Option A - Drainage basin hydrology and geomorphology

Question 1

Drainage basin

Answer 1

an area within which water supplied by precipitation is transferred to the ocean, a lake or a larger stream. It includes all the area drained by a river and its tributaries

Question 2

Freshwater

Answer 2

includes rivers, lakes, wetlands, groundwater, glaciers and ice caps.

Question 3

Source

Answer 3

the area in which a river begins

Question 4

Mouth

Answer 4

where a river ends its journey, flowing into the sea or a lake

Question 5

Tributary

Answer 5

a smaller river that joins a larger river

Question 6

Confluence

Answer 6

the point at which two rivers join

Question 7

Watershed

Answer 7

the boundary between two drainage basins marked by a ridge of high land

Question 8

Drainage density

Answer 8

the total length of all the streams in the basin divided by the total area of the basin.

Question 9

The hydrological cycle (water cycle)

Answer 9

the continuous exchange of water between land and the atmosphere. Approximately 97% of the Earth’s water is stored in the oceans, and only a fraction of the remaining portion is usable freshwater.

Question 10

River discharge

Answer 10

the volume of water passing a given point over a set time.

Question 11

Bradshaw model

Answer 11

a theoretical model that helps describe the chanegs we would expect as a river travels from its source region in its upper course with increasing distance downstream.

Question 12

Name the changes as the river flows downstream for: velocity, discharge, width and depth, gradient, load, wetted perimeter and channel bed roughness.

Answer 12

velocity generally increases downstream as more water is added to rivers via tributary rivers.

discharge increases downstream as tributaries swell the amount of water and velocity increases as channels become smoother and less rough

width and depth increase downstream as more water is added from tributaries

gradient decreases as rivers flow because the river meanders across the land rather than erode into it and follow a straight path as it does in the source.

load decreases downstream and the stones get rounder and smoother as they are eroded

wetted perimeter increases downstream as water feeds into main streams from tributary rivers

hydraulic action increases as the stream should increase in size and thus power

channel bed - Less rough/turblent downstream due to erosion

Question 13

Erosion

Answer 13

involves the wearing away of rock and soil found along the river and banks. Erosion also involves the breaking down of the rock particles being carried downstream by the river.

Question 14

Four types of erosion

Answer 14

corrasion/abrasion
corrosion
hydraulic action
attrition

Question 15

Corrasion/abrasion

Answer 15

the wearing away of the bed and bank by the load carried by a river.

Question 16

Attrition

Answer 16

the wearing away of the load carried by a river. It creates smaller, rounder particles.

Question 17

Hydraulic action

Answer 17

the force of air and water on the sides of rivers and in cracks.

Question 18

Corrosion/solution

Answer 18

the removal of chemical ions, especially calcium.

Question 19

Factors that affect rates of erosion

Answer 19

load
gradient
pH
geology
velocity
human impact

Question 20

Vertical erosion

Answer 20

when the river cuts down vertically into the ground to create a V-shaped valley

Question 21

Lateral erosion

Answer 21

when a river erodes laterally (sideways) across the valley, creating a flat valley bottom.

Question 22

Methods of transportation in river

Answer 22

traction
saltation
suspension
solution

Question 23

Traction

Answer 23

larger boulders and rocks are rolled along the river bed.

Question 24

Saltation

Answer 24

small pebbles and stones are bounced along the river bed

Question 25

Suspension

Answer 25

fine, light material is carried along by the river

Question 26

Solution

Answer 26

minerals are dissolved in the water. This is a chemical change.

Question 27

Deposition

Answer 27

the geological process in which sediments, soil and rocks are added to a landform or land mass because the water losses energy and is forced to drop them.

Question 28

Waterfall

Answer 28

water dropping from a higher to lower point, sometimes a great height, from a river or stream

Question 29

Formation of waterfall

Answer 29

The soft rock is undercut by hydraulic action (force of air and water on the sides of rivers and oceans)
Abrasion of soft rock occurs
Lack of support by soft rock
Weight of water causes unsupported hard rock to collapse and retreat

Question 30

Flood plains

Answer 30

areas of low relief formed by deposition when a river floods.

Question 31

Meander

Answer 31

a winding curve of bend in a river

Question 32

Oxbow lake

Answer 32

a U-shaped lake that forms when a wide meander from the main river is cut off

Question 33

Formation of meanders and oxbow lakes

Answer 33

Due to banks of sediment at the bottom of the river (deposited at times of low flow), the river weaves around these alternating shallow and deeper sections on what was initially straight channel.
This movement targets one bank of the section leading to erosion (abrasion and hydraulic action) and becomes the outside bend of the meander.
Further erosion narrows the gap between the two arms of river. When it floods, the river breaks through narrow gap.
Eventually the neck of the meander will be breached by the river creating an oxbow lake.

Question 34

Levees

Answer 34

embankments built to prevent the overflow of a river.

Question 35

Formation of levees

Answer 35

During a flood, water overflows the river banks and existing levees until it reaches the end of the floodplain. Rocks, gravel, mud and smaller material is lifted up and transported onto the floodplains.
Deposition occurs - the bigger the material, the closer it is to the river bank, and vice versa with small materials. The material is deposited according to its size. Full deposition occurs when the water retreats - Horizontal Sorting.
After water has retreated, levees are created and the river level increases. It can also take material back to the river source and be deposited there. This is why the river may flow above the level of floodplain.

Question 36

Braided channels

Answer 36

a channel that consists of a network of smaller channels separated by small and temporary islands called ‘eyots’ or ‘braided bars’.

Question 37

Formation of braided channels

Answer 37

There is a build of sediment where water flow is slow - causes changes in the direction of the river and create new channels.
This can occur to form a delta - one type of braided channels.

Question 38

Delta

Answer 38

formed when a stream flows into a standing body of water.

Question 39

Formation of delta

Answer 39

A river needs to carry a large volume of sediment.

Deposition is increased if the water is salty (salt particles group together) and become heavier, so they are deposited.