River processes

 Topic 6: River processes

Section of the river

Key concepts:

Drainage basin: the area the river system flows through

• Watershed: high – lying area separating drainage basin

• The river system: A river and all its tributaries

• Tributaries: smaller River that flows into a larger river.

• Long profile of a stream: the fall of the river over its length or the height of the river over its

length.

• Catchment area: it’s a high lying area that catches precipitation and drains it into the river.

• Distributaries: When a river breaks up into smaller streams at the mouth of the river.

• River load: materials or debris carried/disturbed by the river e.g. stones, rocks…

• Wetted perimeter: part of the river channel that is in contact with water e.g. banks and river bed.

• Discharge: amount of water that moves past a particular point in a river. Measured in cubic metre per second (cumecs)

Processes taking place in a river

1. Erosion of materials

2. Transportation of materials

3. Deposition of Materials

Describe the processes by which a river erode its channel

a) Hydraulic action: water pushed into cracks/crevices(narrow cracks) of the bank. Air and water compressed, breaks the rock

b) Corrasion/abrasion: Stones and gravel scours/rub the banks and bed of the river

c) Attrition: materials carried grinds(bumping) down other materials carried – reduce in size

d) Solution or corrosion: Acids in the water dissolve certain types of rock (limestone)

Factors affecting erosion

• Load: heavier and sharper load means more erosion

• Velocity: greater velocity means greater speed and greater erosion

• Geology: softer rocks erode fast

• PH: acidic water erodes limestone

• Human impact: deforestation increases run-off

Activity

Explain erosional process of the river processes, clearly state how it takes place.