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The terminologies you need to know
Source - The beginning of a river
Confluence - Where two large rivers meet
Mouth - Where a river flows (ending) into a lake or the sea
Tributary - A small river or stream that flows into a larger river
Distributary -is a stream that branches off and flows away from a main channel. They are common feature of river deltas. The phenomenon is also known as river bifurcation.
Drainage basin- The area drained by a river and its tributaries, bounded by a watershed
Watershed - An area of high land between two separate drainage basins
Estuary- The section of the river near the mouth that experiences tidal currents
The long profile of a river shows how a river changes in height or gradient along its course from source to mouth.
The cross profile of a river shows the changes in shape from one side of the valley to the other.
Evaporation- when water on the surface heats up and become vapour.
Transpiration- is the release of water molecules in the air by vegetation.
Condensation- water vapour in the air cools down and changes back to liquid, forming cloud.
Precipitation- condensed water that falls down to the earth surface as rain, snow, hail etc.
Infiltration- downward movement of water through tiny pores in the soil.
Percolation- infiltration of water into the deeper level recharging groundwater.
Through-flow- horizontal movement of water through the pore spaces.
Overland flow or surface runoff- is the fastest process of water movement over the surface when the ground becomes saturated and can no longer absorb water.
Water table- beginning of saturated zone inside the ground where all the pore spaces are filled with water. The water table can go up and down depending on the amount of rainfall and the amount of water being used.
Drainage basin- it denotes the area drained by a river and its tributaries, surrounded by a watershed.
Components of a drainage basin- main stream, tributaries and distributaries, wetland and estuary (mouth of a river which is tidal), the exit of the basin (where the waters join another water body such as a river, lake, sea, or ocean)
Watershed or water divide- is an imaginary line that separates adjacent drainage basins. It is generally a highlands or ridge or plateau.

Colorado River and Grand Canyon
From source to mouth


Colorado river basin (National Geographic)
River processes


River erosional processes

River erosion is the wearing away of the riverbed and its banks. It also involve the wearing away of rocks and particles being carried by a river.
Hydraulic Action - This is when the sheer force of the river water dislodges particles (involves loosening of unconsolidated rock particles) from the rivers banks and bed. On the other hand, water and air get trapped into the cracks in river’s banks and bed and cause erosion through increased pressure.
Abrasion or Corrasion - This is where rocks and pebbles that are dragged along the riverbed rub and crash against the river banks and bed and wearing it away. It is also known as sandpapering action.
Attrition - The rocks and pebbles that are transported by a river knock together, collide, break up and become smaller, more rounded and smoother further down a river.
Solution or Corrosion - The river water (is slightly acidic) can dissolve rocks by setting up chemical reaction as in limestone and dolomite topography.

River Landforms

Upper courses
Middle courses
Lower courses
Steep gradient- narrow V shaped valley
Potholes
Interlocking spurs and gorges
Waterfall, rapids
Asymmetrical channel
Flood plain
meanders
Wide-broad channel
Ox-bow lakes
Large flood plains
Levees
Braided channel
Deltas

Steep sided gorges and interlocking spurs
Vertical erosion leads to the development of steep sided, narrow V shaped valleys in the upper course of a river by the process of undercutting, known as gorges.
Waterfall retreats to upstream also cause steep sided gorges.
In the upper course, the river itself is forced to adopt a winding course around projected hill-sides as headward erosion may not be sufficient enough to cut though the hard rocks of a mountain wall. This winding course around protruding hillsides is called interlocking spurs. Interlocking spurs restricts the view up or down the valley.

Rapids and Waterfall
Forms when there is a sudden interruption in the course of a river caused by the differential erosion of hard and soft rocks, sea level changes or faulting.
Waterfall and rapid creation depend on the disposition of the geological strata. Waterfall form where a horizontal layer of hard rock lies on the top of a layer of soft rock in a river valley.
Rapids and waterfall are the sudden interruption in the course of a river. A knick point denotes a sharp change in the channel slope. Rapids occur where the layers of hard and soft rocks are very thin and therefore no obvious break of slope develops as in waterfall.
Process
Soft rock underneath is eroded more rapidly causing a drop in river bed, known as Knick point (mark a sharp break in slope). Gradually a plunge pool will be created at the base of a knick point. In time the overlying harder rock will worn away through differential erosion. The unsupported hard rock will collapse into its plunge pool.
As the plunge pool enlarges due to repetition of the same process, the waterfall begins to retreat. Waterfall retreats may create steep sided river valley known as gorge.

Meandering Channel and formation of Ox-bow Lake
Meanders are large bends common in the middle and lower courses of a river, form as result of both erosion and deposition Meanders constantly change their shape and position.

Helical Flow: The water in a river flow naturally in a pattern that transmits energy to the sides. The Fastest current is forced to the outer bend.

Outside bank- of a meander where the full force of a river is felt is steep and marked by undercut. Small river cliff or bluff is formed at the outside bank.

Slip off slope- inner bend of a meander where water flow is slack and deposition is very active. Deposition may form point bar at this side.

Ox-bow Lake forms both as a result of erosion and deposition. Erosion is the dominant process at the outer bend of the meander due to helical flow of the river. It creates large meander loop. Erosion during flood at the river neck joins the meander neck. Deposition seals inner bend of the meander and river start to flows in new channel and the cut off part of the old course form ox-bow lake.

Formation of waterfall
Middle course of River Tees


Meanders and Ox bow lake of River Tees
River Tee's Estuary



Three Gorges Dam