7.2 Coastal processes and landforms
3 min read•july 24, 2024
Coastal processes shape our shorelines through waves, currents, and sediment transport. These dynamic forces sculpt beaches, , and , while also posing challenges like and flooding. Understanding these processes is crucial for managing our coasts effectively.
Human activities have significantly impacted coastal areas, leading to increased erosion, pollution, and . To address these issues, coastal management strategies range from hard engineering solutions like seawalls to softer approaches like beach nourishment and managed retreat.
Coastal Processes
Coastal processes and dynamics
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- Waves
- Wind-generated waves form through wind stress on water surface transferring energy
- Swell waves travel long distances from storm centers maintain energy and shape
- bends waves parallel to shore diffraction spreads wave energy around obstacles reflection bounces waves off barriers
- Wave energy and power determine erosion potential and sediment transport capacity
- Currents
- Longshore currents flow parallel to shore transport sediment along coastline
- Rip currents form narrow seaward-flowing channels dangerous for swimmers
- Tidal currents result from gravitational pull of moon and sun affect coastal processes
- Sediment transport
- Longshore drift moves sediment along coast in zigzag pattern (California coast)
- Cross-shore transport moves sediment perpendicular to shoreline (beach erosion during storms)
- Suspension and bedload transport carry sediment in water column and along seafloor
Factors in coastal erosion
- Erosion factors
- Wave energy and intensity determine rate of erosion and sediment removal
- Storm surge and extreme weather events cause rapid erosion and coastal flooding (Hurricane Katrina)
- Sea-level rise increases and inundation of low-lying areas
- Coastal geology and rock type influence erosion rates (soft sedimentary rocks erode faster)
- Accretion factors
- Sediment supply from rivers and offshore sources builds up coastlines (Mississippi Delta)
- Longshore drift patterns deposit sediment in specific areas forming spits and barriers
- Coastal vegetation and dune formation stabilize sediment and promote accretion
- Human influences
- Coastal development and infrastructure alter natural sediment transport patterns
- mining and dredging reduce available sediment for coastal processes
- Damming of rivers decreases sediment supply to coasts (Colorado River)
Coastal Landforms and Management
Formation of coastal landforms
- Beaches
- Beach profile berm foreshore and offshore zones shaped by wave action and sediment transport
- Beach sediment composition and grain size vary based on source and wave energy
- Beach equilibrium and seasonal changes occur due to variations in wave energy and sediment supply
- Barrier islands
- Formation processes and migration driven by sea-level changes and sediment supply
- Components dunes beach overwash fans and back-barrier lagoon provide diverse habitats
- Importance for coastal protection act as natural buffers against storms and waves (Outer Banks NC)
- Sea cliffs
- Formation through wave erosion and weathering creates steep coastal features
- Types hard rock cliffs resistant to erosion soft rock cliffs more easily eroded
- Cliff retreat processes and rates influenced by rock type wave energy and climate
Human impact on coasts
- Human impacts
- Coastal urbanization and tourism increase pressure on coastal ecosystems and resources
- Pollution and water quality degradation harm marine life and coastal habitats (Gulf of Mexico dead zone)
- Habitat destruction and loss of biodiversity threaten coastal ecosystems (mangrove deforestation)
- Coastal management strategies
- Hard engineering solutions
- Seawalls protect coastline from wave action
- Groynes trap sediment and build up beaches
- Breakwaters reduce wave energy reaching the shore
- Soft engineering solutions
- Beach nourishment adds sand to eroding beaches maintains shoreline position
- Dune restoration enhances natural coastal protection and habitat
- Managed retreat and coastal realignment allow natural coastal processes to occur
- Hard engineering solutions
- Integrated Coastal Zone Management (ICZM)
- Balancing economic social and environmental factors for sustainable coastal development
- Stakeholder engagement and participatory planning ensure diverse interests are considered
- Climate change adaptation
- Flood risk assessment and management identify vulnerable areas and implement protection measures
- Nature-based solutions for coastal protection utilize natural features to enhance resilience (living shorelines)
Key Terms to Review (12)
Barrier islands: Barrier islands are long, narrow landforms that are situated parallel to the mainland coast and are separated from it by a lagoon or other body of water. These islands play a crucial role in coastal processes as they protect the mainland from the full force of ocean waves, storms, and erosion, while also serving as important ecosystems and recreational areas.
Coastal erosion: Coastal erosion is the process by which coastlines are eroded and reshaped by the action of waves, currents, tides, and wind. This natural phenomenon leads to the loss of land along the shoreline and can result in significant impacts on ecosystems, human settlements, and coastal infrastructure. Understanding coastal erosion is crucial for managing coastal environments, preparing for sea level rise, and addressing the dynamics of coastal processes and landforms.
Erosion: Erosion is the process by which soil and rock are worn away and transported from one location to another, primarily by wind, water, or ice. This natural process plays a significant role in shaping landscapes, creating sedimentary deposits, and influencing coastal features, all of which are critical for understanding sedimentary processes and how landforms develop along coastlines.
Habitat loss: Habitat loss refers to the reduction or degradation of natural environments where organisms live, which can lead to declines in biodiversity and ecosystem health. This phenomenon occurs through processes like urban development, agriculture, pollution, and climate change, resulting in fragmented ecosystems that can no longer support the species that rely on them. Understanding habitat loss is crucial for addressing environmental issues, as it connects directly to the health of estuaries and coastal wetlands, responses of marine ecosystems to climate shifts, and the effects of coastal processes and landforms.
Littoral zone: The littoral zone is the coastal region where land meets the ocean, typically extending from the high-water mark to the low-water mark. This area is crucial for a variety of ecological processes, including nutrient cycling and habitat provision for numerous marine and terrestrial organisms. It also plays a significant role in coastal processes such as erosion, sediment transport, and the formation of various landforms.
Mangroves: Mangroves are coastal ecosystems characterized by salt-tolerant trees and shrubs that thrive in intertidal zones, where saltwater from the ocean meets freshwater from rivers. These unique ecosystems provide vital habitats for a variety of marine and terrestrial species, playing a crucial role in coastal protection, water quality improvement, and carbon sequestration.
Salt marshes: Salt marshes are coastal wetlands that are flooded and drained by salt water brought in by the tides. These ecosystems are characterized by the presence of salt-tolerant plants and play a critical role in stabilizing shorelines, filtering pollutants, and providing habitat for a diverse range of wildlife. Their unique conditions contribute to the intricate relationships between land, water, and living organisms, making them essential components of coastal environments.
Sand: Sand is a granular material composed of finely divided rock and mineral particles that ranges in size from 0.0625 mm to 2 mm in diameter. It plays a crucial role in marine sediment types and distribution, as well as in coastal processes and landforms. The size, composition, and distribution of sand can significantly affect marine habitats, shoreline dynamics, and sediment transport mechanisms.
Sea cliffs: Sea cliffs are steep, vertical, or near-vertical rock formations that rise sharply from the coastline into the air. These geological structures are primarily formed by the erosional processes of waves and weathering, which shape coastal landscapes. They often provide habitat for various species and can be visually striking features that showcase the power of coastal processes.
Sedimentation: Sedimentation is the process by which particles settle and accumulate in a particular location, often resulting in the formation of sedimentary layers. This process plays a crucial role in shaping marine environments, influencing the characteristics of continental margins, deep ocean basins, estuaries, and coastal wetlands. Understanding sedimentation helps us grasp how these areas evolve over time and how they impact ecosystems and human activities.
Silt: Silt is a fine-grained sediment that is smaller than sand but larger than clay, typically ranging from 0.002 to 0.05 millimeters in diameter. It plays a significant role in shaping marine environments and coastal landscapes due to its ability to retain water and nutrients, making it essential for various marine ecosystems. Its distribution and characteristics can influence sediment transport processes, sedimentation patterns, and the formation of coastal landforms.
Wave refraction: Wave refraction is the bending of ocean waves as they approach the shore, caused by variations in wave speed due to changes in water depth. This phenomenon occurs because waves travel faster in deeper water and slow down as they enter shallower areas, leading to changes in their direction and shape. Understanding wave refraction is crucial for analyzing coastal processes, the formation of landforms, and the behavior of wind-generated waves and swells.