Presentation on theme: "9: Running Water Basins: land area that contributes water to a river system Divide: separates different drainage basins Ex. Drainage basin of Mississippi."— Presentation transcript:
1 9: Running WaterBasins: land area that contributes water to a river systemDivide: separates different drainage basinsEx. Drainage basin of Mississippi River
2 Stream Flow Factors that determine velocity: Gradient (slope); channel characteristicsShape, size, roughnessDischarge: water vol. in stream [ft3/sec]Profile: cross-sectional view used for studyProfile usually a smooth, concave up curveGradient decreases from head to mouthFactors that increase downstream:Velocity, discharge, channel sizeFactors that decrease downstream:Gradient, channel roughness
3 Erosion Load: material transported by a stream Types: dissolved load (in solution), suspended loadBed load: slides or rolls on bottomLoad related to stream’s competence and capacityCompetence: max particle size transportedCapacity: max load stream can carryCapacity is related to dischargeDeposition caused by:Decrease in velocity, reducing competenceSediment drops out as water flow slows.Sediments: alluvium, well-sorted depositsBase level: lowest point eroded by streamSea level: ultimate base levelAdjustment in base level due to changing conditionsChange causes readjustment of streamIncreases deposition and erosionFigure 5.14: Resistant rock layer acts astemporary base level.
4 Depositional Features Features produced by deposition:Deltas: exist in oceans or lakesNatural levees: form parallel to stream channelBack swamps: area behind a leveeYazoo Tributary: runs parallel to mainstreamYazoo does not directly join main streamFigure: Erosion and deposition along a meandering streamFigure: Characteristic meandering on flood plain in wide-stream valley; also cutoffs, oxbow lakes can be includedFigure: Continued erosion and deposition widens the valleyMeander loop in Colorado River
5 Drainage Patterns and Floods Stream networks form patternsTypes: Dendritic, radialRectangular, trellisFloods are a common hazardCaused by weatherCaused by stream interferenceEngineering efforts:Artificial levees, flood-control damschannelizationFlood Plains, (2:38)