1GB2: River Processes And Pressures Flashcards by Tansi Jakhar

Abrasion

the process of rocks and pebbles carried by the waves wearing away rocks as they are thrown against cliffs.

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Traction

a method of transportation for large stones or boulders in a river

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Attrition

this is when rocks that the sea is carrying knock against each other. They break apart to become smaller and more rounded

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Solution

The transport of dissolved chemicals

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Hydraulic action

This is the sheer power of the water as it smashes against the river banks. Air becomes trapped in the cracks of the river bank and bed, and causes the rock to break apart.

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Saltation

pebbles are bounced along the river bed, most commonly near the
source

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Corrosion

a process of chemical erosion. Rocks or stones can be eroded as water gets into cracks and holes and dissolves the rock through chemical changes. This process can occur with acid rain.

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Suspension

lighter sediment is suspended (carried) within the water, most commonly near the
mouth of the river

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What do meanders and oxbow lakes need to form?

A fast moving river
Lots of dirt
Soft land

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Where do meanders usually form?

In the lower course of the river on wide floodplains

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Why do rivers need to move fast for meanders to form?

To carry dirt and erode the land

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What kind of land is needed for meanders to happen?

Soft, easy to erode land

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What helps the river bend and form meanders?

High energy (speed) in the river and a lot of sediment

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What is the water and sediment load like in the upper course of the river?

Less water and sediment

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Why can’t rivers erode as much in the upper course?

Land is harder and more resistant

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What happens when a river flows around hard parts of mountains?

It creates interlocking spurs

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What shape do valleys tend to have in the upper course of a river?

Steep, v shaped valleys

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What can happen if theres a sudden change in geology?

It might create a waterfall

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How does a waterfall form?

When a river flows over hard rock and erodes softer rock beneath it, creatina drop

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What happens to the softer rock in a waterfall?

It erodes faster than the rock above it

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What forms at the base of a waterfall?

A deep pool or river

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Can a waterfall move overtime?

Can move upstream as it continues to erode the rock

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What makes the waterfall pool deep?

Water hits the bottom with a great force, eroding the rock and making the area deeper overtime, this digs into the ground

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What are deltas?

Areas where a river meets a sea or lake, and the river drops dirt and sand as it slows down

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What happens on the inner side of a meander?

The water moves slower, so it drops dirt, creating a gentle bank

What are floodplains?

Floodplains are flat lands next to rivers, made when floods drop dirt and sand

What is deposition?

Deposition is when the river slows down and drops the dirt and sand it’s carrying

What are levees?

Levees are mounds of dirt along riverbanks formed by floodwater dropping dirt

Where do deltas form?

Deltas form when a river meets a sea or lake

Why do rivers drop dirt and sand in deltas?

Because the river slows down as it reaches the sea or lake

What happens to big chunks of dirt in deltas?

They are dropped first, smaller bits are dropped later

What are meanders?

Curves in the rivers path

Where is the water fastest in a meander?

The water is fastest on the outside of the curve, eroding the bank

What haooens on the inside of the meander?

The water is slower, so it drops dirt, forming a gentle bank

What causes a floodplain to form?

Erosion by the river and the deposition of dirt and sand during floods

How do floodplains get higher overtime?

Floods deposit more dirt and sand on the land, raising its height

What is depoisition in a river?

Deposition is when a river drops the dirt and sand it’s carrying, usually when it slows down

Why do levees form?

Levees form when a river floods, and the water drops dirt along the banks

How do levees get taller?

Each time the river floods, it deposits more dirt, making the levees higher overtime

Where does the River Severn start and end?

Starts in wales and ends in the bristol channel

What is the river severn?

Longest river in the UK

What is lateral erosion

Sideways erosion

What is the gradient like in the upper, middle and lower course of the river?

Steep Less steep Shallow gradient

What is the discharge like in the upper, middle and lower course of the river?

Small Large Very large

What is the depth like in the upper, middle and lower course of the river?

Shallow Deeper Deep

What is the channel like in the upper, middle and lower course of the river?

Narrow, steep sides Flat, steep sides Flat floor, gently sloping sides

What is the velocity like in the upper, middle and lower course of the river?

Quite fast Fast Very fast

What is the valley shape like in the upper, middle and lower course of the river?

Steep sides Flat steep sides Flat gently sloping sides

What is the features like in the upper, middle and lower course of the river?

Waterfalls, interlocking spurs Meanders, floodplain Meanders, floodplain, levees, ox bow lakes

How does discharge change over the river course?

Increases downstream

How does occupied channel width change over the river course?

Increases downstream

How does channel depth change over the river course?

Increases downstream

How does load quantity change over the river course?

Increases downstream

How does load particle size change over the river course?

Decrease downstream

How does channel bed roughness change over the river course?

Decreases downstream

How does slope angle (gradient) change over the river course?

Decrease downstream

Which precipitation process would lead to a steeper hydrograph?

Large amounts of rainfall Heavy rainstoems

Which geology process would lead to a steeper hydrograph?

Impermeable rocks Cant absorb water

Which soil process would lead to a steeper hydrograph?

Frozen soil Soil saturated by previous rainfall More run-off

Which slopes and soil depth process would lead to a steeper hydrograph?

Steep slopes Thin soils Rapid run-off

Which vegetation process would lead to a steeper hydrograph?

Little vegetation Less barriers from rainfall More run-off

Which towns and cities process would lead to a steeper hydrograph?

Urban surfaces Roads and roofs Impermeable Run-off

Which precipitation process would lead to a flatter hydrograph?

Small amounts of gentle rainfall

Which geology process would lead to a flatter hydrograph?

Permeable rocks Can absorb/store water Sandstone

Which soil process would lead to a flatter hydrograph?

Dry soil Can absorb more water

Which slopes and soil depth process would lead to a flatter hydrograph?

Gentle slopes Deep soils Slower run-off

Which vegetation process would lead to a flatter hydrograph?

Woodland intercepts Slower run off

Which towns and cities process would lead to a flatter hydrograph?

Rural land use Permeable surfaces Less run-off

What is a hydrograph and what does it tell you?

a graph that depicts how water discharge varies over time at a specific point in a river or channel

What are antecedent conditions?

wet conditions before a storm cause the ground to become saturated

What physical factors made the River Severn prone to flooding?

Steep welsh mountains Easy run off Lots of steep v shaped valleys

What human factors made the River Severn prone to flooding?

Lots of bridging point settlements A lot of damage was done in Tewksbury and Shrewsbury

What increased risks made the River Severn prone to flooding?

More urban development - impermeable surface run off

What hard engineering can engineers construct to stop the Thames from flooding?

Flood walls Embankments Flood barriers

What soft engineering can engineers construct to stop the Thames from flooding?

Flood plain retention River channel resoration

What are flood walls?

High walls to increase the capacity of the rivers Cheap Disperse water quickly - but it increases downstream flood risk

What are embankments?

Walls increasing river capacity further from channel Tend to be made of earth/grass - blends in with environment Increase flood risk downstream Expensive

What are flood barriers?

Permanent Expensive Regular maintenance Demountable barriers are put up/down but can be quite ugly and very specific in location - not enough time to put up

What is a flood plain retention?

By retaining water, floodplains can buffer the effects of heavy rainfall and in this way protect economic activities and communities further downstream from flood damage

What is river channel restoration?

River restoration refers to a large variety of ecological, physical, spatial and management measures and practices. These are aimed at restoring the natural state and functioning of the river system in support of biodiversity, recreation, flood management and landscape development.