4.8 - Flood Risk And Management Flashcards
Why is river flood risk increasing?
Flood risk is rising due to 2 main factors : Global climate change and human processes. Climate change causes increases in water volumes, storm occurrences and severity and heavier, more extreme rainfall and precipitation. Human processes are land use changes and are things like expanding urban areas, removing vegetation and permeable rocks and soils, and more developments on flood plain areas.
Compare how soft and hard engineering schemes work
Soft engineering is when processes are implemented and work with nature instead of against it, for example, afforestation is a type of soft engineering as planting trees helps with interception of water and decreases surface run off and all in all works with nature. However, hard engineering processes work against nature, for example, flood walls are a hard engineering process which act as barriers to surging waves and stop them from flooding and breaching the natural defences.
Explain what each hard engineering scheme is, how they work and the pros and cons
Flood walls - artificial barriers built along river banks. They’re designed to increase height of the river banks allowing the river to hold more water. However, they are very expensive and can be unsightly and block the view of the river.
Embankments (Levees) - High banks that are built along or near river banks. They stop the river flowing into built up areas during a flood, protecting buildings on floodplains. They can be made from earth or natural materials making them less unsightly than flood walls. They’re quite expensive and there is still a severe risk of flooding if the water rises above them or breaks through.
Flood Barriers (Flood Gates) - Are built on river estuaries to stop flooding from storm surges or very high tides. They can be shut when there is a surge forecast to prevent flooding and they protect a large area of land. They are very expensive to build and need to be maintained regularly.
Flood Barriers (Demountable) - Provide temporary protection against flooding. The barriers are only put up when there is a flood forecast and there is a risk of not putting them up in time. They are quite expensive but don’t spoil the attractiveness of a location.
Explain what each soft engineering scheme is, how they work and the pros and cons
Flood Plain Retention - Maintaining the river’s flood plain, ie. by not building on it. It helps slow floodwaters down and maintain the flood plain’s ability to store water. No money has to be spent but development is restricted and cant be used in urban areas.
River Restoration - Making the river more natural. For example, removing man made levees to let the river flow naturally and flood plains flood naturally. There is less risk of flooding downstream because discharge is reduced. The river is left in its natural state and little maintaining is required. However, it can increase local flood risk, especially if nothing is done to prevent major flooding.
