Explain the geographic characteristics of river channel through various sections of its run and their significance in recreational planning
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Answer:
Channel initiation refers to the site on a mountain slope where water begins to flow between identifiable banks. The channel head is the most up-slope part of a channel network and is defined by flowing water between defined identifiable banks.
Overland flow is a primary factor in channel initiation where saturation overland flow deepens to increase shear stress and begin channel incision.Overland flows converge in topographical depressions where channel initiation begins. Soil composition, vegetation, precipitation, and topography dictate the amount and rate of overland flow. The composition of a soil determines how quickly saturation occurs and cohesive strength retards the entering of material from overland flows. Vegetation slows infiltration rates during precipitation events and plant roots anchor soil on hill-slopes.
Natural channels
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Natural channels are formed by fluvial process and are found across the Earth. These are mostly formed by flowing water from the hydro-logical cycle, though can also be formed by other fluids such as flowing lava can form lava channels. Channels also describe the deeper course through a reef, sand bar, bay, or any shallow body of water. An example of a river running through a sand bar is the Columbia Bar—the mouth of the Columbia river.
A stream channel is the physical confine of a stream (river) consisting of a bed and stream banks. Stream channels exist in a variety of geometries. Stream channel development is controlled by both water and sediment movement. There is a difference between low gradient streams (less than a couple of percent in gradient or slightly sloped) and high gradient streams (steeply sloped). A wide variety of stream channel types can be distinguished (e.g. braided rivers, wandering rivers, single-thread sinuous rivers etc.).
Examples of rivers that are trapped in their channels: Grand Canyon and Black Canyon.
Water-flow channels
The channel form is described in terms of geometry (plan, cross-sections, profile) enclosed by the materials of its bed and banks. This form is under influence of two major forces: water discharge and sediment supply. For erodible channels the mutual dependence of its parameters may be qualitatively described by the Lane's Principle (also known as the Lane's relationship) the product of the sediment load and bed grain size is proportional to the product of discharge and channel slope.
Nautical channels
Wooden pilings mark the navigable channel for vessels entering Lake George from the St. Johns River in Florida.
It is especially used as a nautical term to mean the dredged and marked lane of safe travel which a cognizant governmental entity guarantees to have a minimum depth across its specified minimum width to all vessels transiting a body of water . The term not only includes the deep-dredged ship-navigable parts of an estuary or river leading to port facilities, but also to lesser channels accessing boat port-facilities such as marinas. When dredged channels traverse bay mud or sandy bottoms, repeated dredging is often necessary because of the unstable subsequent movement of deeper sea soils.
Extraterrestrial channels
Extraterrestrial natural channels are found elsewhere in the Solar System than the Earth and the longest and widest of which are the outflow channels on Mars and the channels of Venus many of which are tens of kilometers wide (the network of channels flowing from Mars for example is 8000 km in length and the Venus is 7000 km compared to the 6,650 km Nile, the largest active channel on Earth). The exact formation of these large ancient channels is unknown although it is theorized that those on Mars may have been formed due to catastrophic flooding and on Venus by lava flow. In planetary science the term "Rile" is sometimes used for similar formations found on The Moon and Mercury that are of inconclusive origin.