The Eden Basin Flashcards
The river Eden flows through Cumbria
The Eden drainage basin is in north-west England, between the mountains of the Lake District and the Pennines.
The river basin is largely rural, although the River Eden does flow through the city of Carlisle.
The upland areas that drain into the River Eden experience extreme weather that can cause flooding downstream - Carlisle is particularly vulnerable as it’s at the confluence of the Eden, Petteril and Caldew rivers, and is fairly low-lying.
Characteristics of the Eden basin affects the water cycle
1)Rainfall is higher than the national average in the Eden Basin, because of the relief of the area the mountainous terrain encourages orographic rainfall (see p.5). High rainfall means that lots of water enters the river channels.
2) The Eden Basin is long and relatively narrow, which increases lag time.
3) The slopes within the basin are steep. This reduces lag time and increases peak discharge.
4) The basin is made up of a number of different types of rock:
The highest ground, to the west of the basin, is made of igneous rocks, which are impermeable (water won’t soak into them). Infiltration is very slow and surface runoff is high in these areas, reducing lag time.
Much of the basin, however, is made up of limestone and sandstone, which are permeable. When precipitation falls in these areas, infiltration is quick and there is little surface run off, increasing lag time. The amount of water in ground stores increases.
Farming has caused changes in the water cycle, increasing the risk of flooding.
1)More intense farming has caused soils to become compacted, e.g. by heavy machinery or trampling by livestock. Between 2000 and 2009, there was a 30% increase in the number of cattle in the Eden Valley, meaning that much more land is likely to have been trampled.
2) Compaction of soils reduces infiltration, so surface runoff is higher. This means water levels in rivers rise quickly during heavy rainfall, increasing the risk of flooding.
3) Grazing in upland areas, e.g. hill farming of sheep, has also reduced the amount of vegetation that can intercept rainfall, resulting in more water reaching rivers.
Construction has caused changes in the water cycle, increasing the risk of flooding.
Although the majority of the Eden Basin is rural, built-up areas have increased. Many new housing estates have been built in and around Carlisle in recent years, e.g. the Eden Gate development to the north of the city, and there are plans to develop a huge ‘garden village’ to the south of the city, including up to 10000 new homes.
Surfaces in built-up areas tend to be impermeable, which reduces the size of infiltration flows and greatly increases the size and speed of surface runoff flows
Some new developments, particularly near Carlisle, have been built on floodplains. This has created a flood risk to property and has required the construction of flood defences to protect homes. Building on floodplains can cause flooding downstream as water that would naturally infiltrate on the floodplains flows downstream instead.
Deforestation has caused changes in the water cycle, increasing the risk of flooding.
1)Deforestation has taken place in the basin for thousands of years, e.g. to provide timber, and land for farming. Much of the original forest cover in the Eden Basin has now been removed, giving way to large areas of open grassland and heathland.
2) Trees increase infiltration and decrease runoff, so fewer trees means more runoff, flashier flood hydrographs and a greater risk of flooding.
Climate change is predicted to change rainfall patterns in the UK. For example, parts of the western UK could get up to 35% more winter rainfall by 2080. Increased winter rainfall in the Eden Basin would increase runoff and flood risk.
Storm Desmon caused severe flooding in the eden basin
1)In December 2015, Storm Desmond caused devastating flooding in Cumbria. Some of the worst flooding occurred in the Eden Basin.
2) In some areas of Cumbria, there was record rainfall. In Shap, a village in the Eden Basin, 262.6 mm of rain fell in 48 hours between the 4th and 6th December. That’s nearly 50 mm more than the average rainfall for the whole of December.
3) Appleby-in-Westmorland and Carlisle were particularly badly affected. More than 2000 properties were flooded in Carlisle alone, leaving many people homeless.
4) The hydrograph shows the River Eden’s response to Storm Desmond. The gauging station that recorded this information is located at Linstock, just upstream of Carlisle.
