The River Itchen Case Study

Question 1

Name case study: river catchment at a local scale

Answer 1

The River Itchen in Winchester
- 28 miles long

Hampshire pop projected to grow 4.8% in next decade. Therefore increased pressure on water environment

Question 2

What is the precipitation like at the drainage basin?

Answer 2

February to September is steady (60mm), October to January is higher but also steady (10mm). Mean annual precipitation c.900mm

Question 3

What is the Topography like at the drainage basin?

Answer 3

Gently undulations - river has a low altitude with a high point of 290m
Low lying - therefore resulting in a number of flood plains

Question 4

What is the vegetation like at the drainage basin?

Answer 4

Some specific woodland
Mostly grassland

Question 5

What is the rural land use like at the drainage basin?

Answer 5

Predominant arable
- 1,110sqkm of the area is used for farming
- 62% of the catchment area

Question 6

What is the urban land use like at the drainage basin?

Answer 6

1. Predominant residential
   - the urban area, such as Southampton has a population of 725,000. Due to this it causes high rates of abstraction and pollution
2. Negligible industry

Question 7

What is the soil like at the drainage basin?

Answer 7

1. Loamy, some sandy (porous)
2. In the down catchment of the river, the chalk is covered by a well-drained calcareous, flinty and silty soils.

Question 8

What is the rocks like at the drainage basin?

Answer 8

1. Chalk (porous ) - chalk covers 80 - 90 % of the catchment.

Question 9

What is the groundwater store like at the drainage basin?

Answer 9

1. Significant aquifer
2. Classified as being seriously water stresses, largely due to comparatively low levels of rainfall combined with particularly high levels of water being abstracted from the ground/ and or rivers

Question 10

What is the river like at the drainage basin?

Answer 10

1. Itchen, 42km, two tributaries (Candover Stream, Cheriton Stream)
2. Elongated basin as there are very few tributaries flowing into the river.
3. Low drainage density

Question 11

What is the flooding events like at the drainage basin?

Answer 11

1. Last major floods in winter 2014
2. The area is surrounded by tarmac (urban) resulting in water infiltration and percolation not to happen. As a result, chances of flooding increase.

Question 12

What are the human disruptions to this drainage basin water cycle?

Answer 12

1. Several pumping stations along the river course which reduces the volume of
   water in the river
2. Agricultural land use- Crops increase interception storage and also remove water
   through transpiration.

Question 13

What are the physical factors of the River Itchen Drainage basin?

Answer 13

Flat land gradient- highest altitude is 120m. This reduces surface run-off as the
water has time to infiltrate the soil.
•Permeable Chalk rocks
•High precipitation in January and February means there is a higher volume of flow
in these months.
•The drainage basin has an area of 400km squared. This is quite a large area
meaning there is a greater volume of inputs, however there is also more chance of the water being infiltrated in to the soil or intercepted by vegetation due to this large area.

Question 14

What are reasons for differences in the river catchment between rural areas upstream and urban areas downstream?

Answer 14

Reasons for differences:
•More rural land use in Easton compared to Highbridge so the water will reach the
river quicker in Highbridge resulting in a greater volume of flow.
•At Highbridge more tributaries have joined the river which means there is a higher
drainage density that is able to flow into the River Itchen and increase its flow. •At Easton the drainage basin is wider so the water takes longer to reach the river
channel as the extremities are further away, where as at Highbridge the river basin is more narrow and so the extremities are closer, therefore increasing the flow of the river

Question 15

What were the social, environmental and economical impacts of the 2014 flood?

Answer 15

1. Environmental
   - sewage water contaminated the flood water and therfore it was going into peoples houses
   - sediment was displaced
   - trees fell
2. Economic
   - Cost Hampshire County Council £68.5 million overall for repairs, long term and short term management
   - council spent £1.6 million of dense repairs
   - disruption to railway
   - spent £160,000 on damage to council houses
   - lesiure park temporarily closed
   - insurance costs
3. Social
   - homes flooded, possessions destroyed
   - 50,000 people without power
   - Disruption to education, schools and colleges temporary closes
   - disruption to roads: North walls and Park Avenue were temporarily closed

Question 16

What ere the short term management strategies in Winchester?

Answer 16

1. The environment agency are considering permanent barriers and to upgrade the sluice.
2. An artificial stream was made in Easton to reduce the discharge of water in the river Itchen through Winchester.
3. 2 High volume pumps that pumped 84,000 litres of water an hour, help from the involvement of the fire service – Short term management strategy
4. Residents were evacuated and temporarily re-homed during the floods. Sand bags were issued to protect houses at risk. Short term.
5. 70ft barrier across park avenue – short term management strategy

Question 17

What ere the long term management strategies in Winchester?

Answer 17

1. A new wall barrier and sluice gates in park avenue which control flood levels
2. Planning controls, to make areas at risk lower value so that in the long term less people will be affected
3. Hampshire county council spent £1.6million on flood defence repairs and Winchester city council spent £160k on repairs to council houses.
4. Winchester county council have set up a repair and renew grant scheme in the long term so residents affected by floods can claim £5,000
5. 2014 training exercise with a 20m flood barrier as a action plan to mitigate effects of future floods.

Question 18

Brief evaluation of the effectiveness and long term management strategies in Winchester?

Answer 18

Leading up to the event of the flood the management strategies in place were minimal and non effective. However during the floods the fire service along with flood management service acted fast to prevent any further impacts to the City centre. The council responded well to the flood by implementing planning controls as well as sluice gates to control flood levels and reduce economic impacts from future floods. Due to the previous floods, better management and mitigation strategies have been put in place in order to ensure effects aren’t as serious next time.