Unit 1 Case Study: The River Severn (2020)

Question 1

Describe the location of the river severn

Answer 1

It rises near the River Wye on the North-East slopes of Plynlimon, Wales and follows a semi-circular path South to the Bristol Channel and the Atlantic Ocean. It drains an area of 11266 square kilometres and is about 354 km long. It provides a natural border between England and Wales. The source is in the Cambrian Mountains of Wales at 610 metres of elevation

Question 2

How did the storms cause flooding in February?

Answer 2

The 1st week of February brought 3 named storms:
Ciara (7th-8th)
Dennis (15th-16th)
Jorge (28th-29th)
This led to a new highest rainfall monthly total with some places getting 3 times the monthly average

Question 3

How did the permeability of rock and soil cause floods?

Answer 3

If the soil is saturated like in February 2020 due to persistent heavy rainfall, the rain can’t infiltrate the soil and runs straight into the river. This increases discharge and leads to flooding. Soil moisture deficits for the UK had been at 0% for the previous 5 months

Question 4

How did vegetation cover cause flooding?

Answer 4

Where there is complete vegetation cover, the plants will intercept some water and store it so less entres the river. Along the river severn, large areas of former floodplain have had housing built on them so rain flows straight into the river. Areas along all of the river have seen significant deforestation

Question 5

How is heavy and prolonged rainfall a flood trigger?

Answer 5

The storms in February generated 209 mm of rainfall, more than double the expected amount

Question 6

How the the jet stream contribute to flooding?

Answer 6

The changed position of the jet stream, a fast flowing narrow current of air in the high atmosphere which can drive depressions across the Atlantic. In 2020 it was further South than usual so brought a series of low pressure storms to the UK with heavy rainfall

Question 7

How might climate change be contributing to floods?

Answer 7

Between 1998 and 2020 there were 6 of the 10 wettest recorded years. Some believe that climate change is increasing the probability of the UK experiencing more extreme rainfall

Question 8

Impacts of floods: deaths

Answer 8

The most important impact of flooding is deaths. People can be washed away and drowned in muddy waters. Flood waters can also sweep away cars, trees and furniture. People in the water can be hit by these obstructions. On the 25th of February 2020, there was a ;threat to life’ warning for Ironbridge as 40 were evacuated due to fears that river would reach dangerous levels

Question 9

Impact of floods: houses

Answer 9

Floodwater can result in large scale damage to furniture, white goods or the structure of a house. Houses flooded can take a long time to dry out and people have to move out until repairs can be done. Often the water is polluted with sewage from the failed drainage system so clean-up takes longer and disease can spread

Question 10

Impact of floods: famrs

Answer 10

Farm animals can be cut off in fields and drowned by rising flood waters. There is damage to crops and farmland. When farmland is flooded, crops are destroyed and rot in the fields. Planting or sowing of new crops may be delayed or never happens. Prices rise.

Question 11

Impact of floods: factories

Answer 11

In factories, equipment may end up floating around. Damage can be extensive and expensive. Some may be forced to close and never reopen leading to unemployment. In places such as Tewkesbury, water pumping stations may be affected which affects the water supply to thousands of homes. Power stations can be flooded so electricity supplies to homes and businesses may be cut off

Question 12

Impacts of floods: shops

Answer 12

People whose shops are flooded have to dispose of flood-damaged stock and have the cost of re-stocking. In cases such as Upton,some shops were unable to secure flood insurance so have to meet the full costs themselves. Has led to shops closing and not reopening

Question 13

Positive impact of floods

Answer 13

Sediments are deposited on the flooded areas which can add to the fertility of the soils in those areas. Areas of Worcestershire close to the severn and avon have benefitted from this. However farmers have to wait until soil is dry

Question 14

Flood management: dams

Answer 14

Dams can control the amount of discharge in a river. The Clywedog in Wales at the head of the severn was built between 1963 and 1967 to regulate the flow of the river and help prevent flooding downstream. The reservoir behind the dam releases water during droughts and holds back water during heavy rainfall. The volume of rain in February 2020 was in excess of the capacity of the dam and downstream areas

Question 15

Why is building dams controversial?

Answer 15

People in Wales objected to flooding the valleys behind the dam and in 1966 a bomb exploded in the construction site from activists. Recently there was a proposal to build a dam in Shrewsbury to hold back more floodwater

Question 16

Flood management: flood walls

Answer 16

In the sever, they have been used as a temporary flood barrier that can be installed quickly when floods are forecasts. Raising the riveranks helps contain the river in its channel to prevent flooding of local homes. These are common in Shrewsbury, Bewdley and Ironbridge. The Environment Agency deploys them when there is a flood warning. They are not as robust as more permanent structures so they can be overwhelmed or destroyed in a big flood such as in Ironbridge 2020

Question 17

Flood management: artificial levees

Answer 17

Can be built along riverbanks to raise them to a level where the river might not burst its banks. They are expensive and can spoil the look of the river. In Worcester, flood embankments have been built because they are cheaper but they takes up a lot of space and may only increase the speed of the water. This may just move the floodwaters further down the river

Question 18

Flood management: deepening and widening

Answer 18

This is done so water can travel faster. May just move the flood downstream

Question 19

Flood management: soft engineering

Answer 19

Includes planting trees near the river to achieve more interception of rainfall and lower discharge. This is quite cheap and long-term. South of Worcester the river is allowed to spill over the floodplain to reduce the danger to built-up areas. There is conflict between developers wanting to build the many new houses needed on the cheap land of the floodplain and conservationists who know that building on floodplains adds to flood issues.