Rivers (Erosion and Deposition)

   Rivers

Fluvial Erosion and Deposition

Erosion

Processes of Erosion:

Abrasion: When the load of the river collides with the bed and bank causing them to break upAttrition: When the load of the river collides with itself and breaks itself upHydraulic Action: The sheer force or weight of the water collides with the bed and banks causing them to break upSolution: The river water dissolves minerals in the bed, banks and load of the river, causing them to break up

Directions of Erosion:

Vertical: The river cuts down into the landLateral: The river cuts sideways across the landHeadwards:  The river cuts back up its channel

Features of Erosion             Upper Course

V-Shaped valley with interlocking spurs:  eg Devil's Glen near Ashford, Co. WicklowPotholes: eg. The River LiffeyWaterfalls with plunge pools: eg Glencar Waterall, Co. Sligo

Middle Course

Gorge eg The Grand CanyonMeanders (Feature of both fluvial erosion and deposition) eg The River Shannon at ClonmacnoiseOx-Bow Lake (Feauture of both fluvial erosion and deposition) eg The River Shannon at Roosky, Co. Leitrim

Transportation            Processes of Transportation:

Traction: The largest boulders are pushed along the river bed by the river currentSaltation: Slightly smaller bounders are lifted off the river bed when it hasplenty of energy and are carried in the water, when the river's energy decreasesthe boulders are droppedSuspension: Smaller rocks are carried along in the river waterSolution: Dissolved particles are carried along within the water, they are invisible

Deposition           Why deposition occurs

A river's rate of deposition depends on 2 factors:           >A change in velocity           >A change in volume

Features of deposition

Lower Course

Meanders (Both a feature of erosion and deposition) eg Clonmacnoise, Co. OffalyOx-Bow Lakes: (Both a feature of erosion and deposition) eg Roosky, Co LeitrimLevée w/Floodplain eg The Mississippi River near Illinois & River Barrow, north of Newross, Co. WicklowDeltas (Lacustrine (of lakes) and Marine) There are 4 types of river delta                                                         >Marine                                                         >Arcuate  (in a curved shape) eg The Nile                                                         >Esturine eg The River Shannon                                                         > Bird's Foot eg The Mississippi

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