Term
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Definition
the study of processes and landforms related to rivers meaning "of, relating to, or inhabiting a river or stream" and "produced by the action of a river or stream"
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Term
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Definition
a feature created by running water with identifiable banks
focus on channels formed by rivers in sediments deposited by the river (alluvial channels) |
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Term
| what are alluvial channels (what is alluvium)? |
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Definition
channels formed by rivers in sediments deposited by the river
alluvium - sediment deposited by flowing streams |
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Term
| what is a bedrock channel? |
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Definition
channels cut into solid rock, rather than loose sediment
where rivers carve into rock, slice mountain ranges etc |
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Term
| what is bankfull discharge? |
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Definition
the discharge that just fills the channel, in which the water is at the level of the adjacent floodplain
considered teh channel-forming discharge
the channel form is a reflection of this levle of flow, not higher floods or lower flows
has a recurrence interval of 1.5 years, a flow level that is reached at least 2 out of 3 years |
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Term
| what shapes do alluvial channels take? |
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Definition
1. meandering: the channel bends this way and that, it is sinuous
2. braided: the channel consists of multiple threads, speparated by many small transitory islands
commonly found in rivers that carry lots of gravel and have large variations in discharge |
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Term
| what is the sinuosity ratio? |
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Definition
the length of a river (down the middle of the channel) divided by the straightline distance commonly thought of as the vally length
Sinuosity = Lriver/Lvalley
the more bends in the channel, the greater the sinuosity; if the channel is straight, the sinuosity ratio is one |
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Term
| what is the sinuosity ratio of meandering rivers? |
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Definition
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Term
| if a channel has a sinuosity ratio between 1 and 1.3 what is it considered? |
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Definition
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Term
| What does Luna Leopold say about the distinctions between river forms? |
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Definition
| [image]there's no real distinction, they're all meandering |
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Term
| why is there such similarity in form of rivers over different scales? |
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Definition
| the length of the meander, L (the straight line distance between a pair of bends (right and left)) is proportional to the width of the channel, w, such that on average L=11w |
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Term
| what is the radius of curvature |
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Definition
a way to measure the tightness of the river bends
r, the radius of a circle that scribes the bend
in general, the meander length L is 4.7 times the radius of curvature, L=4.7r |
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Term
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Definition
a deep spot on a channel bottom, often on the side of the channel, not in the middle
flows tend to be fastest here |
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Term
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Definition
| a shallow steep section on a channel bottom, |
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Definition
| the part of the channel with the fastest flow and carrying the most water |
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Term
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Definition
| bars - deposits built up of coarse sediment on the channel bed |
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Term
| how do pools, riffles, bars, and thalwegs relate to eachother? |
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Definition
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Term
| how does the length of a bar relate to the length of the channel? |
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Definition
| the length of each bar unit (or alternately, pool spacing) is about 3-5 channel widths |
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Term
| what is hydraulic geometry? |
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Definition
the relationships between discharge and widgth, depth, velocity, and slope
relationships are considered separaely for the changes at-a-point (at one cross section of a river) and for changes downstream |
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Term
| describe at-a-point hydraulic geometry relationships |
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Definition
as discharge increases:
*channel widdth increases, but does not change much
*channel depth increases. depth increase is much more significant in accommodating extra flow than width changes
*velocity increases
*channel slope (steepmeness of water surface) does not change much with discharge |
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Term
| describe downstream hydraulic geometry relationships |
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Definition
as discharge increases downstream:
*width incrases significantly downstream, increasing proportionally to the square root of discharge
*depth increases significantly downstream, just as depth changes with discharge at a point
*velocity is nearly constant, or only slightly increasing, along the length of a river
*channel slope declines over the length of a river |
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Term
| what have we seen in the hydraulic geometry relationships found in many rivers by Leopold and Maddock? |
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Definition
at a particular point in a river, higher discharge is accomodated mostly by the flow gettting deeper and faster, with relatively little adjustment in width or slope
increasing width and depth accomodates the increase in discharge downstream through a river
velocity does not change much downstream, mostly due to the declining slope |
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