Overview
This lecture provides a comprehensive overview of coastal landscapes, focusing on systems, processes, landforms, management strategies, and the impacts of both natural and human activity on coastal environments.
Coastal Systems and Sediment Cells
- Coasts operate as open systems with inputs and outputs of energy and materials.
- Sediment cells are sections of coastline considered closed in terms of sediment movement.
- Dynamic equilibrium in sediment cells occurs when sediment input and output remain balanced.
- Negative feedback restores equilibrium, while positive feedback exaggerates changes.
- Littoral zone is the area affected by wave action, divided into sub-zones (backshore, foreshore, offshore).
Coastal Processes and Landforms
- Erosion includes abrasion, attrition, hydraulic action, corrosion, and cavitation.
- Erosion rates depend on rock type, wave energy, and environmental factors.
- Classic erosional landforms: caves, arches, stacks, stumps, and wave-cut platforms.
- Longshore drift transports sediment; other transport types: traction, saltation, suspension, solution.
- Deposition forms spits, bars, tombolos, offshore bars, and sand dunes.
Weathering, Mass Movement, and Cliff Profiles
- Weathering types: mechanical (freeze-thaw, salt crystallization, wetting/drying), chemical (carbonation, oxidation, solution), biological (plants, animals, seaweed acids).
- Mass movement types include soil creep, solifluction, mudflows, rockfalls, rock slides, and slumps.
- Cliff profiles influenced by rock resistance, structure, and dip relative to the sea.
- Concordant and discordant coastlines create different landforms such as Dalmatian coasts and headlands/bays.
Coastal Vegetation and Succession
- Vegetation stabilizes coastal landforms and reduces erosion.
- Pioneer plants colonize bare sediment, enabling plant succession and salt marsh formation.
- Plant types: halophytes (salt-tolerant) and xerophytes (drought-tolerant).
Waves, Energy, and Sea Level Change
- High-energy coasts: strong waves, mainly erosional, feature rocky headlands.
- Low-energy coasts: gentle waves, mainly depositional, feature beaches.
- Wave type: constructive (depositional) and destructive (erosional).
- Sea level changes: isostatic (localized, post-glacial/tectonic) and eustatic (global, thermal expansion).
Risks to Coastal Environments
- Coastalisation increases flood and erosion risk for communities.
- Storm surges raise sea levels suddenly, especially with loss of protective vegetation like mangroves.
- Global warming may increase storm frequency and intensity, raising risk of environmental refugees.
Coastal Management Strategies
- Hard engineering uses man-made systems (sea walls, groynes) but can shift erosion elsewhere.
- Soft engineering works with natural processes (beach nourishment, dune stabilization).
- Management options: hold the line, managed realignment, advance the line, or do nothing.
- Cost-benefit analysis compares costs of management to expected benefits.
- Integrated Coastal Zone Management (ICZM) and Shoreline Management Plans (SMPs) apply a holistic, sustainable approach.
Key Terms & Definitions
- Dynamic Equilibrium — Balance of sediment input and output in a sediment cell.
- Sediment Cell — Coastal segment where sediment movement is largely contained.
- Longshore Drift — Transport of sediment along the coast by wave action.
- Hard Engineering — Man-made structures to control coastal processes.
- Soft Engineering — Natural or semi-natural strategies to manage coasts.
- Isostatic Change — Local sea-level change due to land movement.
- Eustatic Change — Global sea-level change due to variations in water volume.
Action Items / Next Steps
- Review the basics of coastal erosion and processes in upcoming concise videos.
- Study diagrams of coastal landforms, sediment cells, and management strategies.
- Prepare for exam questions on coastal systems, processes, and management impacts.