Case Study: Pickering Beck Flashcards
What is Pickering Beck?
A river in North Yorkshire
When does the beck flood in particular?
In the summer, flash flooding
Which government scheme was piloted in the town?
‘Slowing the Flow’
How much did the 2007 flood cost in damage?
£7 million
How many times was the town flooded between 1999 and 2007?
4
How far does the beck run for?
29km
How does the local relief affect flooding?
The drainage basin has steep relief in the hills of the North York Moors, decreasing time taken to reach the river
How does the vegetation at Pickering Beck affect flooding?
Largely moorland shrubs and heather grow in peat bogs which can soak up water preventing runoff and further flooding.
- If water is redirected for agriculture or forestry, peat dries out
How does the geology affect flooding?
It consists of Gritstone and Limestone (permeable + porous) allowing water to flow through.
Soil is also soft and sandy, so permeable, slowing lag time
Which National Park is the beck located in?
The North York Moors
What is diffuse pollution?
the release of potential pollutants (such as nutrients, pesticides, faecal bacteria, or chemicals) from a range of activities that, individually, may have no effect on the water environment, but, at the scale of a catchment, can have a significant effect are lost from the land into local rivers, groundwater, etc.
What are some examples of diffuse pollution?
- Fertilisers/ pesticides spread at wrong time / too close to a ditch, river, wetland coastal water, etc
- Cultivating too close to a watercourse - removing the buffer strip increases risk of soil loss or field runoff getting straight into watercourses
How have farming practices impacted the river + its water quality?
Farming has lead to diffuse pollution, lowering the water quality
Why is the river prone to flooding?
Due to the steep sided valley that the water runs off into the beck
What was adopted to mange flooding?
A land management technique instead of hard defences
What was constructed at Newtondale?
A large low-level bund to hold/store up to 120,000m3 of water in flood events
How has the town impacted flooding?
Impermeable surface increase run off rates
What was planted around the river catchment?
19ha of hydrophilic plant such as alder and willow trees to create a natural barrier to flood flows
What was constructed at the river catchment?
Large woody debris damns, and natural gullies to help water drain from moorlands into forests
Why were no-burn zones established?
As burning has the potential to speed up run off by lowering interception and promoting hydrophobic soil conditions which reduce the river change as it becomes full of debris
What has been created in terms of no burn zones?
A 10 metre wide buffer zone along the main watercourse therefore vegetation remains (preventing soil erosion), + interception remains (decreasing flooding risk)
How can rainfall in Pickering Beck increase chance of flooding?
- Rainfall in the area is heavy and hydrograph flashy.
- Peak discharge fluctuates as heavy rainfall can result in precipitation arriving too quickly to infiltrate the soil.
- this increases surface run-off leading to water reaching the channel quicker resulting in a greater risk of flooding
How many Large Woody Debris Dams have been constructed in Pickering Beck catchment?
129
How many heather bale dams have been constructed?
187
What are the main land uses in the river catchment area? (4)
Arable crops
Improved grassland
Heather Moorland
Forestry and woodland
How much farm woodland has been planted?
15 ha
How much did ‘Slowing the flow cost’
£3.2 million
What has pastoral farming led to?
Over grazing
What is over-grazing?
Animal eat too much of the vegetation
What does loss of vegetation do?
Removes a water store as it decreases interception of water and INCREASES run off reducing the lag time
How does trampling link to erosion?
It churns up the soil making it easier to erode and be washed away
How does trampling link to compacting?
It compacts the soil making it more impermeable and reduces infiltration rates
What has drainage caused?
it has reduced catchment’s capacity, decreasing lag time making the hydrograph more flashy
What is the size of the drainage basin?
68km2
What do the woody debris damns do?
Increase flood storage by rising water levels and slowing the water
What are low levels bunds?
Banks
What have moorland drains been blocked with?
Heather bales
What does blocking drains do?
Encourages natural storage and reduce fast water flowing to river
What does Newtondale bund do?
Lowers the flood peak downstream therefore reduces the flood risk
Why does Pickering Beck have a flashy hydrograph? (3)
- Very hilly so water can’t infiltrate - gets filled quickly by the relief rainfall.
- High No of tributaries
- Lag time is short as precipitation reaches river quickly
