Logo South Asian Disaster Knowledge Network
Search:
Site Search Google   GO
Bullet River and Sea Erosion
Home » Hydro Meteorological Disasters » River and Sea Erosion

Factors that influencing the coast are
  • Sand sources and sinks:Beach material can vary in size from very fine sand (0.005 cm) to small pebbles (1.5 cm). Sand is brought to the shore from the continental shelf, rivers and eroding cliffs, sand dunes, as well as from other beaches through the action of long shore currents.
  • Sinks for the sand include continental shelf accumulations of sand that are in water at depths greater than 30 meters (100 feet) and sand that is carried into deep ocean canyons. This sand is below the "reach" of the waves and cannot be moved and returned to the beach. In addition, sand that is blown inland is also lost from the beach.
  • Rising sea levelTo assess the scope of changes in sea level, scientists have developed methods to interpret the geologic record left by prehistoric events.


Other factors that influence sea level include
Sea Erosion
  • Size of polar ice caps and valley glaciers which change the amount of water available for oceans and seas
  • Expansion and contraction of ocean volume due to changes resulting from plate tectonics
  • Rising and sinking of coasts due to plate tectonic changes
  • Warming of ocean water which leads to increased volume for the same amount of water
  • Increase in total water available in the ocean due to human activities which release groundwater and make it part of the surface water system




Some beach erosion factors
  • Effects of human impact, such as construction of artificial structures, mining of beach sand, offshore dredging, or building of dams or rivers.
  • Loss of sediment offshore, onshore, alongshore and by attrition.
  • Reduction in sediment supply due to deceleration cliff erosion.
  • Reduction in sediment supply from the sea floor.
  • Increased storminess in coastal areas or changes in angle of wave approach.
  • Increase in beach saturation due to a higher water table or increased precipitation


Natural Factors Affecting Shoreline Changes and their effects:
Factor Effect Time Scale Comments
Sediment supply (source and sinks) Accretion/Erosion Decades to Millennia Natural supply from inland or shore face and inner shelf sources can contribute to shoreline stability or accretion
Sea Level Rise Erosion Centuries to Millennia Relative sea level rise
Sea Level Change Erosion Months to years Causes poorly understood
Storm surge Erosion Hours to days Very critical to erosion magnitude
Large wave height Erosion Hours to months Individual storms or seasonal effects
Short wave period Erosion Hours to months Individual storms or seasonal effects
Waves of small steepness Accretion Hours to months Summer conditions
Alongshore currents Accretion, no change, or erosion Hours to millennia Discontinuities (up-drift/down-drift) and nodal points
Rip currents Erosion Hours to months Narrow seaward-flowing, near-bottom currents may transport significant quantities of sediment during coastal storms.
Underflow Erosion Hours to days Seaward-flowing, near-bottom currents may transport significant quantities of sediment during coastal storms.
Inlet presence Net erosion; high instability Years to centuries Inlet-adjacent shorelines tend to be unstable because of fluctuations or migrations inlet position; net effect of inlets is erosional owing to sand storage in tidal shoals.
Over wash Erosional Hours to days High tides and waves cause sand transport over barrier beaches
Wind Erosional Hours to centuries Sand blown inland from beach
Subsidence, Compaction Erosion Years to millennia Natural or human-induced withdrawal of subsurface fluids
Subsidence, Tectonic Erosion/Accretion Instantaneous, centuries to millennia Earthquakes; Elevation or subsidence of plates
Weekly Disaster Updates
Software Developed by Tata Consultancy Services Limited. Copyright © 2009 SADKN, All Rights Reserved                     
66
  Concurrent Users:
1142822
Number of hits: