Geography

1.valleys are influenced by water through the transportation and deposition of sediment (沉积物)   2.areas above valleys are less affected by river, but land there will be changed    3.runnning water smooth irregularities, wear down the topography by erosion and transportation of debris, and fill up the valley by deposition        4.The Green river helped carve Whirlpool Canyon through erosion and by transporting away the rock deposited into the valley bottom         5.streamflow(河流流量): any channeled(有沟的)of water / overland flow(坡面漫流): the unchanneled downslope movement of surface water/     streamflow: the channeled movement of water along a valley bottom         6.a valley is that portion of the terrain in which a drainage(排水) system is established (汇聚的) / a interfluve is the higher land above the valley walls that seperates adjacent(邻近的) valleys        7.swamps and marshes are found in sections of valleys where there isn’t  clearly established drainage system, but may also found on interfluve.       8.the drainage basin consists of a steam’s valley bottom, valley sides, and those portions of the surrounding interfluves that drain toward valley      9.the drainage basin terminates at a drainage divide, which is the line of separation between runoff that descends in the direction of the one drainage basin and runoff that goes toward an adjacent basin.          0.many sub-basins are found within the overall Mississippi River drainage basin.

1. the concept of stream order has been devised to describe the arrangement           2.on sloping ground most particles move downhill by the splash erosion—raindrops erosion (by overland flow)         3.once surface flow is channeled, its ability to erode and transport material is greatly enhanced by the increased volume and velocity of water.  erosion is accomplished in part by the direct hydraulic power of the moving water, which can excavate and transport material from bottom and sides   of channel(by stream water)       4.stream load contains three fractions: dissolved(溶解) load, suspended(缓期的) load, bedload(水流带来的碎石,泥沙             dissolved load: some minerals, mostly salts, are dissolved in the water and carried in solution.

   suspended load: very fine particles of clay and silt are carried in suspension, moving along with the water without ever touching the steambed

   bedload: sand, gravel, and larger rock fragments constitute the bedload

5.stream competence is a measure of the particle size a stream can transport, expressed by the diameter of the largest particles that can be moved

   stream capacity is a measure of the amount of solid material a stream has the potential to transport, normally expressed as the volume of material  passing a given point in the stream channel during a given time interval

6.alluvium(淤积层) is the general term for stream-deposited sediments, it may include all sizes of rock debris, but smaller paritcles constitute by far the bulk of the total. This deposition often exhibit one or more characteristics, such as: alluvial material is smooth and round due to the battering the rock receive from each other as they flow downstream. Alluvial deposits often display distinct strata or layers, due to episodes of deposition following periodic floods. Alluvium is often ‘sorted’, that is often comprised of rocks of just about the same size.

7.in humid regions, the large rivers and most tributaries are perennial streams, that is, permanent.

8.in more arid parts of the world, the impermanent flows are called intermittent streams or seasonal streams if they flow for only part of the year and ephemeral streams if they can carry water only during and immediately after a rain

9.stream channel patterns are generally grouped into four categories-straight, sinuous, meandering, and braided.

0.straight channels are short and uncommon, and usually indicative of strong control by the underlying geologic structure. A line running in the direction of the water and indicating the deepest parts of the channel, called the thalweg, rarely follows a straight path midway between stream banks

1. sinuous channels are much more common than straight. They are winding(绕) channels and are found in almost every type of topographic setting

2.meandering channels exhibit an extraordinarily intricate pattern of smooth curves in which the stream follows serpentine course, twisting and contorting and turning back on itself, forming tightly curved loops(回路; 圈) and then abandoning them, cutting a new and equally twisting course.

3.braided(编织) channels consist of a multiplicity of interwoven(使交织) and interconnected channels separated by low bars or islands of sand, loose debris