Formation of Shingle Beaches

What is the composition of the shingle beach along the Sidmouth coastline?

 


The shingle beach is primarily composed of flints and glacial deposits. These coarse sediments accumulate along the shoreline. Specifically, the sediment includes locally derived flint (from Chalk), chert (from Upper Greensand), and pebbles from the Budleigh Salterton Pebble Beds. Additionally, red sand, clay, and gravel from overlying head deposits contribute to the beach material through cliff rock falls. Historically, the River Sid also added sand and gravel.

How far does the continuous shingle beach extend along the Sidmouth coastline?



The shingle beach is largely continuous for at least two miles between Peak Hill in the west and Salcombe Mouth in the east, although it extends beyond these specific points.

What major geological and historical events contributed to the formation of the shingle beach?



 The formation of the shingle beach is a result of several major events and factors. These include the last Ice Age, which significantly impacted the landscape and sea levels. During warmer interglacial periods, rising sea levels inundated lowlands and transported shingle landwards from gravel plains. Following the last major glacial advance and subsequent global melting, sea levels stabilised around 6,000 years ago, leading to the formation of a large continuous beach known as the "Great Beach" or "west Beach" along the Jurassic Coast, which is the precursor to modern beaches.

What natural processes have been primarily responsible for shaping the Sidmouth coastline over the last 6,000 years?


Over the last 6,000 years, the Sidmouth coastline has been predominantly shaped by the forces of wind, waves, and gravity. Wave action is a key factor in beach development and movement, and sediment is transported by longshore drift, generally moving eastwards along the Jurassic Coast.

How did longshore drift influence the formation of the shingle ridge in Sidmouth?


Longshore drift, the movement of sediment along the coastline, significantly contributed to the accumulation of shingle. This regional drift helped form a high, long, gently curved shingle ridge that originally extended from Chit Rocks to East Beach as part of the Great Beach. This ridge grew across the lower Sid valley inlet, causing the river outlet to be pushed eastwards. 

What is the "Great Beach" and when did it form?

 

The "Great Beach" (also referred to as the "west Beach") was a large, continuous beach formed along most of the Jurassic Coast around 6,000 years ago. It developed as sea levels stabilised following the significant rise in sea levels after the last major glacial advance. The modern beaches are considered descendants of this original feature.

How have human activities impacted the natural state and sediment supply of the Sidmouth beach?

 

Human activities have significantly altered the natural state and sediment supply of the beach, particularly since coastal structures were introduced from 1824. Potential natural sediment sources have been removed (e.g., the shingle spit being covered), trapped upstream (e.g., river sediment by weirs), or blocked by headlands/defences. This has led to a considerable diminution of the Main Beach. To compensate, the beach in front of Sidmouth town has been artificially augmented with imported gravel. These human pressures have also degraded and reduced the area of vegetated shingle and immobilised shingle structures.

In summary, how did the shingle beach in Sidmouth primarily originate and what processes have shaped it over time?

In essence, the shingle beach originated from gravel that was transported landwards by rising post-glacial sea levels, leading to the formation of the large "Great Beach" around 6,000 years ago. This feature was subsequently shaped by ongoing natural processes like waves, currents, and the supply of sediment from eroding cliffs and the river. In more recent centuries, human interventions have significantly disrupted these natural processes, resulting in the beach diminishing and requiring artificial replenishment.