Hazardous weather - depressions
Two different pressure systems bring different types of weather to the UK. They are In meteorological terms, a depression is an area of low air pressure. and anticyclones. At times, the weather associated with these two weather systems can be extremely hazardous.
Depressions
A depression is an area that has low atmospheric pressure. Air rising causes the formation of clouds, which brings rainfall. Depressions often move eastwards across the UK, bringing changeable weather as they travel. The diagram below shows the changing weather that warm and cold fronts bring as they move towards the east.
Case study – the Cumbrian floods 2015
In December 2015, Storm Desmond set a new record, with 341.4 millimetres of rain falling over a 24-hour period. This led to the flooding of Cumbria and, in particular, the town of Cockermouth, despite the construction of a self-closing flood barrier in 2013.
Physical causes
The warm air from the mid-Atlantic caused Rain that occurs on high land and mountainous areas. over the Cumbrian Mountains. The warmer the air, the more moisture it holds.
- Warm air from the mid-Atlantic moved towards land due to the prevailing wind.
- The warm air was forced upwards by the Cumbrian Mountains.
- As the air cooled, it condensed to form heavy rain. The weather front stopped over Cumbria.
- The falling rain poured into the River Derwent and River Cocker.
- Cockermouth is located at the rivers' The meeting point where one river joins onto another river. and as a result, led to significant flooding.
Impacts
When analysing impacts caused by natural disasters, it’s important to divide them into three areas.
- Social - effects on people and communities.
- Economic - impacts on jobs, transport infrastructure, businesses and local and national economies.
- Environmental - impacts on wildlife, habitats, vegetation and water.
Social
- Over 43,000 homes across Cumbria and Lancashire suffered power cuts.
- Approximately 5,200 homes were affected by flooding.
- One person died in Cumbria.
- About 40 schools closed in Cumbria.
Economic
- Rail and road services were disrupted.
- Many businesses suffered through damage to property and stock.
- The estimated cost was £500 million across Cumbria. The government provided £50 million for flood victims and businesses.
- It was predicted that insurance companies would pay out up to £325 million to residents and businesses.
Environmental
- Rivers were significantly altered with increased rates of erosion.
- Heavy rain washed nutrients from soil.
- Vegetation was flooded causing habitat loss.
