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The water in this stream forms varying currents as it makes its way downhill. In hydrology, a current in a water body is the flow of water in any one particular direction. The current varies spatially as well as temporally, dependent upon the flow volume of water, stream gradient, and channel geometry.
The boat is pulling itself upstream on a cable laid along the river. The rope is wrapped around a central shaft driven by two, side-mounted water wheels (see upper diagram). Behind the river craft is a small boat-like object being pulled by the current, that is holding the cable taut and thus ensuring the necessary friction on the shaft. [4] [5]
A bore in Morecambe Bay, in the United Kingdom Video of the Arnside Bore, in the United Kingdom The tidal bore in Upper Cook Inlet, in Alaska. A tidal bore, [1] often simply given as bore in context, is a tidal phenomenon in which the leading edge of the incoming tide forms a wave (or waves) of water that travels up a river or narrow bay, reversing the direction of the river or bay's current.
The wave travels upstream against the river current at a speed of 13 to 21 km/h (8 to 13 mph). [5] In the lower, broader part of the estuary near Avonmouth, the tidal surge advances as a slight roll in the deepwater channels and the water rapidly spreads across the sands and mudbanks. Often, the Severn Bore floods the lower village of Pill if ...
As a result, antidunes migrate in an upstream direction, counter to the current flow. Antidunes are called in-phase bedforms, meaning that the water surface elevation mimics the bed elevation; this is due to the supercritical flow regime. Antidune bedforms evolve rapidly, growing in amplitude as they migrate upstream.
A tidal bore is a hydraulic jump which occurs when the incoming tide forms a wave (or waves) of water that travel up a river or narrow bay against the direction of the current. [16] As is true for hydraulic jumps in general, bores take on various forms depending upon the difference in the waterlevel upstream and down, ranging from an undular ...
During the highest tides, rising water is funnelled up the estuary into the Severn bore, a self-reinforcing solitary wave that travels rapidly upstream against the river current. [10] West of the line between Lavernock Point and Sand Point is the Bristol Channel, which in turn discharges into the Celtic Sea and the wider Atlantic Ocean.
(The most extreme case of tracking was in the Three Gorges in China where all boats had to be pulled upstream against the current of the Yangtze River.) In worse conditions, the 'demi-chargé' technique was used. Half the cargo was unloaded, the canoe forced upstream, unloaded and then returned downstream to pick up the remaining half of the cargo.