Longshore Drift and Beach Material: Key Factors in Coastal Erosion

The Holderness Coast's vulnerability to erosion is further exacerbated by the nature of its beach material and the process of longshore drift.

Definition: Longshore drift is the movement of beach material along the coast by wave action.

Key points:

1. Beach composition: The coast's geology consists primarily of boulder clay, which erodes to produce clay particles easily transported out to sea.
2. Lack of protective beach: There is insufficient sand accumulation to protect the cliff base at high tide.
3. Sediment transport: The little sand produced is moved southwards by longshore drift, leaving cliffs exposed.

Example: The map shows how longshore drift affects various locations along the coast, including Bridlington, Hornsea, and Withernsea.

Coastal management strategies implemented along the Holderness Coast include:

• Sea walls
• Groynes
• Beach nourishment
• Rock armour

These interventions aim to slow erosion and protect key settlements and infrastructure. However, each method has its own set of advantages and disadvantages, which must be carefully considered in coastal management planning.

Sea Walls: A Robust but Costly Coastal Defense

Sea walls are a prominent feature of coastal management along the Holderness Coast, serving as a physical barrier against wave action and erosion.

Definition: A sea wall is a concrete or rock barrier built at the foot of a cliff or the top of a beach to reflect waves and absorb their impact.

Key characteristics of sea walls:

• Height: Typically 3-5 meters high
• Design: Curved face to reflect waves back into the sea
• Continuity: Must be a continuous feature to prevent flanking erosion
• Drainage: Requires proper drainage to handle water from storm surges

Advantages of sea walls:

1. Effective at stopping sea encroachment
2. Often include a walkway, enhancing public access

Disadvantages:

1. Visually unappealing and block sea views
2. Expensive to build and maintain $approximately £10 million per kilometer$

Example: Withernsea's coastal defenses include a sea wall combined with groynes, rock armour, and beach nourishment.

The Withernsea project:

• Cost: £6.3 million
• Benefits: Slows erosion and protects seasonal jobs
• Drawbacks: Limited sea wall strength due to costs, reduced beach access, restricted views, and increased wave noise

This case study demonstrates the complex trade-offs involved in implementing hard engineering solutions like sea walls along the Holderness Coast.

Groynes: Trapping Sediment to Build Beaches

Groynes are another important coastal management strategy employed along the Holderness Coast, particularly in areas like Hornsea and Mappleton.

Definition: Groynes are timber or rock structures built out to sea from the coast, designed to trap sand and interrupt longshore drift.

Key features of groynes:

• Orientation: Usually built at a 5-10° angle from perpendicular to the coast
• Function: Trap sand to broaden the beach, creating a buffer against incoming waves

Hornsea case study:

• Investment: Over £5.2 million in groyne repair and construction
• Additional measures: Raised sea wall, flood doors, and sand dune planting

Advantages of groynes:

1. Relatively low cost compared to other hard engineering solutions
2. Visually acceptable
3. Can increase beach width, benefiting tourism

Disadvantages:

1. May cause erosion elsewhere by interrupting sediment transport
2. Can be considered unnatural and unattractive

Highlight: The effectiveness of groynes can vary, as demonstrated by the contrasting outcomes in Hornsea and Mappleton.

The use of groynes along the Holderness Coast illustrates the challenges of balancing local protection with broader coastal processes and aesthetics.

Mappleton: A Case Study in Coastal Defense and Its Consequences

The coastal village of Mappleton provides a compelling case study of the complexities involved in coastal management along the Holderness Coast.

Historical context:

• In 1786, Mappleton was 3.5 km from the sea
• By 1988, the sea had reached the village's doorstep, threatening homes and infrastructure

The 1991 coastal defense scheme:

• Implemented to protect the village and the vital coast road
• Utilized a combination of hard engineering techniques

Quote: "There was tremendous pressure from local residents to save the village, though in the end it was the threat to the coast road that won the day."

This case study raises important questions about:

1. The long-term sustainability of coastal defenses
2. The balance between protecting individual communities and managing the entire coastline
3. The role of economic factors in decision-making about coastal protection

The Mappleton example demonstrates how interventions on the Holderness Coast can have both positive and negative consequences, highlighting the need for comprehensive, long-term planning in coastal management.

Rock Armour: A Flexible Approach to Coastal Protection

Rock armour is a widely used coastal defense technique along the Holderness Coast, offering a more flexible alternative to traditional sea walls.

Definition: Rock armour consists of large boulders dumped at the foot of a cliff to force waves to break and absorb their energy.

Key characteristics of rock armour:

• Material: Large, often angular boulders
• Placement: Typically transported by barge and placed at the cliff base
• Design: Not secured to the ground, allowing for movement that absorbs wave energy

Advantages of rock armour:

1. Relatively cheap and easy to maintain $£1,000-4,000 per meter$
2. Can be used for fishing, providing additional benefits
3. Flexible and adaptable to changing conditions

Disadvantages:

1. Can be expensive to import suitable rock
2. May block views and access to the beach
3. Often doesn't match the local geology, impacting landscape aesthetics

Example: Withernsea's rock armour installation, costing £6.3 million, demonstrates the significant investment required for this type of coastal defense.

The use of rock armour along the Holderness Coast illustrates the ongoing challenge of balancing effective coastal protection with environmental and aesthetic concerns. Its implementation in various locations provides valuable insights into the long-term efficacy of this approach in managing coastal erosion.

The Holderness Coast: An Overview of Erosion and Coastal Processes

The Holderness Coast is a prime example of rapid coastal erosion in action. Located on the east coast of the UK, this stretch of coastline faces significant challenges due to its unique geographical and geological characteristics.

Highlight: On average, over 2 metres of the Holderness coastline is lost every year, with 4 km of land and 29 villages lost since Roman times.

Several factors contribute to the coast's vulnerability to erosion:

1. Long fetch: The coast is exposed to winds and waves from the northeast, with a fetch of 500-800 km.
2. Powerful currents: Atlantic currents circulating into the North Sea enhance wave energy.
3. Low-pressure weather systems: Intense storms generate huge waves.
4. Deep sea floor: Waves maintain their energy until they reach the cliff base.

Vocabulary: Fetch refers to the distance over which wind blows across open water, affecting wave size and energy.

These factors combine to create a highly dynamic and erosive coastal environment, making the Holderness Coast a critical area for studying coastal processes and management strategies.