|
In physical geography, a channel is a type of landform consisting of the outline of a path of relatively shallow and narrow body of fluid, most commonly the confine of a river, river delta or strait. The word is cognate to ''canal'', and sometimes shows in this form, e.g. the Hood Canal. Most examples of this are fjords in the Pacific Northwest; a notable exception is the Casiquiare canal. All likely share borrowing from Spanish, Portuguese or French. Channels can be either natural or human-made. A channel is typically outlined in terms of its bed and banks. ==Natural channels== Natural channels are formed by fluvial process and are found across the Earth. These are mostly formed by flowing water from the hydrological cycle, though can also be formed by other fluids such as flowing lava. Channels also describe the deeper course through a reef, sand bar, bay, or any shallow body of water. One example is the Columbia River, a river located in the US states of Washington and Oregon, and which empties into the Pacific Ocean in Astoria, Oregon. 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.). During floods, water flow may exceed the capacity of the channel and flood waters will spill out of the channel and across the valley bottom, floodplain or drainage area. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Channel (geography)」の詳細全文を読む スポンサード リンク
|