Coastal Sediment Supply
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Coastal Sediment Supply
Coastal sediment supply is the transport of sediment to the beach environment by both fluvial and aeolian transport. While aeolian transport plays a role in the overall sedimentary budget for the coastal environment, it is paled in comparison to the fluvial supply which makes up 95% of sediment entering the ocean. When sediment reaches the coast it is then entrained by longshore drift and littoral cells until it is accreted upon the beach or dunes. While it is acknowledged that storm systems are the driver behind coastal erosion. There is a general consensus that human activity, mainly dam and reservoir impoundments on rivers are the cause of indirect human related coastal erosion, along with other local scale effects such as: land use change, irrigation, gravel extraction and river re-alignment. Rate of supply Worldwide, rivers discharge approximately 35x103 km3 of freshwater into the ocean annually. Transported in this freshwater is 15 to 20 x 109 tons of sediment. This se ...
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Sediment
Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand and silt can be carried in suspension in river water and on reaching the sea bed deposited by sedimentation; if buried, they may eventually become sandstone and siltstone (sedimentary rocks) through lithification. Sediments are most often transported by water (fluvial processes), but also wind (aeolian processes) and glaciers. Beach sands and river channel deposits are examples of fluvial transport and deposition, though sediment also often settles out of slow-moving or standing water in lakes and oceans. Desert sand dunes and loess are examples of aeolian transport and deposition. Glacial moraine deposits and till are ice-transported sediments. Classification Sediment can be classified based on its grain size, grain shape, and c ...
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Luan River
The Luan River (, formerly known as ''Lei Shui'', or ''Ru Shui'') is a river in China. River The river flows northwards from its source in the province of Hebei into the province of Inner Mongolia, and then flows southeast back into Hebei to its mouth on the Bohai Sea. The headstream is known as Shandian River. This part of the river flows near the ancient Mongol capital city of Shangdu. Another important settlement in this section is Duolun. From here, the river's course turns to the southeast. Its length is about 600 km. One subsidiary is the Yixun He, which runs through Hebei. During its course, the Luan also passes by the Great Wall. After Chengde, the river is navigable. The largest city along the river's course is Chengde. Impact crater Geological evidence such as the presence of suevite suggests there is an impact crater An impact crater is a circular depression in the surface of a solid astronomical object formed by the hypervelocity impact of a smaller obje ...
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Coastal Erosion
Coastal erosion is the loss or displacement of land, or the long-term removal of sediment and rocks along the coastline due to the action of waves, currents, tides, wind-driven water, waterborne ice, or other impacts of storms. The landward retreat of the shoreline can be measured and described over a temporal scale of tides, seasons, and other short-term cyclic processes. Coastal erosion may be caused by hydraulic action, abrasion, impact and corrosion by wind and water, and other forces, natural or unnatural. On non-rocky coasts, coastal erosion results in rock formations in areas where the coastline contains rock layers or fracture zones with varying resistance to erosion. Softer areas become eroded much faster than harder ones, which typically result in landforms such as tunnels, bridges, columns, and pillars. Over time the coast generally evens out. The softer areas fill up with sediment eroded from hard areas, and rock formations are eroded away. Also erosion commonly ...
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Coastal Development Hazards
A coastal development hazard is something that affects the natural environment by human activities and products. As coasts become more developed, the vulnerability component of the equation increases as there is more value at risk to the hazard. The likelihood component of the equation also increases in terms of there being more value on the coast so a higher chance of hazardous situation occurring. Fundamentally humans create hazards with their presence. In a coastal example, erosion is a process that happens naturally on the Canterbury Bight as a part of the coastal geomorphology of the area and strong long shore currents. This process becomes a hazard when humans interact with that coastal environment by developing it and creating value in that area. A natural hazard is defined as the release of energy or materials that threaten humans or what they value. In a coastal context these hazards vary temporally and spatially from a rare, sudden, massive release of energy and materials s ...
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Landforms
A landform is a natural or anthropogenic land feature on the solid surface of the Earth or other planetary body. Landforms together make up a given terrain, and their arrangement in the landscape is known as topography. Landforms include hills, mountains, canyons, and valleys, as well as shoreline features such as bays, peninsulas, and seas, including submerged features such as mid-ocean ridges, volcanoes, and the great ocean basins. Physical characteristics Landforms are categorized by characteristic physical attributes such as elevation, slope, orientation, stratification, rock exposure and soil type. Gross physical features or landforms include intuitive elements such as berms, mounds, hills, ridges, cliffs, valleys, rivers, peninsulas, volcanoes, and numerous other structural and size-scaled (e.g. ponds vs. lakes, hills vs. mountains) elements including various kinds of inland and oceanic waterbodies and sub-surface features. Mountains, hills, plateaux, and plains are the fo ...
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Coastal Management
Coastal management is defence against flooding and erosion, and techniques that stop erosion to claim lands. Protection against rising sea levels in the 21st century is crucial, as sea level rise accelerates due to climate change. Changes in sea level damage beaches and coastal systems are expected to rise at an increasing rate, causing coastal sediments to be disturbed by tidal energy. Coastal zones occupy less than 15% of the Earth's land area, while they host more than 40% of the world population. Nearly 1.2 billion people live within 100 km of shoreline and 100 m of sea level, with an average density 3 times higher than the global average for population. With three-quarters of the world population expected to reside in the coastal zone by 2025, human activities originating from this small land area will impose heavy pressure on coasts. Coastal zones contain rich resources to produce goods and services and are home to most commercial and industrial activities. Histor ...
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Raised Beach
A raised beach, coastal terrace,Pinter, N (2010): 'Coastal Terraces, Sealevel, and Active Tectonics' (educational exercise), from 2/04/2011/ref> or perched coastline is a relatively flat, horizontal or gently inclined surface of marine origin,Pirazzoli, PA (2005a): 'Marine Terraces', in Schwartz, ML (ed) ''Encyclopedia of Coastal Science.'' Springer, Dordrecht, pp. 632–633 mostly an old abrasion platform which has been lifted out of the sphere of wave activity (sometimes called "tread"). Thus, it lies above or under the current sea level, depending on the time of its formation.Strahler AH; Strahler AN (2005): ''Physische Geographie.'' Ulmer, Stuttgart, 686 p.Leser, H (ed)(2005): ‚''Wörterbuch Allgemeine Geographie.'' Westermann&Deutscher Taschenbuch Verlag, Braunschweig, 1119 p. It is bounded by a steeper ascending slope on the landward side and a steeper descending slope on the seaward side (sometimes called "riser"). Due to its generally flat shape, it is often used for a ...
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Modern Recession Of Beaches
Beach evolution occurs at the shoreline where sea, lake or river water is eroding the land. Beaches exist where sand accumulated from centuries-old, recurrent processes that erode rocky and sedimentary material into sand deposits. River deltas deposit silt from upriver, accreting at the river's outlet to extend lake or ocean shorelines. Catastrophic events such as tsunamis, hurricanes, and storm surges accelerate beach erosion. Accretion and erosion Sudden and rapid processes Tsunamis and hurricane-driven storm surges Tsunamis, potentially enormous waves often caused by earthquakes, have great erosional and sediment-reworking potential. They may strip beaches of sand that may have taken years to accumulate and may destroy trees and other coastal vegetation. Tsunamis are also capable of flooding hundreds of meters inland past the typical high-water level and fast-moving water, associated with the inundating tsunami, can crush homes and other coastal structures. A storm ...
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Beach Nourishment
Beach nourishment (also referred to as beach renourishment, beach replenishment, or sand replenishment) describes a process by which sediment, usually sand, lost through longshore drift or erosion is replaced from other sources. A wider beach can reduce storm damage to coastal structures by dissipating energy across the surf zone, protecting upland structures and infrastructure from storm surges, tsunamis and unusually high tides. Beach nourishment is typically part of a larger integrated coastal zone management aimed at coastal defense. Nourishment is typically a repetitive process since it does not remove the physical forces that cause erosion but simply mitigates their effects. The first nourishment project in the United States was at Coney Island, New York in 1922 and 1923. It is now a common shore protection measure used by public and private entities. History The first nourishment project in the U.S. was constructed at Coney Island, New York in 1922–1923. Before ...
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Beach Evolution
Beach evolution occurs at the shoreline where sea, lake or river water is eroding the land. Beaches exist where sand accumulated from centuries-old, recurrent processes that erode rocky and sedimentary material into sand deposits. River deltas deposit silt from upriver, accreting at the river's outlet to extend lake or ocean shorelines. Catastrophic events such as tsunamis, hurricanes, and storm surges accelerate beach erosion. Accretion and erosion Sudden and rapid processes Tsunamis and hurricane-driven storm surges Tsunamis, potentially enormous waves often caused by earthquakes, have great erosional and sediment-reworking potential. They may strip beaches of sand that may have taken years to accumulate and may destroy trees and other coastal vegetation. Tsunamis are also capable of flooding hundreds of meters inland past the typical high-water level and fast-moving water, associated with the inundating tsunami, can crush homes and other coastal structures. A storm ...
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Beach
A beach is a landform alongside a body of water which consists of loose particles. The particles composing a beach are typically made from rock, such as sand, gravel, shingle, pebbles, etc., or biological sources, such as mollusc shells or coralline algae. Sediments settle in different densities and structures, depending on the local wave action and weather, creating different textures, colors and gradients or layers of material. Though some beaches form on inland freshwater locations such as lakes and rivers, most beaches are in coastal areas where wave or current action deposits and reworks sediments. Erosion and changing of beach geologies happens through natural processes, like wave action and extreme weather events. Where wind conditions are correct, beaches can be backed by coastal dunes which offer protection and regeneration for the beach. However, these natural forces have become more extreme due to climate change, permanently altering beaches at very rapid ...
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Integrated Coastal Zone Management
Integrated coastal zone management (ICZM), integrated coastal management (ICM), or integrated coastal planning is a coastal management process for the management of the coast using an integrated approach, regarding all aspects of the coastal zone, including geographical and political boundaries, in an attempt to achieve sustainability. This concept was born in 1992 during the Earth Summit of Rio de Janeiro. The specifics regarding ICZM is set out in the proceedings of the summit within Agenda 21, ''Chapter 17''. Framework ICZM provides a global common thought process and decision making framework which is flexible enough to find solutions tailored to the diverse range of world's as well as unique national, regional and local coastline and coastal environments and needs. ICZM management must embrace a holistic viewpoint of the functions that makeup the complex and dynamic nature of interactions in the coastal environment. Management framework must be applied to a defined geograph ...
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