Basins: land area that contributes water to a river system Divide: separates different drainage basins Ex. Drainage basin of Mississippi River

9: Running Water

Factors that determine velocity: Gradient (slope); channel characteristics Shape, size, roughness Discharge: water vol. in stream [ft3/sec] Profile: cross-sectional view used for study Profile usually a smooth, concave up curve Gradient decreases from head to mouth Factors that increase downstream: Velocity, discharge, channel size Factors that decrease downstream: Gradient, channel roughness

Stream Flow

Load: material transported by a stream Types: dissolved load (in solution), suspended load Bed load: slides or rolls on bottom Load related to stream’s competence and capacity Competence: max particle size transported Capacity: max load stream can carry Capacity is related to discharge Deposition caused by: Decrease in velocity, reducing competence Sediment drops out as water flow slows. Sediments: alluvium, well-sorted deposits Base level: lowest point eroded by stream Sea level: ultimate base level Adjustment in base level due to changing conditions Change causes readjustment of stream Increases deposition and erosion

Erosion

Figure 5.14: Resistant rock layer acts as temporary base level.

Features produced by deposition: Deltas: exist in oceans or lakes Natural levees: form parallel to stream channel Back swamps: area behind a levee Yazoo Tributary: runs parallel to mainstream Yazoo does not directly join main stream

Depositional Features

Meander loop in Colorado River

Figure: Erosion and deposition along a meandering stream

Figure: Continued erosion and deposition widens the valley

Figure: Characteristic meandering on flood plain in wide-stream valley; also cutoffs, oxbow lakes can be included

Stream networks form patterns Types: Dendritic, radial Rectangular, trellis Floods are a common hazard Caused by weather Caused by stream interference Engineering efforts: Artificial levees, flood-control

dams channelization

Drainage Patterns and Floods

Flood Plains, (2:38)