Coastal landforms are shaped by the constant interplay of water, wind, and sediment. Beaches, spits, and tombolos form as waves and currents deposit materials along shorelines. These features are dynamic, constantly evolving as environmental conditions change.
Longshore drift plays a crucial role in shaping coastal landscapes. This process moves sediment parallel to the shore, creating and maintaining features like barrier islands. Coastal dunes form above the high tide line, providing natural protection against storms and flooding.
Top images from around the web for Beach Components and Formation The formation of beach cusps and berms... © Eric Jones cc-by-sa/2.0 :: Geograph Britain and Ireland View original
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components of a sandy marine beach – Physical Geology View original
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Coastal hydrodynamics and sediment transport – Homepage of David Gonzalez-Rodriguez View original
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The formation of beach cusps and berms... © Eric Jones cc-by-sa/2.0 :: Geograph Britain and Ireland View original
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components of a sandy marine beach – Physical Geology View original
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Top images from around the web for Beach Components and Formation The formation of beach cusps and berms... © Eric Jones cc-by-sa/2.0 :: Geograph Britain and Ireland View original
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components of a sandy marine beach – Physical Geology View original
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Coastal hydrodynamics and sediment transport – Homepage of David Gonzalez-Rodriguez View original
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The formation of beach cusps and berms... © Eric Jones cc-by-sa/2.0 :: Geograph Britain and Ireland View original
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components of a sandy marine beach – Physical Geology View original
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Beaches accumulate sediment along the shoreline through wave action and longshore currents
Deposited materials include sand, gravel, and shells
Beach profiles consist of distinct components
Foreshore extends from low tide line to high tide line
Backshore lies above high tide line, only affected by waves during storms
Berm forms a raised platform above normal high tide level
Beach cusps create crescentic patterns along the shoreline
Form due to complex interactions between waves, currents, and sediment transport
Typically spaced at regular intervals (10-100 meters apart)
Spits and Tombolos
Spits extend from the mainland into open water as elongated depositional features
Often form where coastline direction changes
Growth depends on consistent sediment supply and longshore drift
Examples include Spurn Point (England) and Sandy Hook (New Jersey)
Tombolos connect islands to the mainland or other islands with sand or gravel bars
Form when waves refract around islands and deposit sediment in their lee
Size and stability influenced by wave energy, sediment supply, and island-mainland distance
Notable examples include Chesil Beach (England) and Monte Argentario (Italy)
Longshore Drift and Deposition
Mechanics of Longshore Drift
Longshore drift moves sediment parallel to the shoreline
Driven by waves approaching coast at oblique angles and longshore currents
Swash-backwash process contributes to net sediment movement
Waves push sediment up beach at an angle
Gravity pulls sediment back perpendicular to shore
Rate and direction influenced by various factors
Wave energy
Coastal orientation
Sediment characteristics (size, shape, density)
Longshore drift shapes depositional landforms
Crucial for formation and maintenance of spits, bars, and barrier islands
Interruptions to drift patterns affect sediment distribution
Groins or jetties cause accretion on updrift side
Erosion occurs on downdrift side of structures
Contributes to zetaform beach development
Curved planform shape results from gradual changes in sediment transport rates
Essential for coastal management strategies
Informs beach nourishment projects
Guides design of coastal protection structures (seawalls, breakwaters)
Types of Coastal Dunes
Coastal dunes accumulate wind-blown sand above high tide line
Serve as natural barriers against storm surges and coastal flooding
Embryo dunes initiate dune formation
Develop when sand traps around pioneer vegetation or obstacles on upper beach
Examples of pioneer plants include sea rocket (Cakile maritima) and sand couch grass (Elytrigia juncea)
Foredunes form primary dune ridge parallel to shoreline
Sand accumulates around vegetation like marram grass (Ammophila) or sea oats (Uniola paniculata)
Provide first line of defense against coastal erosion and storm impacts
Advanced Dune Systems
Parabolic dunes exhibit U-shaped formation
Form when blowouts occur in established dunes
Arms point upwind, often stabilized by vegetation
Examples found in coastal regions of Australia and New Zealand
Transgressive dune sheets create large, mobile sand masses
Move inland over existing landscapes
Form in areas with high wind energy and abundant sand supply
Extensive examples in the Namib Desert coast and parts of coastal Brazil
Backdunes represent older, more stabilized dunes
Located further inland from foredunes
Support diverse vegetation and ecosystems
Often found in coastal dune systems of the Netherlands and Denmark
Stability of Coastal Features
Natural Factors Affecting Stability
Sediment supply balance critical for long-term maintenance
Equilibrium between erosion and deposition required
Sea-level changes impact coastal landform stability
Rising sea levels potentially increase erosion and landward migration
Wave energy and storm frequency shape depositional landforms
Extreme events (hurricanes, nor'easters) can cause significant changes
Vegetation cover contributes to dune and feature stability
Traps sand and reduces wind erosion
Examples include beach grass (Ammophila breviligulata) and sea grape (Coccoloba uvifera)
Anthropogenic and Climate Influences
Human activities disrupt natural sediment transport processes
Coastal development alters sediment pathways
Sand mining reduces available sediment supply
Feature orientation relative to prevailing winds and waves affects stability
Alignment with dominant forces can enhance or reduce erosion potential
Climate change impacts alter long-term stability of depositional systems
Changes in storm patterns affect wave energy and frequency
Altered precipitation regimes influence sediment supply from rivers
Examples include increased erosion rates in Arctic coastal areas due to permafrost thaw