GEOL 101 Lecture 27: Geo 101 Lecture 27

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GEOL 101
Paul Giesting

Monday, April 3, 2017 Lecture 27 Rivers - drainage basing- a land area drained by a stream and its tributaries - only .03% of all water on Earth is running water in streams and lakes - Stage • measurement of the height of the water level of a river • not generally the same as depth- different at different points • arbitrary zero is chosen for given point - Discharge • amount of water flowing past a specific place along stream • depends on water velocity and cross sectional size of a stream • water cross section X velocity (cubic meters/sec) - water cross section- width times the depth of the water in a channel - velocity- how fast water is moving - How water flows • streamlines flow parallel without turbulent mixing (laminar flow) • streamlines cross causing turbulent mixing (turbulent flow) - Competence and capacity • competence and capacity- streams ability to carry solid particles • competence- measure of the maximum size particle a stream can transport under a given set of flow conditions - the faster the flow, the greater the competence • capacity- measure of total volume of sediment stream can transport under a given set of flow conditions - the greater amount of flowing water, the larger the capacity 1 Monday, April 3, 2017 - Three types of sediment transport • dissolved load- amount of chemical compounds carried in a solution by the stream - many minerals and organic compounds can be dissolved by water - acid mine runoff can contain dangerous dissolved chemicals • suspended load- in suspension, which means it is sinking slowly enough that the water current can keep it off the stream bottom - mostly fine grained sediment - usually the most visually obvious • bed load- coarser grained sediment transported along the bottom of the stream bed by rolling and sliding - in terms of erosional work, grinding action of bed load is important - particles that make up the bed load move along the bottom by rolling and sliding and saltation • settling velocity- how fast a sediment will fall through still water - type and amount of material carried in suspension depends on water velocity and settling velocity - during floods, the amount of the suspended load carried by the river can significantly increase • saltation- sediment that move by appearing to hop - occurs as particles are propelled upward by collisions or lifted by the current and briefly carried downstream - heavy par
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