Rivers (Erosion and Deposition)

Página 1

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 up

Attrition: When the load of the river collides with itself and breaks itself up

Hydraulic Action: The sheer force or weight of the water collides with the bed and banks causing them to break up

Solution: 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 land

Lateral: The river cuts sideways across the land

Headwards: 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. Wicklow

Potholes: eg. The River Liffey

Waterfalls with plunge pools: eg Glencar Waterall, Co. Sligo

Middle Course

Gorge eg The Grand Canyon

Meanders (Feature of both fluvial erosion and deposition) eg The River Shannon at Clonmacnoise

Ox-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 current

Saltation: Slightly smaller bounders are lifted off the river bed when it has

plenty of energy and are carried in the water, when the river's energy decreases

the boulders are dropped

Suspension: Smaller rocks are carried along in the river water

Solution: 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. Offaly

Ox-Bow Lakes: (Both a feature of erosion and deposition) eg Roosky, Co Leitrim

Levée w/Floodplain eg The Mississippi River near Illinois & River Barrow, north of Newross, Co. Wicklow

Deltas (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

New Page