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Hapua
A hapua is a river-mouth lagoon on a mixed sand and gravel (MSG) beach, formed at the river-coast interface where a typically braided, although sometimes meandering, river interacts with a coastal environment that is significantly affected by longshore drift. The lagoons which form on the MSG coastlines are common on the east coast of the South Island of New Zealand and have long been referred to as by the Māori. This classification differentiates hapua from similar lagoons located on the New Zealand coast termed waituna. Hapua are often located on paraglacial coastal areas where there is a low level of coastal development and minimal population density. Hapua form as the river carves out an elongated coast-parallel area, blocked from the sea by a MSG barrier which constantly alters its shape and volume due to longshore drift. Longshore drift continually extends the barrier behind which the hapua forms by transporting sediment along the coast. Hapua are defined as a narrow shor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Waituna
A waituna is a freshwater coastal lagoon on a mixed sand and gravel (MSG) beach, formed where a braided river meets a coastline affected by longshore drift. This type of waterbody is neither a true lake, lagoon nor estuary. This classification differentiates it from hapua, a type of river mouth lagoon. Both waituna and hapua are rare globally but common in New Zealand, where they are considered ecologically significant as sites of traditional Māori people, Maori food-gathering as well as for their diversity of fish and bird species. Waitnua form an interlinked chain of habitats which run the length of the east coast of the South Island: from Wairua Lagoon and Lake Grassmere in Marlborough District, Marlborough, through Lake Ellesmere, Te Waihore / Lake Ellesmere and Coopers Lagoon / Muriwai, Coopers Lagoon in central Canterbury Region, Canterbury, and Washdyke Lagoon and Wainono Lagoon in South Canterbury, to Waituna Lagoon in Southland District, Southland. Waituna Lagoon is one ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rakaia River Mouth, NZ
Rakaia is a town seated close to the southern banks of the Rakaia River on the Canterbury Plains in New Zealand's South Island, approximately 57 km south of Christchurch on State Highway 1 and the Main South Line. Immediately north of the township are New Zealand's longest road bridge and longest rail bridge, both of which cross the wide shingle beds of the braided river at this point. Both bridges are approximately 1750 metres in length. Rakaia was also the junction of the Methven Branch, a branch line railway to Methven that operated from 1880 until its closure in 1976. An accident at the railway station in 1899 killed four people. Rakaia's most obvious feature is a large fibreglass salmon. The river from which the town takes its name is known for its salmon fishing and jetboating. The town and river were previously known as ''Cholmondeley'', but the Maori name would eventually prevail over the English one. The rural community of Acton is located south of the Rakaia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fluvial
In geography and geology, fluvial processes are associated with rivers and streams and the deposits and landforms created by them. When the stream or rivers are associated with glaciers, ice sheets, or ice caps, the term glaciofluvial or fluvioglacial is used. Fluvial processes Fluvial processes include the motion of sediment and erosion or deposition on the river bed. The movement of water across the stream bed exerts a shear stress directly onto the bed. If the cohesive strength of the substrate is lower than the shear exerted, or the bed is composed of loose sediment which can be mobilized by such stresses, then the bed will be lowered purely by clearwater flow. In addition, if the river carries significant quantities of sediment, this material can act as tools to enhance wear of the bed ( abrasion). At the same time the fragments themselves are ground down, becoming smaller and more rounded (attrition). Sediment in rivers is transported as either bedload (the coarser fr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Southern Alps
The Southern Alps (; officially Southern Alps / Kā Tiritiri o te Moana) is a mountain range extending along much of the length of New Zealand's South Island, reaching its greatest elevations near the range's western side. The name "Southern Alps" generally refers to the entire range, although separate names are given to many of the smaller ranges that form part of it. The range includes the South Island's Main Divide, which separates the water catchments of the more heavily populated eastern side of the island from those on the west coast. Politically, the Main Divide forms the boundary between the Marlborough, Canterbury and Otago regions to the southeast and the Tasman and West Coast regions to the northwest. Names The Māori name of the range is , meaning "the Mirage of the Ocean". The English explorer James Cook bestowed the name ''Southern Alps'' on 23 March 1770, admiring their "prodigious height". p. 384. They had previously been noted by Abel Tasman in 1642, whose ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Swash
Swash, or forewash in geography, is a turbulent layer of water that washes up on the beach after an incoming wave has broken. The swash action can move beach materials up and down the beach, which results in the cross-shore sediment exchange. The time-scale of swash motion varies from seconds to minutes depending on the type of beach (see Figure 1 for beach types). Greater swash generally occurs on flatter beaches. The swash motion plays the primary role in the formation of morphological features and their changes in the swash zone. The swash action also plays an important role as one of the instantaneous processes in wider coastal morphodynamics. There are two approaches that describe swash motions: (1) swash resulting from the collapse of high-frequency bores (''f''>0.05 Hz) on the beachface; and (2) swash characterised by standing, low-frequency (''f''20 indicate dissipative conditions where swash is characterised by standing long-wave motion. Values εb<2.5 indicate r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Canterbury Bight
The Canterbury Bight is a large bight on the eastern side of New Zealand's South Island. The bight runs for approximately from the southern end of Banks Peninsula to the settlement of Timaru and faces southeast, exposing it to high-energy storm waves originating in the Pacific Ocean. The bight is known for rough conditions as a result, with wave heights of over common. Much of the bight's geography is shaped by this high-energy environment interacting with multiple large rivers which enter the Pacific in the bight, such as the Rakaia, Ashburton / Hakatere, and Rangitata Rivers. Sediment from these rivers, predominantly Greywacke, is deposited along the coast and extends up to out to sea from the current shoreline. Multiple '' hapua'', or river-mouth lagoons, can be found along the length of the bight where waves have deposited sufficient sediment to form a barrier across a river mouth, including most notably Lake Ellesmere / Te Waihora and Washdyke Lagoon Zones of the Canterbur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hurunui River
The Hurunui River is the fourth largest of the four principal rivers in north Canterbury, New Zealand, with a catchment area of . The river flows from the eastern side of the Southern Alps, to the Pacific Ocean. Geography The head of the Hurunui River is at Harper Pass; on the other side of the pass is the Taramakau River. Some of the tributaries include the Jollie Brook, the Hurunui River South Branch, the Glenrae River and the Mandamus River. The Hurunui River flows through Lake Sumner. A hot pool has been constructed at the base of a small waterfall on a side stream of the river. Recreation The river has rapids rated class II and III on the international scale of river difficulty and is popular for kayaking. The best whitewater is considered to be below the confluence of the north and south branches of the river in Maori Gully and in the Harwarden Gorge. Chinook salmon (''Oncorhynchus tshawytscha'') were introduced from California in the 1900s for game fishing. Water co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ashburton River / Hakatere
The Ashburton River / Hakatere is a river in the Canterbury region of New Zealand, flowing across Mid Canterbury from the Southern Alps to the Pacific Ocean. The official name of the river was amended to become a dual name by the Ngāi Tahu Claims Settlement Act 1998. It has been identified as an Important Bird Area by BirdLife International because it supports breeding colonies of the endangered black-billed gull. Description The river has two branches which meet from the coast, just inland of the town of Ashburton. The branches remain parallel and no more than apart for a further upstream of their confluence, finally diverging near the small settlement of Ashburton Forks.New Zealand 1:50000 Topographic Map seriesheet BX20Methven The rivers' path southeast across the Canterbury Plains lies in a shallow depression between the higher shingle fans created by the much larger Rakaia and Rangitata rivers. Both branches are crossed via siphons by the Rangitata Diversion Race, part ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rakaia River
The Rakaia River is in the Canterbury Plains in New Zealand's South Island. The Rakaia River is one of the largest braided rivers in New Zealand. The Rakaia River has a mean flow of and a mean annual seven-day low flow of . In the 1850s, European settlers named it the ''Cholmondeley River'', but this name lapsed into disuse. Description It rises in the Southern Alps, travelling in a generally easterly or southeasterly direction before entering the Pacific Ocean south of Christchurch. It forms a hapua as it reaches the ocean. For much of its journey, the river is braided river, braided, running through a wide shingle bed. Close to Mount Hutt, however, it is briefly confined to a narrow canyon known as the Rakaia Gorge. The Rakaia River is bridged in two places. The busiest crossing is at the small town of Rakaia, from the river mouth, where State Highway 1 (New Zealand), State Highway 1 using Rakaia Bridge and the South Island Main Trunk Railway cross the river using sepa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Marine Geology
Marine geology or geological oceanography is the study of the history and structure of the ocean floor. It involves geophysical, geochemical, sedimentological and paleontological investigations of the ocean floor and coastal zone. Marine geology has strong ties to geophysics and to physical oceanography. Marine geological studies were of extreme importance in providing the critical evidence for sea floor spreading and plate tectonics in the years following World War II. The deep ocean floor is the last essentially unexplored frontier and detailed mapping in support of both military (submarine) objectives and economic (petroleum and metal mining) objectives drives the research. Overview The Ring of Fire around the Pacific Ocean with its attendant intense volcanism and seismic activity poses a major threat for disastrous earthquakes, tsunamis and volcanic eruptions. Any ''early warning'' systems for these disastrous events will require a more detailed understanding of marine ge ... [...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, h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
