Coastal Management and Sea Level Change

Coastal Dynamics and Management

Coastal Erosion and Sediment Dynamics
  • Coastal environments are dynamic and subject to change by various factors including weather patterns, storms, and human intervention.
  • Increased storm frequency can lead to erosion of dunes, particularly if there is insufficient recovery time between events.
  • Rising sea levels contribute to accelerated erosion of coastal features such as spits and estuaries that remove sediment faster than it can be replenished.
Human Impact on Coastal Systems
  • Human activities, particularly coastal development, pose significant risks to coastal dynamics and sustainability.
  • Coastal areas are heavily populated, with 50% of the world’s population living within coastal regions, and 73% of cities located near coastlines.
  • Development pressures lead to environmental damage, habitat loss, and pollution, further exacerbating coastal instability.
Coastal Management Strategies
  • Coastal management is imperative to protect homes, businesses, and the environment from erosion and flooding. Here are strategies involved in coastal management:-
    • Hold the line: Maintain current defenses against coastal erosion.
    • Advance the line: Build coastal defenses seaward to protect the land.
    • Managed retreat: Allow natural processes to reclaim areas deemed of low value, often exemplified by projects such as Medmerry.
Economic and Social Considerations in Coastal Management
  • Various analyses, including Cost-Benefit Analysis (CBA), are conducted to determine which areas require protection and to justify the expenditure on coastal defenses.
  • Benefits valued in terms of preserved land, infrastructure, and reduced economic loss.
  • Various houses and methods of infrastructure (design, build, maintenance) hold significant monetary value.
Traditional vs. Modern Management Approaches
  • Traditional Strategies:
    • Involves constructing defenses in short sections along coastlines to reduce overall erosion.
    • Hard engineering methods include sea walls, revetments, gabions, riprap, and breakwaters.
    • Advantages: They are effective at deflecting wave energy, providing long-lasting protection.
    • Disadvantages: They are costly to build and maintain, can be visually unappealing, and may cause erosion in adjacent areas due to sediment deprivation.
  • Soft Engineering:
    • Practices include beach nourishment, dune regeneration, and managed retreat.
    • Advantages: These are more sustainable, aesthetically pleasing, and generally result in less environmental impact.
    • Disadvantages: These methods may require frequent maintenance and may be less effective in the short term.
Sustainable Coastal Management
  • Emphasis on cost-effective strategies that mitigate economic, social, and environmental damage.
  • Shoreline Management Plans (SMP) process focuses on specific sediment cells to devise sustainable measures to manage coastal areas with high ecological and economic value.
  • Management strategies are often designed to be self-contained, minimizing negative effects elsewhere.
Factors Influencing Coastal Changes
  • Various forces affect coastline dynamics, including:-
    • Atmospheric changes (high/low tides, climate change, weather patterns).
    • Geological changes (tectonic activity resulting in land uplift or subsidence).
Eustatic and Isostatic Changes
  • Eustatic Change: Refers to sea level changes due to variations in global water volume or changes in ocean basin shape.
    • Induced by climate change, thermal expansion, and glacial melting.
  • Isostatic Change: Localized rising or falling of land relative to the sea, occurring due to tectonic activity or changes in glacial weight.
    • It often results in long-term land formation and reformation dynamics along coastlines.
  • Submerging Coastlines: Occur when sea level rise (eustatic) or land subsidence (isostatic) causes coastal areas to become inundated.
    • This process often leads to the formation of unique landforms:
    • Rias: Submerged river valleys, typically V-shaped in cross-section, which are wider and deeper towards the sea. They are formed when rising sea levels drown river systems, creating sheltered inlets.
    • Fjords: Submerged glacial troughs, characterized by steep-sided, U-shaped valleys carved by glaciers and later inundated by the sea. They are deep and narrow, often with a sill (shallow entrance) where the glacier met the sea.
    • Dalmatian Coasts: Formed when the sea inundates a landscape of parallel folds of resistant rock and softer rock. The sea floods the valleys, leaving the ridges as lines of islands parallel to the coastline, creating a distinctive pattern.
  • Emerging Coastlines: Occur when land rises relative to sea level (isostatic uplift) or sea levels fall (eustatic drop), exposing new land previously submerged.
    • This process typically results in the formation of specific landforms:
    • Raised Beaches: Former beaches that are now found above the current sea level, often marked by old cliff lines behind them. They contain sand, pebbles, and marine shells, indicating their past association with the sea.
    • Marine Terraces: Broad, flat surfaces or platforms created by wave action at a former sea level, which have since been uplifted. They often occur in a series, each representing a distinct period of uplift or sea level drop.
Climate Change Impacts on Coastal Systems
  • Global temperatures have significantly increased, leading to rising sea levels at an average rate of 12 mm/year and predictions of reaching up to 1 m by 2100 if current trends persist.
  • Increased storm intensity due to changes in ocean and atmospheric patterns further exacerbates coastal erosion risks.
  • Vulnerable coastal land and properties become at risk due to contamination of groundwater sources and greater flood susceptibility.
Historical Context of Sea Level Changes
  • Over the last 10,000 years, sea levels have fluctuated significantly, impacted by glaciation periods, rising temperatures, and human activities since the Industrial Revolution.
  • The last glacial period saw sea levels approximately 130 m lower, indicating dynamic shifts in coastal configurations as temperatures rose and ice melted.
Long-term Predictions
  • Future projections suggest ongoing changes will occur due to the interplay of natural processes and human activities.
  • Coastal features are dynamic and will continue to evolve over varying spatial and temporal scales, reflecting the ongoing nature of climate interactions.
Conclusion
  • Coastal areas are vital yet vulnerable environments influenced by natural and anthropogenic factors. Sustainable management, informed by scientific understanding, is critical to the protection and resilience of these coastlines.