topic 4 : river management

why is flood risk increasing in the UK?

• increasing population so more housing being built on floodplains

• changes to land use e.g more impermeable surfaces so greater surface run-off

• changes to weather patterns due to climate change e.g storms, drought

dams and reservoirs - hard or soft?

hard engineering

river straightening and dredging - hard or soft?

hard engineering

embankments (levees) - hard or soft?

hard engineering

flood relief channels - hard or soft?

soft engineering

demountable flood banters - hard or soft?

soft engineering

flood barriers/storm surge barriers - hard or soft?

hard engineering

flood warnings and preparation - hard or soft?

soft engineering

floodplain zoning - hard or soft?

soft engineering

river restoration - hard or soft?

soft engineering

positives of dams and reservoirs

• can attract tourists

• can be used to produce electricity by passing water through a turbine within the dam

negatives of dams and reservoirs

• dams trap sediment - reservoirs can hold less water

• habitats are flooded so leads to rotting vegetation

cost of dams and reservoirs

very expensive

positives of river straightening and dredging

• more water can be held in the channel

• can be used to reduce flood risk in built-up areas

negatives of river straightening and dredging

• dredging needs to be done frequently

• speeding up the river increases the flood risk downstream

cost of river straightening and dredging

expensive

positives of embankments (levees)

• cheap with a one-off cost

• allows flood water to be contained within the river

negatives of embankments (levees)

• looks unnatural

• water speeds up and can increase flood risk downstream

cost of embankments (levees)

cheap

positives of flood relief channels

• removes excess water from the river channel to reduce flooding

negatives of flood relief channels

• expensive to build

• if water levels continue to rise, the relief channel may also flood

cost of flood relief channels

expensive

positives of demountable flood barriers

• good for places where a permanent sea wall would look ugly

• more cost efficient than permanent barriers

negatives of demountable flood barriers

• need 24 hours warning to set the barriers up so risk that not installed in time

• can only be used in that specific location

cost of demountable flood barriers

cheap

positives of flood barriers/storm surge barriers

• can protect large areas from storm surges

• the gates can be closed when a high tide is forecast

negatives of flood barriers/storm surge barriers

• construction costs high

• regular maintenance needed

cost of flood barriers/storm surge barriers

very expensive

positives of flood warnings and preparation

• people have time to protect their properties

• many posessions can be saved, resulting in fewer insurance claims

negatives of flood warnings and preparation

• some people may not be able to access the warnings

• flash floods may happen too quickly for a warning to be effective

cost of flood warnings and preparation

fairly cheap

positives of floodplain zoning

• more expensive buildings and land uses are further away from the river, so have a reduced flood risk

• less damage is caused

negatives of floodplain zoning

• not always possible to change existing land uses

• planners have to decide what type of flood to plan for

cost of floodplain zoning

cheap

positives of river restoration

• restoring meanders help to slow down the rivers

• natural rivers are more attractive and better for wildlife

negatives of river restoration

• flooding is still likely

• flood banks will still be needed

• may result in change of land use

cost of river restoration

cheap at first, but gets really expensive