Geography Rivers and Coasts Paper 1.

Describe how waves form.

1. wind blowing over the ocean creates friction with the water surface causing ripples to form.

2. Faster moving ripples merge with slower ones. Waves become bigger and more organised.

3. The longer the waves travel for, the larger and more organised they become

What is backwash?

movement of the wave down the beach

What is swash?

movement of the wave up the beach

Describe the features of a constructive wave.

• wave crests are far apart

• wave spills forward

• gentle sloping wave front

• strong swash and weak backwash

• results in gentle beach

Describe the features of a destructive wave.

• wave crests are close together

• steep wave front

• wave plunges downwards

• strong backwash which pulls pebbles and sand out to sea

• results in steep beach

What is weathering?

The breaking down of rocks by mechanical, chemical or biological processes.

What is freeze thaw action?

• mechanical weathering

• where rain fills up in cracks in rocks, freezes overnight and expands which pushes the crack outwards

What is mechanical weathering?

The break up of rocks by physical force.

e.g. freeze thaw and biological weathering

What is biological weathering?

weathering when living things like animals and plants burrow into a crack which eventually weakens the structure.

What is chemical weathering?

Where rainwater which contains carbon dioxide, reacts with the calcium carbonate in rocks such as limestone and chalk. This dissolves and is washed away in the solution, weakening the rock.

What are the types of mass movement?

• mudflows

• rockfalls

• landslides

• rotational slip

What is rockfall?

• fragments of rock break away from the cliff face often due to freeze thaw weathering. 

• piles of rock called scree form at the bottom

What is a landslide?

Where blocks of rock slide downhill because the bedding of the rock sloops downwards and makes it more likely that large blocks will shear out.

What is a mudflow?

• soil or weak rock becomes saturated

• occurs on slopes over 10 degrees tilt

• rapid sudden movement occurs when there is not enough vegetation to hold the soil in place.

What is rotational slip?

• occasional rapid movement of a mass of earth or rock sliding along a concave plane. They can occur over periods of heavy rain, when the water saturates overlaying rock, making it heavy and liable to slide.

What do processes end in?

ION

e.g. 

erosion

abrasion

solution

What are the processes or erosion?

• hydraulic action

• abrasion

• attrition

• solution

What are the processes of transportation?

• traction

• saltation

• suspension

• solution

What is erosion?

The process of seawater wearing away land

What is hydraulic action?

• type of errosion

• The power of the waves as they smash against the cliff

• trapped air is forced to make holes in the rock

• this forces the rock to eventually break apart

What is corrasion?(abrasion)

type of erosion

fragments of rock, pebble and sand are picked up by waves and hurled at cliffs, acting is sandpaper

What is attrition?(it doesn’t wear the cliff down)

type of erosion

Where rocks and pebbles under the water knock against each other continuously, which chips fragments off.

What is solution?(corrasion)

type of erosion

acids in the seawater erode rock.

What is suspension?

type of transportation

particles are suspended in the flow of the water

What is solution?

• type of transportation

• rocks are being transported as dissolved chemicals, often from chalk

What is traction?

Type of transportation

large pebbles are rolled along the seabed by currents

What is saltation?

Type of transportation

Currents lift up pebbles which bounce along seabed.

What is deposition?

Where sediment is dropped due to less wave energy.

What is long shore drift (LSD)

1. pebble moves up the beach at an angle due to swash

2. backwash carries the pebble down the beach at a straight line

3. this happens continuously at the general direction of the prevailing wind. 

How are headlands and bays formed?

• they are formed through differential erosion of hard and soft rock over time.

• Also, headlands receive wave energy from all angles and therefore, the most energy because of the wave refractions

Define Landform

A feature of a landscape e.g. cliff

Define differential erosion

rocks erode at different rates

What is a discordant coastline?

Alternating bands of lots of different rock types (hard and soft) along a coastline

What is a concordant coastline?

Rocks are parallel to the wave front and therefore rates of erosion are similar.

What is a beach?

A zone of deposited material that extends from the low waterline to the limit of storm waves.

What are the features of a sandy beach?

• sheltered bays

• strong swash

• shallower beach

What are the features of a pebble beach?

• high energy environment

• steeper beach

Explain the formation of a sand dune.

1. embryo dunes form around obsticals e.g. rocks

2. dunes develop and are stabilised by marram grass

3. decomposing vegetation makes sand more fertile which increases range of plans

4. dune slacks can form in depressions ( ponds)

What causes formation of sand dunes?

1. a high tidal range

2. marram grass and other specialist plants

3. a large supply of sand

4. obstacles on the strand line

5. a strong onshore breeze

6. mainly constructive waves

What is a spit?

A depositional landform formed when sediment extends from the shore out to sea. It usually has curved ends because of winds and currents.

Describe the features of a spit.

Describe the features of a bar.

Describe the features of a tombolo.

What is hard engineering and it’s features?

Using concrete and large artificial structures to defend land against natural erosion processes.

• expensive

• long term

• concrete steel or wood

• visual pollution

What is a sea wall?

• hard engineering

• concrete or rock barrier built against the sea to reduce erosion rates

• Adv : highly effective, sense of security and long lasting

• Dis : prevents LSD

What is a Groyne?

• Hard engineering

• Timber or rock structures out to sea that trap sediment transported by LSD and slow wave erosion

• Adv : cheap and sustainable

• Dis : increased erosion by sediment and unnatural look

What is rock armour?

• Piles of rock (usually granite) placed at foot of cliff to absorb and disperse sea energy

• Adv : cheap, effective and look natural

• Dis: can be shifted by waves and if done wrong could look unnatural

What are gabions?

• Wire cages filled with belled that last 20-30 years

• Adv : Cheap, effective and improve drainage

• Dis : ugly and poor quality

What is soft engineering?

A sustainable and natural approach to managing coasts

What is beach nourishment?

• Soft engineering

• Sand is pumped into an existing beach to build it up

• Adv : blends in and can appeal to tourists

• Dis : has to be constantly replaces and sand has to come from somewhere else.

What is reprofiling?

• Soft engineering

• Where sediment like sand is redistributed from the lower part of the beach to the upper part

• Adv : reduces energy of waves, Cheap and simple

• Dis : only effective when wave energy is low and needs to be repeated continuously

What is Dune regeneration?

• Soft engineering

• Where marram grass is planted on sand dunes which stabilises them and helps trap sand to build them up.

• Adv : cheap and looks natura

• Dis : Could be damaged by storm waves and areas must be zoned off from public which could be unpopular with locals and tourists.

What is managed retreat and when is it used?

Managed retreat is where cliff erosion is allowed to take place and no protective measures are put in place.

This is used when:

• land is low value

• low budget

• desire for a new habitat

• defending coastlines are difficult

How are oxbow lakes formed?

1. Erosion erodes the neck of the meander

2. water starts to take the shortest route as the meanders neck starts to be cut through

3. further deposition occurs in the stagnant water as over time it will be filled with organic water which turns into an oxbow lake

What us a drainage basin?

An area of land where all the built up surface water eventually ends up at the same point like a river, lake or ocean.

What is a source?

• also known as headwater

• the farthest place in the river or stream from its estuary or mouth

What is drainage density?

• the total number of streams in a drainage basin

• the greater the number of streams in an area the higher the drainage density is

What is a tributary?

a small stream flowing into a larger stream or river or lake

What is a river channel?

The channel or groove where the river flows. v - shaped with banks

What is a delta?

• NOT all rivers have these

• landforms created by deposition or sediment that is carried by a river as the flow leaves it’s mouth

What is a river mouth?

Where the river stops flowing on land and meets the sea

What is a watershed?

This marks the invisible boundary of high ground that separates one drainage basin from another

What is a meander?

Where the river bends

What is a confluence?

Where two rivers combine together to form one larger river in a single channel of water.

What is the long profile of a river?

The long profile shows the gradient of a river as it journeys from source to mouth.

What occurs in the upper course of a river?

• freeze thaw weathering to create v- shaped valleys

• vertical erosion

• hydraulic action

• traction for transportation

• waterfalls, rapids

• steep, rocky, narrow, turbulent

• source of river is here

• interlocking spurs

What occurs in the middle course of a river?

• hilly relief

• greater discharge leads to less vertical erosion and more lateral erosion

• erosion is mainly attrition and abrasion

• transportation is mainly suspension

• deposition increases and mainly happens in meanders

• oxbow lakes

• pools and ripples

What occurs in the lower course of a river?

• flat relief

• little erosion in the lower course. (some lateral)

• transportation is solution and suspension

• levees (deposited sediment that help to protect the river from flooding)

• floodplains

• estuaries

What is discharge?

The volume of water passing a given point on the river.

What is a river cross profile?

A river’s cross profile changes from steep and narrow near the source to wide and flat near the mouth as erosion and deposition shape the valley

Describe the cross profile in the upper course.

The river has a V-shaped valley with steep sides and a narrow channel. Vertical erosion is dominant as the river cuts downwards

Describe the cross profile in the middle course.

The valley becomes wider with gentler slopes, and the river channel deepens and widens due to increased lateral erosion and higher discharge

Describe the cross profile in the lower course.

The river has a wide and flat floodplain where deposition dominates, resulting in lots of energy being lost at the mouth.

What are the main types of erosion that erode the riverbed and banks resulting in a changing cross profile?

Hydraulic action and abrasion

What is the difference between vertical and lateral erosion?

How are waterfalls formed?

Describe and explain the features of a waterfall.

• The overhang is formed by soft rock undercutting hard rock which keeps happening until the hard rock is no longer supported and collapses

• The repeat of this process creates a gorge

• additionally, abrasion and hydraulic action form a plunge pool

What are the physical factors that increase flood risk?

• torrential storms - they can cause flash floods and flood river basins

• highlands have steep slopes so encourage rapid water transfer to water channels

• impermeable rocks like granite and clay mean water will be more likely to flow into a river channel which makes flooding more likely

• snow formed in winter is stored in snow packs in high relief which means if it melts quickly can overwhelm river channels

What are the human factors that increase flood risk?

• climate change impacting things like snow melting

• deforestation - lots of water is stored by forests and woodlands. This means when it is cut down they are available to be transferred to river channels.

What is a storm/flood hydrograph and what is its use.

A flood hydrograph shows the relationship between rainfall and river discharge during and after a storm. It helps geographers understand why some rivers flood quickly while others respond more slowly.

What is channel enlargement.

• Hard engineering

• dredges the river to increase river capacity and increase discharge.

What is channel straightening?

• hard engineering

• speeds up water flow in a river

What is land use zoning and floodplain zoning?

• land use - NEW developments constructed away from areas of high flood risk areas

• floodplain - planning entire communities in a cost effective way meaning if the river floods it will only flood low value areas of land e.g. parks.

Evaluate floodplain zoning

+ high cost effectiveness

+ requires little maintenance

- limits urban expansion

- hard to apply to towns and cities that are already developed

What does afforestation do in terms of helping reduce flood risk?

• reduces soil erosion

• takes up water

• coniferous environments would create acidic soil and low biodiversity forests

• takes several years to grow