Exam Questions
Examine the diagrams A, B and C below
Name each of the three river drainage patterns
Explain the formation of any two Irish landforms
caused by surface processes with the aid of
diagrams
Keywords – Introduction to Rivers
Hydrological Cycle
Basin
Watershed
Source
Tributaries
Confluence
Mouth
Discharge
Long Profile
Base Level
Dendritic Drainage
• One major river with several small tributaries; the network of streams resembles the branches of a tree converging upon the trunk.
• This pattern will occur on any rock type.
• Rivers Shannon and Boyne are examples of this pattern
Trellis Pattern
• Tributaries flow at right
angles into a main river.
This is because the
surface consists of
alternating hard and soft
rock; the streams erode
the softer rock but find it
difficult to break through
the hard rock
• E.g. the Blackwater River
Radial Pattern
• This pattern will develop
in upland areas where
several streams will flow
outwards and
downwards from a
central point. The various
streams will flow in
different directions
• E.g. Slieve Beagh Co.
Monahan
River Erosion
Keywords
Erosion
Lateral
Vertical
Hydraulic Action
Cavitation
Abrasion
Corrasion
Solution
Attrition
Erosion
• When the river channel is widened it is called
lateral erosion
• Vertical Erosion is the deepening of the river
bed
Name: MeanderExample
River Boyne in Co. Meath
Description
S shaped bends in a river
Formation
Main processes:
• Lateral erosion
• Hydraulic Action
• Abrasion
• Deposition
Meander
• A meander is a curve in the river. It happens when the river meets a bend.
• As the river flows around it erodes the outside of the bend as the strongest flow is here. This causes a river cliff
• Slacker or shallower water flows on the inside of the bend and have less power deposition happens. This area of deposition is called a point bar
Name Ox Bow Lakes
Example
River Moy Co. Mayo
Description
Oxbow lakes are the remains of meanders that have been cut off from the rivers course.
Formation
Main Processes
Erosion and Deposition
Ox Bow Lakes
• Ox bow lakes forms when a meander becomes very pronounced.
• A narrow neck develops and in times of flood the main flow cuts across the neck to flow straight.
• It cuts off the loop of the meander and becomes an ox bow lake.
Name Flood Plain
Example
River Suir Co. Waterford
Description
A flat area of land either side of a river
Formation
Main Processes Flooding Deposition
Flood Plain
• As a river meanders the land on either side is
gradually worn back into bluffs of higher land.
• It is the flat land in the centre of a valley
Deposition
A river deposits material due to a reduction in
energy. This generally occurs because of
1. Decreasing Velocity
2. Increase in Volume
3. Increase in the size of its load due to
• A fast flowing tributary adding extra material
• Heavy rainfall
Name Levee
Example
River Moy Co. Mayo
Description
A ridge of sediment deposited on river banks
Formation
Deposition
Name Delta
Example Shannon Estuary
Description
Areas of land at the mouth of a river made form deposits of sand and gravel.
Formation
Deposition
A delta forms where a river reaches a sea or lake. It slows down, loses power and deposits the material it has been carrying.
If the sea is sheltered and there is not much wave action this material will build up into a delta.
As it is deposited it falls into different layers
It blocks up the river channel forcing it to break up into smaller river channels called distributaries.