chapter 4: weathering and erosion topic 6 : river deposits ; flooding
TRANSCRIPT
![Page 1: Chapter 4: Weathering and Erosion TOPIC 6 : River Deposits ; Flooding](https://reader035.vdocuments.mx/reader035/viewer/2022062314/56649f1b5503460f94c30d78/html5/thumbnails/1.jpg)
Chapter 4: Weathering and Erosion
TOPIC 6 : River Deposits ; Flooding
![Page 2: Chapter 4: Weathering and Erosion TOPIC 6 : River Deposits ; Flooding](https://reader035.vdocuments.mx/reader035/viewer/2022062314/56649f1b5503460f94c30d78/html5/thumbnails/2.jpg)
Deposition
• The amount and size of a river’s load depends on discharge, which in turn depends on speed.
• When a river slows down, it loses it’s ability to carry some of it’s load.
• Some of the load gets deposited where the river loses speed. Heaviest load (bedload) is the first to get deposited.
![Page 3: Chapter 4: Weathering and Erosion TOPIC 6 : River Deposits ; Flooding](https://reader035.vdocuments.mx/reader035/viewer/2022062314/56649f1b5503460f94c30d78/html5/thumbnails/3.jpg)
Deposition locations
• The inside bank of meanders (looping bends)– In sharp turns, water on the inside of the turn
slows down while it speeds up on the outside bank. (inside = deposition ; outside = erosion)
• Near and at the mouth of a river– As rivers approach their base level (elevation
of what they are flowing into) they lose most of their gradient and speed.
![Page 4: Chapter 4: Weathering and Erosion TOPIC 6 : River Deposits ; Flooding](https://reader035.vdocuments.mx/reader035/viewer/2022062314/56649f1b5503460f94c30d78/html5/thumbnails/4.jpg)
Depositional Features of Rivers
• POINT BARS and FLOODPLAINS– Form along the inside bank of meanders– Point bars = rocks, gravel, sand– Floodplains = soil (sand, silt, clay)
• Flat areas of fertile soil that form along the banks of a river and are covered by water during flood stage.
• DELTAS and ALLUVIAL FANS– Fan-shaped land formed at the mouth of a
river from deposits of fertile sediment.
![Page 5: Chapter 4: Weathering and Erosion TOPIC 6 : River Deposits ; Flooding](https://reader035.vdocuments.mx/reader035/viewer/2022062314/56649f1b5503460f94c30d78/html5/thumbnails/5.jpg)
CUT BANK
![Page 6: Chapter 4: Weathering and Erosion TOPIC 6 : River Deposits ; Flooding](https://reader035.vdocuments.mx/reader035/viewer/2022062314/56649f1b5503460f94c30d78/html5/thumbnails/6.jpg)
POINT BAR
![Page 7: Chapter 4: Weathering and Erosion TOPIC 6 : River Deposits ; Flooding](https://reader035.vdocuments.mx/reader035/viewer/2022062314/56649f1b5503460f94c30d78/html5/thumbnails/7.jpg)
![Page 8: Chapter 4: Weathering and Erosion TOPIC 6 : River Deposits ; Flooding](https://reader035.vdocuments.mx/reader035/viewer/2022062314/56649f1b5503460f94c30d78/html5/thumbnails/8.jpg)
Cut Bank
CUT BANK
![Page 9: Chapter 4: Weathering and Erosion TOPIC 6 : River Deposits ; Flooding](https://reader035.vdocuments.mx/reader035/viewer/2022062314/56649f1b5503460f94c30d78/html5/thumbnails/9.jpg)
Cut Bank Erosion
![Page 10: Chapter 4: Weathering and Erosion TOPIC 6 : River Deposits ; Flooding](https://reader035.vdocuments.mx/reader035/viewer/2022062314/56649f1b5503460f94c30d78/html5/thumbnails/10.jpg)
meandersfloodplain
![Page 11: Chapter 4: Weathering and Erosion TOPIC 6 : River Deposits ; Flooding](https://reader035.vdocuments.mx/reader035/viewer/2022062314/56649f1b5503460f94c30d78/html5/thumbnails/11.jpg)
![Page 12: Chapter 4: Weathering and Erosion TOPIC 6 : River Deposits ; Flooding](https://reader035.vdocuments.mx/reader035/viewer/2022062314/56649f1b5503460f94c30d78/html5/thumbnails/12.jpg)
Formation of Point Bars and Floodplains
• http://csdms.colorado.edu/wiki/Movie:Floodplain_Evolution
• Stream table meandering
![Page 14: Chapter 4: Weathering and Erosion TOPIC 6 : River Deposits ; Flooding](https://reader035.vdocuments.mx/reader035/viewer/2022062314/56649f1b5503460f94c30d78/html5/thumbnails/14.jpg)
![Page 15: Chapter 4: Weathering and Erosion TOPIC 6 : River Deposits ; Flooding](https://reader035.vdocuments.mx/reader035/viewer/2022062314/56649f1b5503460f94c30d78/html5/thumbnails/15.jpg)
The Nile Delta (Eqypt)
![Page 16: Chapter 4: Weathering and Erosion TOPIC 6 : River Deposits ; Flooding](https://reader035.vdocuments.mx/reader035/viewer/2022062314/56649f1b5503460f94c30d78/html5/thumbnails/16.jpg)
![Page 17: Chapter 4: Weathering and Erosion TOPIC 6 : River Deposits ; Flooding](https://reader035.vdocuments.mx/reader035/viewer/2022062314/56649f1b5503460f94c30d78/html5/thumbnails/17.jpg)
Benefits and dangers of rivers
• In addition to providing fresh water, river deposits produce very fertile farmland.
• Floodplains and deltas are among the most fertile areas for farming.
• Floodplains and deltas are prone to flooding when rivers overflow their banks (known as “flood stage”). Crops and structures built on these may be destroyed during floods.
![Page 18: Chapter 4: Weathering and Erosion TOPIC 6 : River Deposits ; Flooding](https://reader035.vdocuments.mx/reader035/viewer/2022062314/56649f1b5503460f94c30d78/html5/thumbnails/18.jpg)
Controlling the river
• The risk of flooding can be controlled by the construction of:– Dams – a barrier that redirects the flow of
water to another area; controls how much water flows through the channel.
• Dams can also use the energy of a river to produce mechanical or electrical energy.
– Levees – a barrier built along the banks of a river to prevent overflow during flood stage.
![Page 19: Chapter 4: Weathering and Erosion TOPIC 6 : River Deposits ; Flooding](https://reader035.vdocuments.mx/reader035/viewer/2022062314/56649f1b5503460f94c30d78/html5/thumbnails/19.jpg)
Taming the River- Dams
A dam
![Page 20: Chapter 4: Weathering and Erosion TOPIC 6 : River Deposits ; Flooding](https://reader035.vdocuments.mx/reader035/viewer/2022062314/56649f1b5503460f94c30d78/html5/thumbnails/20.jpg)
Levee
![Page 21: Chapter 4: Weathering and Erosion TOPIC 6 : River Deposits ; Flooding](https://reader035.vdocuments.mx/reader035/viewer/2022062314/56649f1b5503460f94c30d78/html5/thumbnails/21.jpg)
This guy really wants to be left alone!