The Changing Shoreline

3: Sidmouth’s Changing Coastline: Erosion, Risks & Management

Explore the future of Sidmouth’s cliffs and beaches. Learn about the 2m/year erosion rate , the risks of "coastal squeeze" , and how the Beach Management Plan aims to protect the town.

Sidmouth’s coastline is currently at a crossroads. The same natural forces that created the "Great Beach" now pose significant risks to the town’s residents and infrastructure. Understanding how we manage this shifting landscape is key to the town’s survival.

1. The Reality of Coastal Erosion

The soft sandstone cliffs of Sidmouth have been eroding for millions of years, but the pace is accelerating.

Higher Erosion Rates: Recent research suggests an erosion rate of at least two metres per year—significantly higher than older estimates.
Property at Risk: It is estimated that heavy erosion could claim clifftop homes within the next 20 years.
Frequent Cliff Falls: Major collapse events occur frequently along this stretch of the coast.

2. The Vulnerability of the Town Centre

Because the town sits in a low-lying valley, it faces a unique set of threats:

Shrinking Main Beach: Over recent decades, the beach has grown smaller, providing less of a "buffer" for the sea wall.
Wave Overtopping: When beach levels are low, storms can throw large volumes of water across the Esplanade and into the town centre.
Historical Scouring: In the late 1980s and early 90s, storms scoured the beach so severely that old groynes were exposed and the sea wall was left with almost no protection.

3. The Unintended Consequences of Engineering

Human efforts to "hold the line" often have a ripple effect on the rest of the coast:

The Rock Islands: Built at the end of the 20th century, these offshore islands have been linked to increased erosion on the East Beach and its cliffs.
Coastal Squeeze: When we build hard defenses (like sea walls), coastal habitats get trapped. They are eroded from the sea side but cannot move inland, a process known as coastal squeeze.
Reduced Sediment: Engineering works designed to stabilise one area often reduce the natural flow of sediment to other parts of the coast.

4. The Path Forward: The Beach Management Plan

Managing the coast is a complex "tug-of-war" between engineering and nature. The current strategy for Sidmouth includes:

Beach Nourishment: Importing new shingle onto both East Beach and the Main Beach to maintain a healthy "buffer".
New Infrastructure: Installing a new groyne on East Beach to help trap sediment.
The Splash Wall: Raising the promenade's splash wall by up to one metre to prevent flooding during storms.

Before you go

The "Hold the Line" Field Investigation

This activity encourages learners to act as "Coastal Managers" by observing the real-world effects of erosion and the defences currently in place at Sidmouth.

Part 1: The Erosion Audit (East Beach)

Goal: Observe the power of natural processes and the speed of geological change.

Locate a Cliff Fall: Walk toward East Beach (from a safe distance) to identify areas where the cliffs have recently collapsed.
The 20-Year Marker: Since research suggests clifftop homes could be claimed within 20 years due to an erosion rate of 2 meters per year, look up and visually estimate where the cliff edge might be in two decades.
Sediment Search: Identify the different materials at the base of the cliff. Can you find the flint and chert that dominate this section?.

Part 2: The Engineering Inspection (The Esplanade)

Goal: Understand how the town is protected and where those defenses are failing.

The Sea Wall Check: Examine the sea wall along the Main Beach. Look for signs of "overtopping"—areas where sand or debris have been thrown onto the walkway by waves.
The Beach Buffer: Compare the height of the shingle beach to the sea wall. Is the beach high enough to act as a "buffer," or is the wall exposed to direct wave impact?.
The Splash Wall Challenge: Locate the promenade splash wall. The current Beach Management Plan proposes raising this by up to one metre. How a higher wall would change the view versus how it would protect the town from flooding.

Part 3: The "Unintended Consequences" Discussion

Goal: Critical thinking about "Coastal Squeeze" and engineering.

The Rock Islands: Look out at the rock islands built at the end of the 20th century.
Discussion Point: If these islands protect the town but lead to increased erosion on East Beach, was it a fair trade-off?.
Coastal Squeeze Observation: Look for areas where the beach is trapped between the rising sea and a concrete wall. If the beach cannot move inland, what happens to the habitat?.

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