(,rivers, brooks, creeks, etc.)
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Transcript of (,rivers, brooks, creeks, etc.)
Streams
(,rivers, brooks, creeks, etc.)
Processes
• Erosion • Deposition
Loads
• Bed load– gravel– rounder with greater working
• Suspended load– silt
• Dissolved load– salt, lime
Load Carrying Capacity
• Higher velocity flow allow stream to carry:– larger particles– more total load per volume
What Happens When
• Deposition when flow slows• New erosion when flow speeds up
Sorting
• Velocity changes gradually• Slowing: deposit heaviest load• Speeding: remove lightest substrate• Result: particles of same size found
together (sorted)
Common Profile
• Steep and fast in headwaters• Slower near base• Cannot excavate below base level
Drainage Patterns
Determined by substrate characteristics
Dendritic Trellis Radial
Stream Features
Headlands
• V-shaped valleys• Erosion dominates• Alluvial fan at foot of mountain
Bottomlands
• Flat valleys• Deposition dominates• BUT—flow is variable
Bottomland Features
• Floodplains• Meanders• Oxbows• Levees• Yazoo streams
Meanders
• Erosion on outside• cut bank
• Deposition on inside• point bar
• cutoffs• Oxbows
Meandering River
Meander Evolution
Meander Evolution
Meander Evolution
Meander Evolution
Meander Evolution
Meander Evolution
Meander Evolution
Meander cutoff
Oxbow lake
Floods
• Normal• Bank-full discharge ~ 2 years• Deposit on levees, flood plains
Meandering river flooding
Base Level
• Delta: deposits• choke with sediment• many distributary channels• lobes shift• old sediments subside