotel, but imported sand is expensive, may not match the local sand, and will wash away within a few years unless the cause of loss is addressed; it also needs repeating. A judgement should weigh the hotel's dependence on the beach against the cost. The best answer recommends nourishment combined with dune replanting and a setback rule for new building, because the beach is the economic asset, and rejects a continuous seawall as self-defeating. It should note that nourishment is only sustainable if the reef is protected.
3. The hotel owner says moving houses back is 'giving up'. Evaluate this view.
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Moving back looks like defeat but is often the cheapest long-term choice. The cay is only about 4 m high, so a wall or a nourished beach must be maintained forever against rising seas, and each repair costs money the community may not have. A managed retreat moves the 14 houses and the road inland, replants the dune with native grasses, and lets the beach widen naturally. It protects the beach, which is the hotel's real asset, and avoids the scour caused by a wall. The costs are real: moving houses is disruptive, some land may be unavailable, and the hotel loses its front-row position. The judgement should be that retreat is not giving up but choosing which asset to protect; it is most sensible where there is land to move to, and least sensible where there is not. A mixed approach, retreat for the houses and nourishment for the hotel frontage, may be fairest.