An extent of land where water from melting snow and ice and rain drains downhill into a body of water.
100
Which five factors produce fluvial erosion?
Climate!
Vegetation
Land management
Topography
Soil/Rock/Saprolite properties
100
Facts about braided channels? (4)
-Single channel
-Occur where flow divides into a series of braids separated by bars of accumulated sediment
-The bars are covered by water at bankfull stage (so just 1 channel)
-occur in noncohesive sediment with limited vegetation, in bedload dominated channels
100
Facts about islands?
-bars that become vegetated/stabilized
-can persist for a few or thousands of years in the channel
-can also be formed as a combination of factors like: amalgamating previous islands/bars, combination of erosion and accretion, characteristic of anabranching patterns
100
Calculate!
What is the width of Sandy River at
A=450 m^2
D=25 m
18 m
200
What is a dendritic drainage pattern?
This kind of stream occurs in an area with adequate rainfall and no unusual geologic features.
200
What is sheetwash/sheet erosion?
-splashed soil is removed uniformly (no channels)
*demoiselle
200
Facts about meandering rivers? (3)
-Have higher sinuosity (over 1.3)
-Single channel
-Characteristic flow pattern encourages erosion and undercutting of banks on the outside of bends, and deposition (formation of point bars) on the inside of bends.
200
Vertical accretion- formation of a natural levee?
1. Levees build up after many floods
2. Thick and coarse sediments deposited at channel edges
3. Thin and fine sediments deposited over parts of the floodplain
200
Calculate!
What is the average velocity of the Amazon River at-
R=1.9 m
slope=.08
n=.7
5.427 m/s
300
What is a centripetal drainage pattern?
A circular arrangement of streams where water flows inward from all directions towards the center of an area.
More likely in areas with karst topography, in deserts with intermittent stream flow towards a temporary salt lake or basin.
300
Facts on wash load? (2)
-moves at the velocity of water flow
-it is possible to measure the total sediment transport relating sediment concentration per unit of volume and discharge
300
Facts about anabranching rivers? (3)
-Multiple channels separated by vegetated semi-permanent alluvial islands
-Can be low or high energy
-Advantage of an anabranching river is it can concentrate stream flow using its multiple channels, and maximize bed-sediment transport under conditions where there is little opportunity to increase gradient.
300
What is a crevasse splay? (3)
-provides the top of the floodplain with coarser sediment moving in suspension
-proximal landform to a river bank
-produced when natural levees fail (*through erosion and bank seepage during floods)
300
Calculate!
What is the stream power of Paleo River at
Y=(1000 kg/m^3)(9.8 m/s)
Q=500 m^3/s
S=.005
Bonus! What is the specific stream power when w=200 m?
24,500 W/m
122.5W/m^2
400
The four parameters of drainage basin morphometry?
stream order, relief index, circularity index and form factor, drainage density
400
Facts on bed load? (3)
-Bed load moves more slowly than water flow
-Bedforms such as dunes move downstream a few meters a day
-Bed load does not move randomly, but follow a geometric arrangement with bed load waves, dunes, etc.
400
What kind of sediment load does a braided channel carry, and what is the general slope?
Bed load (at over 11% of total), fairly steep gradient
400
What is a river terrace?
-A roughly flat area limited by sloping surfaces on the upslope and downslope sides. They are the remains of old valley floors left sitting on valley sides after river downcutting.
400
Calculate!
What is the Froude number of Big Stream at-
u=7.2 m/s
R=1.5
Bonus! What does the number indicate?
1.87
Supercritical flow
500
What do the variables stand for-
Dd= total L/Da
Bonus!
What does a higher Dd mean?
Dd- Drainage density
Total L- total length of all streams in a basin
Da- Drainage area
High drainage density means that water will drain more quickly into a river and a larger area will be affected by erosion.
500
Reynolds Number Equation, meanings of variables, and what the number determines?
Re=uR/v
Re:Reynolds number
u:velocity
R:hydraulic radius (*also A/P)
v:kinematic viscosity
Determines if flow is laminar, transitional (rare) or turbulent
500
What are the mechanisms for braiding and bar formation? (4)
central bar deposition, transverse bar conversion, chute cutoff, multiple bar dissection
500
What is a bedrock terrace?
-start in valleys where a river cuts down into bedrock to produce a V shaped valley, the floor of which then widens with lateral erosion. This process is then repeated.
500
Calculate!
What is the depth of Long Stream at
v=1.2 m/s
s= .09
n=.004