River landforms and Coastal landforms, River flooding

How are waterfalls formed?

How are waterfalls formed?

1. There’s a horizontal band of more resistant rock positioned over exposed, less resistant rock.

2. Soft rock is eroded quicker than hard rock (hydraulic action) causing undercutting of the hard rock.

3. The hard rock overhangs until it can no longer support its own weight and collapses.

4. Abrasion and hydraulic action vertically erode the soft rock to create a plunge pool.

5. The process of undercutting and collapse is repeated, resulting in the waterfall’s retreat upstream and the plunge pool getting deeper.

6. A steep-sided valley known as a gorge is left where the waterfall once was before it retreated.

How are V-shaped valleys and interlocking spurs formed?

1. The upper course of a river doesn’t have enough energy for suspension of particle and instead transports it using traction or saltation.

2. This results in vertical erosion of the riverbed.

3. This creates a V-shaped valley.

4. If there are areas of hard rock which are harder then the river will bend around them, creating interlocking spurs.

How are meanders formed?

• In the middle course, the river gains more water and therefore more energy.

• Material can be carried in suspension and this material laterally erodes the river banks, widening the river.

• When river flow is stronger on one side, most of the water is pushed to that side, causing increased speed due to less friction.

• Lateral erosion via abrasion and hydraulic action on the outside bend causes undercutting of the river bank to form a river cliff.

• The inside bend has less water and thus increased friction, so the water slows down, loses energy and deposits material. The build-up of deposited sediment is known as a slip-off slope.

How are oxbow lakes formed?

• Due to continued erosion of the outside of a meander and deposition on the inside, the ‘neck’ of land within the meander is narrowed.

• Over time, or if there’s a very high discharge (during a flood), the river will cut across the neck to take a new, straighter and shorter route.

• Deposition occurs to cut of the original meander, leaving an oxbow lake.

How are floodplains formed?

• In a wide, flat valley (interlocking spurs may have been removed by erosion), a river floods

• The water which has flowed into the valley is fastest directly next to the river, but the further it travels, the more energy it loses due to friction with the ground and vegetation, so any sediment it was carrying is deposited.

• This leaves a layer of sediment over the valley.

• After multiple floods, the floodplain is created, which is wide, flat, and very fertile due to the nutrients contained in the deposited sediment.

How are levees formed?

• Levees occur in the lower course of a river where there is an increase in volume of water flowing downstream and it floods.

• The water which has overflowed loses more energy as it travels further away from the river.

• This means that the largest material is deposited first on the sides of the river banks whereas smaller material is carried further.

• The larger sediment builds up on the banks of the river over multiple floods

• This creates a natural embankment on the bank of the river, meaning that the channel can carry more water.

What is an estuary?

• Where the river meets the sea

• The river here is tidal

• When there is less water, the river deposits silt to form mudflats.

Where is the River Tees?

• North England

• Source is in the Pennines ~893m asl.

• Flows east

• Mouth joins the North Sea

Where is the River Parrett?

• South west England

• Source in hills in Dorset ~179m asl.

• Flows through Dorset and Somerset

• Mouth meets the Bristol Channel

Factors that have affected the River Tees

• Geology: contributed to the formation of the High Force waterfall. Its source is in an area of limestone, which is soluble and has contributed to the formation of a gentle v-shaped valley. Downstream, the geology changes to be more resistant Whin Sill which is far more resistant and the valley becomes more vertical.

• Topography: Source in Pennines, upland area, a lot of rainfall as the moorland is easily saturated

• Humans: In 1810, Mondal loop cut off to straighten river for ships. Waste from ships narrowed river around Teesside.

Distinctive land area

Landscape

High land with steep relief

Upland

Low-lying land with gentle relief

Lowland

Landscapes formed by glaciers

Glacial

Landscapes shaped by sea erosion and weathering

Coastal

Landscapes shaped by rivers

Fluvial

Uncultivated grassland

Moorland

Northern and Western regions of the UK

Typical location of upland areas

Resistant rocks like slate, granite, and limestone

Rock composition of upland areas

Cool and wet climate with thin soils

Climate of upland areas

Sheep Farming, Quarrying, Tourism

Land Usage of Upland Areas

S and E of the UK

Location of Lowland Areas

Soft Rocks such as Chalk, Clay, Sandstone

Composition of Lowland Areas

Warmer, Drier Climate with Fertile Soil, Grasslands, Deciduous Forests

Climate in Lowland Areas

Quarrying, Tourism, Dairy, Arable Farming, Urban Areas

Land Use in Lowland Areas

Upland Areas in the N and W of England

Location of Glaciated Regions

Where a River Begins

Source

Where a River Meets the Sea or an Outlet

Mouth

Tributaries

Smaller Rivers Joining Larger River

Area of Land Draining into a Common Outlet

Drainage Basin

Boundary between two drainage basins

Watershed

Meeting point of two streams or rivers

Confluence

All streams/rivers in one drainage basin

Network

Power of waves causing rock cracks

Hydraulic action

Pebbles grinding on rock platform

Abrasion

Sea water dissolving rocks

Corrosion/solution

Rocks breaking apart by knocking

Attrition

Rolling of pebbles and material on seabed

Traction

Bouncing of shingle or sand grains on seabed

Saltation

Suspension of small particles in water

Suspension

Minerals dissolved in rock and carried in flow

Solution

Sea loses energy, drops material carried

Deposition

Distance wind blows to create sea waves

Fetch

Flow of water up beach as wave breaks

Swash

Flow of water back to sea after wave breaks

Backwash

Flat, low energy beach; Swash > Backwash

Constructive waves

High energy, breaks downwards; Strong backwash

Destructive waves

Conditions for creating waves

Constructive waves in calm, destructive in stormy

6-9 waves per minute

Frequency of constructive waves

10-14 waves per minute

Frequency of destructive waves

Waves approaching at an angle to the coast due to the prevailing winds. Swash carries material up at an angle. Backwash is perpendicular to the coast (gravity).

Long Shore Drift

Southwesternly winds (blowing northeast).

Prevailing Wind in the UK

Where and why does deposition occur along the coast?

• Sheltered bays

• Shallow water

• Groynes on the beach.

A section of hard rock jutting out into the sea.

Headland

Bay

Areas where the soft rock has eroded away.

How are headlands and bays formed?

1. Sea attacks a section of coast with alternating bands of soft rock.

2. This leaves a section of land jutting out into the sea called a headland.

3. The areas where softer rock has eroded away are called bays.

How is a cave formed?

Caves occur when waves force their way into cracks in the cliff face. Hydraulic action and abrasion are the predominant erosion processes.

How is an arch formed?

If the cave is in a headland, it may eventually erode through to the other side.

How is a stack formed?

The base of the arch becomes wider through erosion until its roof collapses into the sea, leaving a stack.

How is a stump formed?

The stack will be attacked until it is undercut, collapses, and forms a stump.

Subaerial processes

Processes occurring above the waterline

Freeze thaw weathering

Water filling cracks in rock and expanding when it freezes

Salt cracking

Salt crystals accumulating in rock cracks and causing shattering

Biological weathering

Roots growing into cracks, spreading, and breaking rocks

Chemical weathering

Chalk and limestone reacting with acidic water, forming washable substance

Bedding planes

Horizontal cracks in rock

Joints

Vertical cracks in rock

Landslide

Sudden hillside collapse triggered by earthquake or erosion

Rock fall

Sudden rock collapse from cliff or steep slope

Slumping

Gradual hillside collapse due to saturation and soft rock sliding down

What type of rock are slumping cliffs made of?

Young sedimentary rock that is unconsolidated as the sediment is not 'glued' together well

What is a wave cut platform?

A wide gently sloping surface found at the foot of the cliff

How is a wave cut platform formed?

A wave cut notch first forms by erosion with abrasion and hydraulic action. This undercuts the cliff and the cliff overhangs the notch. The fallen rocks create a wave cut platform by attrition which smoothens it

How are meanders formed?

• In a straight river, riffles (shallow with deposition) and channel pools (deep with erosion) will form.

• This results in areas of slow and fast water movement.

Helicoidal flow

A corkscrew-like flow of water moves material from the outside of one meander bend to the inside of the next one

Slip-off slope

On the inside of a meander bend, where the river flow is slower, material is deposited and there is more friction, resulting in a slip-off slope

What is a floodplain?

A floodplain is a wide, flat area of land on either side of a river and is covered in times of a flood

How does the National Trust Centre impact Studland Bay?

Pros: Big social input to the area, lots of revenue. Cons: Affects the beauty of the area, considered an eyesore. However: Planting trees, color scheme decided on, uses hot oil to prevent cloud formation.

Describe the journey from precipitation to groundwater of a drainage basin

Precipitation - Interception - Surface storage - Infiltration - Soil moisture - Percolation - Groundwater.

What are the three methods of movement in a drainage basin

Surface runoff, transpiration, through flow, groundwater flow, evaporation.

Zone of saturation

The point at which no more water can fill the pores in the rock.

Water table

The top of the zone of saturation.

Features of the Dorset Coast

• Old Harry Rocks: Collapsed arch, cave, stack. - Swanage: Discordant bay of limestone and clay, Swanage Bay, Ballard Point, Durlston Head. - Chesil Beach: Spit, The Fleet Lagoon.

What processes lead to the formation of a river?

Formation of a River

What is the term for a U-shaped body of water that forms when a meander is cut off from the main river flow?

Oxbow Lake

Flood management strategies

• Hard engineering

• Soft engineering

• Forecasting and education

• Planning and building design

Coastal Erosion

What is the process of land loss along coastlines due to natural forces like waves and currents?

What are long, narrow islands parallel to the mainland that protect the coast from the full force of storm waves?

Barrier Islands