Rivers

RIVERS

what is a drainage basin?:
an area if land drained by a river and its tribuataries

source: start of a river

tributary: a small stream that joins a larger river
confluence: the place where a tribuatary joins a larger river

watershed: the edge of a river basin

How does the cross profile change?

V-shaped valley:
Valley: steep-sided, V-shaped
River: narrow, shallow and turblent

Floodplain:
Valley: wider, flat floor
River: wider and deeper

Levees:
Valley: very wide and flat
River: wide, deep, with large sediment load

How does a rivers long profile change?

it varies
e.g a waterfall creates a step in the long profile

EROSION

hydraulic action:
the force of the water hitting the river bed and banks. Most effective when water is moving fast and at high volume

abrasion: the load carried by the river hits the bed or banks, dislodging particles

attrition; stones carried by the river knock against each other becoming smaller, more rounded

solution: alkaline rocks. e.g limestone. are dissolved by slightly acidic river water.

TRANSPORTATION

solution: dissolved load

Suspension: small sediment held in the river

Traction - large particles rolled on the riverbed

Saltation - 'bouncing' of particles too heavy to be suspended

WHEN DOES DEPOSITION HAPPEN

when a river velocity decreases and it no longer has the ebergy to transport its load, it deposits it.

larger rocks are transported mainly by traction are only carried short distances during periods of high flow. THey are deposited in a rivers upper course. 

Smaller sediment is carried further downstream- mostly in suspension. It is deposited on a rivers bed and banks where velocity slows due to friction.

Lots of deposition occurs at a rivers mouth where its velocity reduces because of the gentle gradient and also by interaction with tides.

RIVER ERIOSION LANDFORMS

interlocking spurs:

a mountain stream erodes vertically created a V-shaped valley. it winds around areas of resistant to create…