River Management Methos Flashcards
Positives & Negatives of Dams
+ Reduce flood risk by storing water especially when there has been heavy rain. Can be used to generate HEP and the reservoir can be used for recreation.
-Dams are hugely expensive to build. Completely change the natural landscape of the river basin in the area round about. The reservoir can cause the loss of farmland and displacement of people. Sediment is trapped behind the dam which prevents the deposition of alluvium downstream. If a dam fails the consequences will be calamitous
Positives & Negatives of Embankments
+ Increase capacity to hold more water which in turn reduces the risk of flooding. Allows building on the floodplain and the protection of agricultural land
-Flood walls are effective when built high enough. However they are expensive do not look natural, require maintenance and restrict access to the river side
Positives & Negatives of straightening the river
+As well as reducing the flood risk, straightening makes rivers easier to navigate
-Not natural looking. wildlife habitats are disrupted by removal of meanders. rivers can return to their original natural course. by straightening a river upstream, so increasing the speed at which the water moves through the channel. Increase risk of flooding downstream
Positives & Negatives of Deepening the river
+Allows the river to contain more water and so the river is less likely to flood.
-River will continue to deposit silt into the channel and so dredging needs to be done frequently. Heavy machinery required, and so this can be expensive over long distances. Deepening the channel allows water to move through it more quickly and rapidly to areas downstream which may flood as a result
Positives & Negatives of Washlands
=Low maintenance, low environmental impact option. For plants/animals which thrive in the types of wetland which are often under water, wash lands provide a new habitat
-Washlands require large area of land which cannot be used during the flood event
Positives & Negatives of Land use zoning
+Allows the river to flood but reduces the disruption and damage caused, including reducing insurance claims. It requires no structure to be built and so is cheap and easy to carry out. creates more green space which encourages infiltration and reduces OLFW
-Zoning cannot be applied to areas which are already urbanised since people and businesses would have move. Restricts building in some areas and can be seen as reducing the land available for development so pushing up land values
Positives & Negatives of Afforestation
+Afforestation will not prevent flooding but can reduce it’s impact. Relatively cheap and creates wildlife habitats. produces timber and the soil is help in place by tree roots reducing soil erosion.
-Afforestation takes time, requires a lot of available land to be affective and must be carefully managed to include a variety of native tree species
Difference between hard methods and soft methods
Hard methods attempt to contain water and prevent flooding. to do this they require major alterations to the river including the building of large artificial structures. Soft methods do not attempt to prevent flooding but rather reduce the impact of flooding when it happens; to do this fewer alterations to the river are required, indeed they are generally sympathetic to the natural environment
What does sustainability mean
Sustainability means meeting the needs of the present without compromising the ability of future generations to meet their needs.
What does Hard engineering mean
Hard engineering is a method of river flood management which involves major constructions. Hard engineering involves major alterations to the river and is often less sustainable
What does soft engineering mean
Soft engineering is a method of river flood managements which works or attempts to work with natural river processes. It does not tend to involve major construction work. Since soft engineering is seen as more sympathetic to the environment it is generally considered more sustainable.
