1GB2: River Processes And Pressures Flashcards
Abrasion
the process of rocks and pebbles carried by the waves wearing away rocks as they are thrown against cliffs.
Traction
a method of transportation for large stones or boulders in a river
Attrition
this is when rocks that the sea is carrying knock against each other. They break apart to become smaller and more rounded
Solution
The transport of dissolved chemicals
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.
Saltation
pebbles are bounced along the river bed, most commonly near the
source
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.
Suspension
lighter sediment is suspended (carried) within the water, most commonly near the
mouth of the river
What do meanders and oxbow lakes need to form?
A fast moving river
Lots of dirt
Soft land
Where do meanders usually form?
In the lower course of the river on wide floodplains
Why do rivers need to move fast for meanders to form?
To carry dirt and erode the land
What kind of land is needed for meanders to happen?
Soft, easy to erode land
What helps the river bend and form meanders?
High energy (speed) in the river and a lot of sediment
What is the water and sediment load like in the upper course of the river?
Less water and sediment
Why can’t rivers erode as much in the upper course?
Land is harder and more resistant
What happens when a river flows around hard parts of mountains?
It creates interlocking spurs
What shape do valleys tend to have in the upper course of a river?
Steep, v shaped valleys
What can happen if theres a sudden change in geology?
It might create a waterfall
How does a waterfall form?
When a river flows over hard rock and erodes softer rock beneath it, creatina drop
What happens to the softer rock in a waterfall?
It erodes faster than the rock above it
What forms at the base of a waterfall?
A deep pool or river
Can a waterfall move overtime?
Can move upstream as it continues to erode the rock
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
What are deltas?
Areas where a river meets a sea or lake, and the river drops dirt and sand as it slows down
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.
