Pickering Beck Local Scale Case Study Flashcards
Where is the beck
Pickering beck runs for 18 miles from its source in the North York Moors, through Pickering to the confluence in Kerry Misperton.
Characteristics of the drainage basin
The catchment has an area of 68km2, covering moorland, coniferous forest and arable farms. The river runs down a narrow valley, which is only wide enough for the stream and the North Yorkshire Moors Railway Line.
What is the geology of the area
Gritstone- which is impermeable, and limestone
How does rainfall causes flooding there (physical)
High levels of rainfall causes an increase in the discharge of the river, therefore increasing the likelihood of a flood. The discharge of the river fluctuates a lot, with a high of 42 cumecs in 1997, and a low of 4 cumecs in 1985 (averages for the year) and an average overall between 1970 and 2010 being 14.4 cumecs. This uneven discharge is likely to be cause by varying levels of rainfall. Higher discharges often in jan, feb, nov, as these are colder months and precipitation is more likely as condensation occurring more due to a drop in temperatures.
Geology and soil type causing flooding (physical)
The catchment area consists of gritstones and limestone. Gritstones is a fairly hard rock, which suggests that water cant infiltrate as easily into the ground, suggesting a high level of surface runoff to the river, increasing the discharge and increasing the likelihood of flooding.
How does relief cause flooding there (Physical)
The town is at is of summer flash floods due to the steep nature of the catchment. Also, if its steeper, then its likely that water will reach areas faster, and a flood will develop quicker.
How does agricultural land use cause flooding (human)
In the headwaters there is moorland and in the lower catchment there is arable farming. Inappropriate cultivation of arable soils, overstocking of grasslands, excessive moorland and forestry drainage, and poor river management are al thought to have increased the risk of downstream flooding.
How has urbanisation cause flooding (human)
Urbanisation increases the discharge of the river, because impermeable surfaces, such as roads, are made which increases surface runoff as water infiltrates less/ cant infiltrate. This increases discharges of rivers and therefore makes flooding more likely.
How does moorland and forest drainage cause flooding (human)
Getting rid of vegetation (peat digging) is likely to cause an increase in the amount of water going into the river, as less is being taken in by plants, increasing the likelihood of flooding.
Human impact on water
Over farming has caused fertilisers and effluent to run off into waterways, which adds toxins into the water.
Management of flooding and impacts- slow the flow scheme
Slow water entering the catch emend gets stored in the middle of the catchment, which improves outflow as water exits the catch emend slower.
Management of flooding and impacts- targeted blocking of moorland drains
Drains blocking can help to re-wet peats and slow down runoff. 187 heather bale check dams have been constructed within moorland drains and gullies in the Pickering beck catchment to improve water retention and delay the generation of flood flows. In addition, 3.2 hectares of heather habitat have been reseeded and 800m of eroding footpaths repaired.
Management of flooding and impacts- no burn zones
Heather burning has the potential to speed up runoff by temporarily removing the vegetation cover and promoting hydrophobic soil conditions. 10m wide no burn buffer zones face been established along the main watercourse in the upper catchment of Pickering beck as a part of a 10 year Environmental Stewardship Scheme. Burning moorland removes vegetation and speeds up upland flow, so preventing this will reduce the risk of flooding, as water will be taken in by the plants.
