Physical Definitions

Question 0

Water balance

Answer 0

The balance between inputs and outputs of water in a drainage basin: precipitation = evaporation + transpiration + river flow +/- storage

Question 1

Drainage basin

Answer 1

The area drained by a river and it’s tributaries

Question 2

Attrition

Answer 2

Fragments strike one another, the bed and the banks, reducing their size

Question 3

Abrasion

Corrasion

Answer 3

Scraping of load on bed and banks

Question 4

Corrosion

Answer 4

Minerals in rocks dissolved by weak acids in river water

Question 5

Hydraulic action

Answer 5

Movement of loose material due to frictional drag or moving water on sediment in the bed

Question 6

Erosion

Answer 6

The break up of rocks by the action of rock particles beings moved over the earths surface by water wind and ice

Question 7

Transportation

Answer 7

The movement of particles from the place where they were eroded to the place where they were deposited

Question 8

Traction

Answer 8

Large stones or boulders rolled along the bed by water moving downstream

Question 9

Saltation

Answer 9

Small stones bounce along the channel bed

Question 10

Suspension

Answer 10

Very small particles carried along by river flow

Question 11

Solution

Answer 11

Dissolved minerals are transported within the water

Question 12

Deposition

Answer 12

The laying down of solid material in the form of sediment. Occurs due to a decrease in energy/velocity

Question 13

Competence

Answer 13

A rivers ability to erode and transport particles of a given size

Question 14

V shaped valley causes

Answer 14

Vertical erosion
Large sediment
Heavy rain/snow melt
Depends on climate geology and vegetation

Question 15

Interlocking spurs causes

Answer 15

River winds around spurs or protrusions that appear to interlock

Question 16

Rapids causes

Answer 16

Sudden increase in gradient
Harder bands of rock
More turbulent = more erosive

Question 17

Waterfalls causes

Answer 17

Rapid change in gradient
Resistant rocks underlaid by less resistant beds
Plunge pool = swirling = rapid erosion
Undercuts the bed above - prone to collapse
Waterfall retreats = gorge

Question 18

Potholes causes

Answer 18

Uneven bed causes an “eddy”
Pebbles trapped inside from circular pot holes in the bed
Overtime they merge, lowering the bed

Question 19

Meanders

Answer 19

Alternating pools (deep) and riffles (shallow)
In a pool, channel is more efficient so flow is irregular and max flow or thalweg on one side. 
Increases erosion on one side and deposition on the other - bend
Also causes heliocidal flow - corkscrew - erodes along channel, increases deposition on next inside bend after pool.

Question 20

Oxbow lakes causes

Answer 20

As a result of meanders, during high discharge, it’s more efficient for a river to flow across the neck rather than around it.
When it returns to normal, river follows new course so new oxbow lake is cut off.
(Swans neck meander)

Question 21

Braiding (multiple thread channels) causes

Answer 21

Channel division caused by deposition of sediment
Excessive bed load - poor vegetation
Easily eroded banks ie of gravel and sand
High variable discharge/steel channel gradients

Question 22

Floodplain causes

Answer 22

Meander migration flattens land
Deposition occurs on flat land
Fluvial deposits (alluvium) in times of flood fertilises the land. Friction as deposited.

Question 23

Levees causes

Answer 23

Low ridges of alluvium
Heavier load deposited first - due to friction it is dropped
Builds up to form levees

Question 24

Deltas causes

Answer 24

Occur where fresh water meets salt water Deposition due to deceleration as tides meet river (shallower = friction) Flocculation - charged load sticks together so smaller load deposited -arcuate -cuspate -birds foot -estuarine