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Runoff and Rivers. How Rivers Shape Our Landscape. How do rivers form?. River: A large natural stream that empties into a large body of water such as a lake or ocean. Runoff: precipitation that returns to the sea erodes stream/valley transports sediments (erosion!!!!!) deposits sediments. - PowerPoint PPT Presentation
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How do rivers form?
• River: A large natural stream that empties into a large body of water such as a lake or ocean.
• Runoff: precipitation that returns to the sea– erodes stream/valley– transports sediments (erosion!!!!!)– deposits sediments
River Vocabulary• Capacity: the maximum amount of sediments that a
stream can move (transport)• Stream Load: amount of material a stream can
move (transport). Depends on capacity and type of land.
• Suspended Load: Sediments such as clay that are suspended (floating) in the water.
• Deposition: laying down of sediments• Sorting: deposition by size and density
• the biggest and heaviest (rocks) are always deposited first• silt and clay (very small) settles last
Load: How do rivers transport sediments?
• Three ways a river can carry its load:– Solution: stuff dissolved in the water– Suspension: particle of silt/clay/mud “floating” in
the water– Bed load: heavy stuff (rocks) that roll, bounce or
slide along the bottom
River Calculations
• Gradient-the slope of a river expressed in feet/mile• Velocity-speed expressed feet/second. This can be
calculated by timing a piece of wood floating over a certain distance and then dividing the distance by the time
• CSA (Cross Sectional Area): width x avg. depth• Discharge: velocity x CSA
• Dsi
River Features• Deltas: Fan-shaped area of
deposition at the mouth of a river• Levee-Man made or natural wall
along a river bank that controls flooding
• Tributary-A large stream or small river that flows into an area’s main river.
• Divide-High area that separates drainage basins (ex. Continental Divide)
River Drainage Patterns
• Dendritic: Like tree branches. In areas with some hills.
• Radial: In a circle. Mostly from flowing off a mountain.
• Rectangular: Flat areas.
River Features
• Alluvial Fan: Fan shaped deposits of river transported material called Alluvium.
• Normally found at the base of a mountain. Gold can be found here!
River Features
• Flood Plain: A flat area on either side of a stream, enclosed by a river valley, that floods during periods of excessive rainfall.
Rivers can erode and deposit• A meandering river moves
faster on the outside curve than the inside curve.
• Meander: A loop-like bend in a stream’s path.
• Erosion occurs on the outside curve called the Cut Bank.
• Deposition occurs on the inside curve called the Point Bar.
Oxbow Lake• Oxbow Lake: A lake that forms
when a meander is cut-off from the main stream. Is in a curve shape.
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