Rivers

1

A waterfall is formed when a river flows on top of a band of hard rock e.g. granite and a band of soft rock e.g. limestone.

2

As the river flows over the bands, processes of hydraulic action and abrasion erode the soft rock. This causes vertical erosion down into the river channel forming a waterfall

3

At the base of the waterfall, a plunge pool is formed. As water is falls into the plunge pool, it splashes against the back wall eroding it even more. This causes undercutting

4

Undercutting erodes the soft rock and leaves an overhang of the hard rock, which collapses

5

This process repeats and the waterfall retreats upstream

Example

Torc Waterfall, Co. Kerry

Source

The beginning of a river

Course

The route a river takes to the sea

Confluence

The point at which two rivers join

Tributary

A small river

Mouth

Where a river ends

Drainage basin

The area of land drained by a river

Watershed

Area of high land that separates two drainage basins

Estuary

The tidal part of a river

Hydraulic Action

The physical force of moving water that breaks down rocks from the riverbed and banks

Abrasion

Small stones carried by the river wear away riverbeds and banks

Attrition

Small stones collide into each other and break into smaller pieces

Solution

Acids in the water dissolve rocks e.g. limestone

Feature of a youthful stage & explain what it is

A waterfall is a vertical drop in the youthful stage

Example of a waterfall

Torc Waterfall, Co Kerry

What is a feature of river deposition?

A levee is a long ridge of alluvium that runs along the edge of a river

Formed in the Old Stage of a river

What is HEP?

-Hydroelectric Power is the creation of electricity by using the force of falling water

Dendritic

Where tributaries combine before joining the main river. 

Trellis

Where tributaries join another tributary or the main river at a 90° angle.

Radial

This is where streams flow down from a central high point. It looks like the spokes on a bicycle wheel.

Deranged

There is no clear pattern.

Why did the River Shannon flood?

Unusually high levels of rainfall, lack of planning and buildings on flood plains

What were the immediate impacts of the flood?

Agricultural land covered in water
Livestock lost
Thousands of homes flooded
Roads/infrastructures damage
Businesses shut during Chrismastime
Water unsafe to drink

What were the government responses to the flood?

Army deployed with sandbags & pumps
Emergency accommodation was set up
Local councils were given €16m
€85m was given to repair roads/infrastructures
It cost €106m overall

What were the long term solutions?

Flood defenses were put to prevent future floods
The river was dredged to deepen the river channel
A national flooding forecast was set up with a waring service
Shannon Flood Risk Group created to control floods for the Shannon

Advantages of HEP

Provide cheap and clean energy which is renewable & sustainable.
Helps control flooding also.

What is the The Gorges Dam?

A dam built on the Yangtze in China at 185m in height and 1.6km in width. Provides cities such as Shanghai with energy but prevent floods.

Name an example of a dam.

Ardnachrusha, Co. Clare

Disadvantages of HEP

Damming the river prevents the fertile alluvium transporting downstream, meaning farmers need to used artifical fertilisers. Much of the Shannon’s volume is diverted to the HEP station which means water flowing downstream is reduced and fish stock are being depleted.

In which stage of the river are deltas found?

They are found in the lower or old stage of the river.

What is a delta?

A triangular or fan-shaped area of land found at the mouth of a river, where it enters a lake or the sea.

Why does the river lose energy at its mouth?

Because it meets the still water of the sea or lake.

What happens when the river loses energy?

The river deposits its load of sediment.

When does a delta form?

When the river’s mouth becomes choked with sediment.

What happens when the river’s mouth becomes blocked by sediment?

The main river splits into smaller channels called distributaries.

What are distributaries?

Small channels that branch off from the main river as it flows through a delta.

What conditions are needed for a delta to form?

The river must deposit a large amount of sediment; the sea must have a small tidal range and weak currents; the sea must be shallow at the river’s mouth.

Name an example of a delta.

Mississippi Delta (USA)

Why doesn’t every river form a delta?

Because some rivers flow into deep seas or areas with strong tides and currents that carry away the sediment.

V-shaped valleys

Youthful stage (Upper)

Meanders

Mature stage (Middle)

Flood plains

Old stage (Lower)

Interlocking spurs

Youthful stage (Upper)

Oxbow lakes

Mature stage (Middle)

Levees

Old stage (Lower)

Waterfalls

Youthful stage (Upper)

Erosion

The river wears the landscape away.

Transportation

The river carried the material it has eroded.

Deposition

The river drops the eroded material it has carried.