5.5 Surplus in the hydrological cycle can lead to flooding, with significant impacts to people Flashcards
Causes of flooding physical factors - Meteorological causes of flooding -
For example large amounts of rainfall and low pressure systems This leads to intense and frequent rainfalls this leads to high soil water availability and saturation of soil therefore becoming impermeable and increase in overland flow.
What does meteorological mean?
Flooding may result from a large amount of rain or from rapid thawing of snow and in coastal regions may also be caused by a storm surge or a combination of high tide and high river level.
Flooding definition -
If the discharge is of sufficient quantity to cause a body of water to overflow its channel and submerge the surrounding land, flooding is seemed to have occurred.
When a river exceeds bank full discharge
A great flowing or overflowing of water, especially over land not usually submerged.
Intense storms leading to flash floods -
Can also depend on very intense storms. Like the UK storms of October to December 2015. During this period, parts of the UK experienced rainfall far above normal levels. For example, in December 2015, some areas in northern England received over 300 mm (11.8 inches) of rainfall, which is more than double the average rainfall for that month.
Widespread monsoon rainfall can result in widespread damaging of floods -
For example In Pakistan July 2010 was heavily due to Monsoon rainfall of changing and prevailing winds the primary cause being the 9000 mm of water received in one week.
Flooding can also occur from Jokulhaups of glacial outburst of floods -
In the Himalayas, glacial outburst of floods occur as ice dams melt and leads to catastrophic quick events, this is mainly a result of volcanic activity of the ice melting instantly and a sudden release of melt water. (Look at glacier stuff)
How can humans exacerbate food risk -
Deforestation, Urbanisation/land use change, Dams
Effects of urbanisation on flooding -
The creation of impermeable of surfaces for example urban areas like London where the land taken up by car parks of 25 square kilometres therefore this decreases lag time between rainfall reaching the river as overland flow is much greater than throughflow through percolation.
Changing land-use for example Agriculture and deforestation -
Has a knock-on effect of water down stream, changing land-use results less of infiltration in the ground and further more these impermeable surfaces replace replace trees which act as major carbon stores and regulate the water cycle completely through their biological processes and ability to store water.
Impacts of flooding England and Wales 2007 Summer -
costs -
- £6 million
- 12 dead
Rainfall showed 387 mm of rainfall which is more than double the average.
Greatest impacts were on the lower Severn and in Tewkesbury where the River Avon joins the river Severn leading to in total 55,000 houses flooded with damaged power supplies and water insecurity in the area.
Environmental impacts may be -
Eutrophication and damage to wetlands from over saturation of the aquatic habitats.
Eutrophication can be defined as -
Excessive richness if nutrients into a body of water, causes a dense growth of plant life and death of animal life for a lack of oxygen.
Environmental impacts of flooding -
Aswan dam was build to control flooding in the Nile but had a negative impact on subsistence farmers, and sardine fisherman, as they migrated away due to the less of the nutrient supply. The dam’s construction disrupted the natural flow of the Nile River, which historically deposited nutrient-rich sediment onto agricultural lands during flood seasons.
