Hydraulic action, Abrasion, Attrition and Solution.
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Hydraulic action is?
the sheer force/power of water
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Abrasion is?
when rocks crash into the river banks
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Attrition is?
rocks colliding and reducing in size
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Solution is?
rocks dissolving
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What changes occur from the source to mouth?
Lots of vertical erosion at the shallow, narrow mouth. Lots of hydraulic action, attrition and abrasion (vertical erosion) at the start. The source is wider and deeper. Lateral erosion and deposition at the source.
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How do waterfalls create gauges?
hard rock on top of soft rock. Overhang created bcos SR is eroded by hydraulic action/abrasion. Overhang collapses. Further erosion creates a plunge pool. The waterfall retreats upstream and a gauge is formed
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How do meanders create oxbow lakes?
Erosion on outside bend. River cliff. On the other side shingle is deposited. Slip off slope. Neck grows narrower due to deposition and erosion. After heavy rain the banks can burst. Path of least recisitance. Cut loop off and oxbow lake forms.
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What are levees?
Raised embankments that flow either side of a river in its lower course
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How are levees formed?
When a river is laden with sediment. The river bursts banks. The velocity of the river cant carry the large load so the load is depositied and builds levees.
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What things effect a river discharge?
Permeable rock allows water through which slows down a river discharge. impermeable rock doesnt allow water through- speeds up. steep sided valleys- faster surface runoff. Heavy urbanisation prevents infiltration into soil so dischrage increases
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Causes of flooding in Bangladesh?
In South Asia, Bay of Bengal. Onshore winds, flat land, monsoon, hurricanes, glaciers melting, sea levels rise, population increase, deforestation, urbanisation, no sewers, lack of recourses
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