11.3 Sediment Transport and Coastal Processes

Coastal sediment transport shapes shorelines through the movement of particles by waves, currents, and tides. Understanding these processes is crucial for managing coastal areas and predicting how they'll change over time. It's all about the dance between water and land.

Environmental impact assessments must consider how coastal projects affect sediment transport. Changes in sediment flow can lead to erosion, alter habitats, and impact infrastructure. It's a delicate balance that requires careful study and planning.

Coastal Sediment Transport

Sediment Movement and Deposition

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• Sediment dynamics involve the movement, deposition, and erosion of sediment particles along the coast
  • Influenced by factors such as waves, currents, and tides
  • Sediment size and composition affect transport patterns (sand, silt, clay)
• Littoral drift refers to the longshore transport of sediment parallel to the shoreline
  • Driven by wave action and currents
  • Contributes to the formation and evolution of coastal features (spits, barrier islands)
• Scour is the localized erosion of sediment caused by turbulent water flow
  • Often occurs around structures like piers, jetties, and foundations
  • Can undermine the stability of coastal infrastructure (bridges, seawalls)

Seabed Changes and Monitoring

• Bathymetry changes refer to alterations in the underwater topography of the seabed
  • Influenced by sediment transport processes and human activities
  • Monitoring bathymetry is crucial for navigation, coastal management, and engineering projects
• Techniques for measuring bathymetry include echo sounding, side-scan sonar, and LiDAR
  • Provides detailed maps of water depths and seabed features (channels, shoals, reefs)
• Bathymetric surveys help assess the impact of coastal structures on sediment transport and seabed morphology
  • Identifies areas of accretion or erosion
  • Informs the design and placement of coastal protection measures (breakwaters, groins)

Shoreline Impacts

Erosion and Morphological Changes

• Coastal erosion is the loss of land along the shoreline due to the action of waves, currents, and tides
  • Can be exacerbated by human activities (coastal development, sand mining)
  • Threatens coastal habitats, infrastructure, and communities
• Shoreline morphology refers to the shape and features of the coastline
  • Influenced by factors such as sediment supply, wave energy, and sea level
  • Includes landforms like beaches, cliffs, estuaries, and deltas
• Coastal structures and interventions can alter shoreline morphology
  • Groins and jetties can trap sediment and create localized accretion
  • Seawalls and revetments can reflect wave energy and cause downdrift erosion

Wave and Tidal Interactions

• Wave attenuation is the reduction in wave height and energy as waves propagate towards the shore
  • Influenced by factors such as water depth, bottom friction, and vegetation
  • Coastal ecosystems like coral reefs and seagrass beds can dissipate wave energy and protect shorelines
• Tidal flow alteration refers to changes in the speed, direction, and patterns of tidal currents
  • Can be caused by coastal structures, dredging, or land reclamation
  • Affects sediment transport, water quality, and ecological processes (nutrient exchange, larval dispersal)
• Understanding the interactions between waves, tides, and coastal morphology is crucial for effective shoreline management
  • Informs the design of coastal protection measures and ecosystem restoration projects
  • Helps assess the potential impacts of coastal development and climate change (sea level rise, storm surges)