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23-591: The Waipawa River is a braided river of southern Hawke's Bay , in New Zealand 's eastern North Island . It flows southeast from the slopes of 1,687 m (5,535 ft) Te Atuaoparapara (once known as 'Sixty-six') in the Ruahine Range , past the town of Waipawa , before joining the Tukituki River . The river rises at the 1,326 m (4,350 ft) Waipawa Saddle, which is also the source of

46-406: A meandering river , which has a single sinuous channel. It is also distinct from an anastomosing river , which consist of multiple interweaving semi-permanent channels which are separated by floodplain rather than channel bars; these channels may themselves be braided. The physical processes that determine whether a river will be braided or meandering are not fully understood. However, there

69-542: A meandering profile. A stream with cohesive banks that are resistant to erosion will form narrow, deep, meandering channels, whereas a stream with highly erodible banks will form wide, shallow channels, preventing the helical flow of the water necessary for meandering and resulting in the formation of braided channels. Braided rivers occur in many environments, but are most common in wide valleys associated with mountainous regions or their piedmonts or in areas of coarse-grained sediments and limited growth of vegetation near

92-407: A trench or ditch . Flumes are not to be confused with aqueducts , which are built to transport water; flumes use flowing water to transport materials. Flumes route water from a diversion dam or weir to a desired materiel collection location. Flumes are usually made up of wood , metal or concrete . Many flumes took the form of wooden troughs elevated on trestles , often following

115-779: A combination of the two. Flow measurement flumes typically consist of a converging section, a throat section, and a diverging section. Not all sections, however, need to be present. In the case of the Cutthroat flume , the converging section directly joins the diverging section, resulting in a throat section of no length (hence the term "Cutthroat"). Other flumes omit the diverging section (Montana, USGS Portable Parshall, and HS / H / HL flumes). Flumes offer distinct advantages over sharp-crested weirs: Styles of flow measurement flumes include: Cutthroat , HS / H / HL-type, Khafagi, Montana , RBC, Parshall , Palmer-Bowlus , Trapezoidal, and Venturi Flume . In some nineteenth-century canals,

138-404: A dendritic system, or of cohesive sediments with no bedload transport. Meanders fully develop only when the river banks are sufficiently stabilized to limit lateral flow. An increase in suspended sediment relative to bedload allows the deposition of fine erosion -resistant material on the inside of a curve, which accentuated the curve and in some instances, causes a river to shift from a braided to

161-736: A flood in 1868. It reverted to its old course during Cyclone Gabrielle in February 2023, until the Coronation Park stop bank in Waipawa was repaired on 16 February, returning the Waipawa to its post-1868 course. River quality is sampled at the SH50 bridge. At that site its Macroinvertebrate Community Index is C (of grades A to D) and likely degrading, but it is in the best 25% of rivers for most samples, except clarity. In warm weather cyanobacteria sometimes develop. Other main routes crossing

184-399: A flume is defined as a specially shaped, fixed hydraulic structure that under free-flow conditions forces flow to accelerate in such a manner that the flow rate through the flume can be characterized by a level-to-flow relationship as applied to a single head (level) measurement within the flume. Acceleration is accomplished through a convergence of the sidewalls, a change in floor elevation, or

207-426: A straight channel. Also important to channel development is the proportion of suspended load sediment to bed load . An increase in suspended sediment allowed for the deposition of fine erosion -resistant material on the inside of a curve, which accentuated the curve and in some instances, caused a river to shift from a braided to a meandering profile. These experimental results were expressed in formulas relating

230-402: A variation in sediment load, provided the amount of water carried by the river is unchanged. A threshold slope was experimentally determined to be 0.016 (ft/ft) for a 0.15 cu ft/s (0.0042 m /s) stream with poorly sorted coarse sand. Any slope over this threshold created a braided stream, while any slope under the threshold created a meandering stream or – for very low slopes –

253-403: Is wide agreement that a river becomes braided when it carries an abundant supply of sediments. Experiments with flumes suggest that a river becomes braided when a threshold level of sediment load or slope is reached. On timescales long enough for the river to evolve, a sustained increase in sediment load will increase the bed slope of the river, so that a variation of slope is equivalent to

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276-583: The Rakaia and Waitaki Rivers of New Zealand are not aggrading, due to retreating shorelines, but are nonetheless braided rivers. Variable discharge has also been identified as important in braided rivers, but this may be primarily due to the tendency for frequent floods to reduce bank vegetation and destabilize the banks, rather than because variable discharge is an essential part of braided river formation. Numerical models suggest that bedload transport (movement of sediment particles by rolling or bouncing along

299-676: The Waikamaka River . The Mangaonuku Stream is a tributary on the northern bank, west of Waipawa, near Ruataniwha. The Waipawa's flow is generally greater than that of the Tukituki River, into which it flows. The Old Bed of Waipawa River flows roughly parallel with and north of the present Waipawa River to join the Tukituki through the Papanui Stream, south west of Lake Poukawa . The Waipawa changed its course during

322-461: The Saddle. 39°58′S 176°38′E  /  39.967°S 176.633°E  / -39.967; 176.633 Braided river Braided streams tend to occur in rivers with high sediment loads or coarse grain sizes, and in rivers with steeper slopes than typical rivers with straight or meandering channel patterns. They are also associated with rivers with rapid and frequent variation in

345-437: The amount of water they carry, i.e., with " flashy " rivers, and with rivers with weak banks . Braided channels are found in a variety of environments all over the world, including gravelly mountain streams, sand bed rivers, on alluvial fans , on river deltas , and across depositional plains. A braided river consists of a network of multiple shallow channels that diverge and rejoin around ephemeral braid bars . This gives

368-426: The critical slope for braiding to the discharge and grain size. The higher the discharge, the lower the critical slope, while larger grain size yields a higher critical slope. However, these give only an incomplete picture, and numerical simulations have become increasingly important for understanding braided rivers. Aggradation (net deposition of sediments) favors braided rivers, but is not essential. For example,

391-433: The hydraulic method of gold-mining. A diversionary flume is used to transfer water from one body to another, such as between two reservoirs. Log flumes use the flow of water to carry cut logs and timber downhill, sometimes many miles, to either a sawmill or location for further transport. Some varieties of flumes are used in measuring water flow of a larger channel. When used to measure the flow of water in open channels,

414-517: The natural contours of the land. Originating as a part of a mill race , they were later used in the transportation of logs in the logging industry, known as a log flume . They were also extensively used in hydraulic mining and working placer deposits for gold , tin and other heavy minerals. The term flume comes from the Old French word flum , from the Latin flumen , meaning a river. It

437-546: The river a fancied resemblance to the interwoven strands of a braid . The braid bars, also known as channel bars, branch islands, or accreting islands, are usually unstable and may be completely covered at times of high water. The channels and braid bars are usually highly mobile, with the river layout often changing significantly during flood events. When the islets separating channels are stabilized by vegetation, so that they are more permanent features, they are sometimes called aits or eyots. A braided river differs from

460-553: The river are SH2 and the Palmerston North–Gisborne railway at Waipawa. There are hundreds of banded dotterel (pohowera) and pied stilt around the river. Waipawa Forks Hut provides accommodation close to the headwaters of the river. On the ridge to the north, above the headwaters, is Sunrise Hut. It is the most popular hut in the Ruahine Park and was renovated in 2020. A day walk is possible, via Sunrise and

483-544: The river banks. They are also found on fluvial (stream-dominated) alluvial fans . Extensive braided river systems are found in Alaska , Canada , New Zealand 's South Island , and the Himalayas , which all contain young, rapidly eroding mountains. Flume A flume is a human-made channel for water , in the form of an open declined gravity chute whose walls are raised above the surrounding terrain, in contrast to

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506-414: The river bottom) is essential to formation of braided rivers, with net erosion of sediments at channel divergences and net deposition at convergences. Braiding is reliably reproduced in simulations whenever there is little lateral constraint on flow and there is significant bedload transport. Braiding is not observed in simulations of the extreme cases of pure scour (no deposition taking place), which produces

529-457: Was formerly used for a stream, and particularly for the tail of a mill race . It is used in America for a very narrow gorge running between precipitous rocks, with a stream at the bottom, but more frequently is applied to an artificial channel of wood or other material for the diversion of a stream of water from a river for purposes of irrigation, for running a sawmill, or for various processes in

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