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Groynes Park, New Zealand
A groyne (in the U.S. groin) is a rigid hydraulic structure built perpendicularly from an ocean shore (in coastal engineering) or a river bank, interrupting water flow and limiting the movement of sediment. It is usually made out of wood, concrete, or stone. In the ocean, groynes create beaches, prevent beach erosion caused by longshore drift where this is the dominant process and facilitate beach nourishment. There is also often cross-shore movement which if longer than the groyne will limit its effectiveness. In a river, groynes slow down the process of erosion and prevent ice-jamming, which in turn aids navigation. Groynes run generally perpendicular to the shore, extending from the upper foreshore or beach into the water. All of a groyne may be underwater, in which case it is a ''submerged groyne''. They are often used in tandem with seawalls and other coastal engineering features. Groynes, however, may cause a shoreline to be perceived as unnatural. Groynes are generall ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thomas Digges
Thomas Digges (; c. 1546 – 24 August 1595) was an English mathematician and astronomer. He was the first to expound the Copernican system in English but discarded the notion of a fixed shell of immoveable stars to postulate infinitely many stars at varying distances. He was also first to postulate the " dark night sky paradox". Life Thomas Digges, born about 1546, was the son of Leonard Digges (c. 1515 – c. 1559), the mathematician and surveyor, and Bridget Wilford, the daughter of Thomas Wilford, esquire, of Hartridge in Cranbrook, Kent, by his first wife, Elizabeth Culpeper, the daughter of Walter Culpeper, esquire. Digges had two brothers, James and Daniel, and three sisters, Mary, who married a man with the surname of Barber; Anne, who married William Digges; and Sarah, whose first husband was surnamed Martin, and whose second husband was John Weston. After the death of his father, Digges grew up under the guardianship of John Dee, a typical Renaissance natural philo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
River Morphology
The terms river morphology and its synonym stream morphology are used to describe the shapes of river channels and how they change in shape and direction over time. The morphology of a river channel is a function of a number of processes and environmental conditions, including the composition and erodibility of the bed and banks (e.g., sand, clay, bedrock); erosion comes from the power and consistency of the current, and can effect the formation of the river's path. Also, vegetation and the rate of plant growth; the availability of sediment; the size and composition of the sediment moving through the channel; the rate of sediment transport through the channel and the rate of deposition on the floodplain, banks, bars, and bed; and regional aggradation or degradation due to subsidence or uplift. River morphology can also be affected by human interaction, which is a way the river responds to a new factor in how the river can change its course. An example of human induced change in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Meanders
A meander is one of a series of regular sinuous curves in the channel of a river or other watercourse. It is produced as a watercourse erodes the sediments of an outer, concave bank ( cut bank) and deposits sediments on an inner, convex bank which is typically a point bar. The result of this coupled erosion and sedimentation is the formation of a sinuous course as the channel migrates back and forth across the axis of a floodplain. The zone within which a meandering stream periodically shifts its channel is known as a meander belt. It typically ranges from 15 to 18 times the width of the channel. Over time, meanders migrate downstream, sometimes in such a short time as to create civil engineering challenges for local municipalities attempting to maintain stable roads and bridges.Neuendorf, K.K.E., J.P. Mehl Jr., and J.A. Jackson, J.A., eds. (2005) ''Glossary of Geology'' (5th ed.). Alexandria, Virginia, American Geological Institute. 779 pp. Charlton, R., 2007. ''Fundamentals ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wing Dam
A wing dam or wing dike is a man made barrier that, unlike a conventional dam, only extends partway into a river. These structures force water into a fast-moving center channel which reduces the rate of sediment accumulation, while slowing water flow near the riverbanks. The Mississippi River in North America has thousands of wing dams which were originally constructed to reduce the amount of dredging required when the main navigation channel was maintained to at least . Since that time, additional conventional dams have been built to increase the water level in the river, doubling the depth of the navigation channel to . The wing dams still serve their purpose, but to a lesser extent than before. While wing dams assist in assuring that rivers are navigable, they can also pose a threat to boaters. Many wing dams are often underwater and may be difficult to see, and can easily be struck by vessels. On the other hand, fishermen intentionally fish the quieter waters downstream of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Groyne At Mundesley, Norfolk
A groyne (in the U.S. groin) is a rigid hydraulic structure built perpendicularly from an ocean shore (in coastal engineering) or a river bank, interrupting water flow and limiting the movement of sediment. It is usually made out of wood, concrete, or stone. In the ocean, groynes create beaches, prevent beach erosion caused by longshore drift where this is the dominant process and facilitate beach nourishment. There is also often cross-shore movement which if longer than the groyne will limit its effectiveness. In a river, groynes slow down the process of erosion and prevent ice-jamming, which in turn aids navigation. Groynes run generally perpendicular to the shore, extending from the upper foreshore or beach into the water. All of a groyne may be underwater, in which case it is a ''submerged groyne''. They are often used in tandem with seawalls and other coastal engineering features. Groynes, however, may cause a shoreline to be perceived as unnatural. Groynes are generally s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Headland
A headland, also known as a head, is a coastal landform, a point of land usually high and often with a sheer drop, that extends into a body of water. It is a type of promontory. A headland of considerable size often is called a cape.Whittow, John (1984). ''Dictionary of Physical Geography''. London: Penguin, 1984, pp. 80, 246. . Headlands are characterised by high, breaking waves, rocky shores, intense erosion, and steep sea cliff. Headlands and bays are often found on the same coastline. A bay is flanked by land on three sides, whereas a headland is flanked by water on three sides. Headlands and bays form on discordant coastlines, where bands of rock of alternating resistance run perpendicular to the coast. Bays form when weak (less resistant) rocks (such as sands and clays) are eroded, leaving bands of stronger (more resistant) rocks (such as chalk, limestone, and granite) forming a headland, or peninsula. Through the deposition of sediment within the bay and the erosion ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Barrier Island
Barrier islands are coastal landforms and a type of dune system that are exceptionally flat or lumpy areas of sand that form by wave and tidal action parallel to the mainland coast. They usually occur in chains, consisting of anything from a few islands to more than a dozen. They are subject to change during storms and other action, but absorb energy and protect the coastlines and create areas of protected waters where wetlands may flourish. A barrier chain may extend uninterrupted for over a hundred kilometers, excepting the tidal inlets that separate the islands, the longest and widest being Padre Island of Texas, United States. Sometimes an important inlet may close permanently, transforming an island into a peninsula, thus creating a barrier peninsula, often including a beach, barrier beach. The length and width of barriers and overall morphology of barrier coasts are related to parameters including tidal range, wave energy, sediment supply, sea-level trends, an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Breakwater (structure)
A breakwater is a permanent structure constructed at a coastal area to protect against tides, currents, waves, and storm surges. Part of a coastal management system, breakwaters are installed to minimize erosion, and to protect anchorages, helping isolate vessels within them from marine hazards such as prop washes and wind-driven waves. A breakwater, also known in some contexts as a jetty, may be connected to land or freestanding, and may contain a walkway or road for vehicle access. On beaches where longshore drift threatens the erosion of beach material, smaller structures on the beach, usually perpendicular to the water's edge, may be installed. Their action on waves and current is intended to slow the longshore drift and discourage mobilisation of beach material. In this usage they are more usually referred to as groynes. Purposes Breakwaters reduce the intensity of wave action in inshore waters and thereby provide safe harbourage. Breakwaters may also be small structu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sediment Transport
Sediment transport is the movement of solid particles (sediment), typically due to a combination of gravity acting on the sediment, and/or the movement of the fluid in which the sediment is entrained. Sediment transport occurs in natural systems where the particles are clastic rocks (sand, gravel, boulders, etc.), mud, or clay; the fluid is air, water, or ice; and the force of gravity acts to move the particles along the sloping surface on which they are resting. Sediment transport due to fluid motion occurs in rivers, oceans, lakes, seas, and other bodies of water due to currents and tides. Transport is also caused by glaciers as they flow, and on terrestrial surfaces under the influence of wind. Sediment transport due only to gravity can occur on sloping surfaces in general, including hillslopes, scarps, cliffs, and the continental shelf—continental slope boundary. Sediment transport is important in the fields of sedimentary geology, geomorphology, civil engineering, hy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
