River flooding and flood management

The River Rhine - MEDC

What caused the floods?

In January 1995 rivers flooded all over Europe. The floods caused millions of pounds worth of damage and caused a quarter of a million people to be evacuated. The floods were caused by excess rainfall in the Alps at the source of the Rhine. Warm wet weather melted the snow, ice and glaciers filling streams and rivers. All over Europe it was raining. At first the soil soaked up the rain. The water percolated through the soil and was transferred via ground water into watercourses. As it continued to rain, the ground became saturated and surface run-off increased. It took the river a few days to peak due to the initial percolation.

By January the 27^th, the water level in Cologne on the banks of the Rhine had risen 10.2 metres. The Army was brought in to help protect the city. They built up walls of sandbags. 11,000 were moved in 4 to 5 days.

Humans have changed the environment in several ways, which speeds up the rate at which rain runs off and into rivers. Rain in cities rushes straight into rivers. Three times more of the area is built up than in 1900. Land has been intensively cultivated. As a result it becomes compact and can't absorb as much water. Meadows allow water to be absorbed, as the ground is more porous. There are more ploughed fields than there used to be.

In January 3 times more water fell in Switzerland than normal. In Cologne, barriers were built to try and protect property. The River Maas was overflowing in France, Belgium and Holland. In Well temporary dykes were constructed to protect homes and businesses. The school had to be evacuated and moved to temporary accommodation. People were evacuated from their homes. 50,000 people were evacuated along the River Maas. Some went to specially arranged evacuation centres.

How has river management made floods worse?

The natural river was a meandering braided channel. The river was straightened and narrowed to accommodate barges and enable dykes to be built to protect the towns on the bank. As a result the river flowed quicker. The river is now 50 km shorter than it used to be. When there is a flood surge the water flows quicker and reaches the areas downstream sooner. Previously it took 5 days to reach the areas downstream, now it takes just 2 days, consequently the same amount of water is being squeezed into a smaller area resulting in higher flood levels. When the evacuation took place roads became congested, farmers had to move large numbers of cattle. The farmers and other businesses lost a lot of money. Compensation was hard to come by due to the amount of damage caused by the flood.

What can be done by local people to reduce the risk of flooding?

People in the village of Well on the River Maas can protect themselves and reduce the effects by doing a number of things: Cupboards and units can be hung on the wall rather than placed on the floor so that the water doesn't reach them. Tiles on the floor to reduce the cleaning up operation can replace carpets. Furniture can be moved upstairs once a warning has been issued.

People still live in these areas despite the risks as they enjoy the freedom, countryside, canal for fishing and open spaces for various recreational activities.

Local businesses can protect themselves. One café has installed concrete columns which have grooves cut into them. When it floods barriers are slotted in to stop the floodwater. Gaps in windows can be filled with foam, which expands when in contact with water. Old homes have been built above ground level with steps up to them.

Other strategies.

3 km of dyke now surrounds the village of Well. Most are simple earth dykes made of sand and soil pilled up. Some are lined with stones to protect them from scouring by the floodwater. Others have been strengthened by steel so they can be built higher and thinner.

More forest gives more time for excess rain to be absorbed before it enters the river; therefore management must begin upstream. As the river basin covers 9 countries this management must be co-ordinated internationally. Forested areas need protecting as people demand more land for building, industry and farming on the floodplain.

In cities such as Strasbourg, the area is covered by impermeable surfaces. The river is confined in a narrow channel. A dyke and retention basin has been built which allows water to be siphoned off for 10 - 12 hours when water levels get too high. Another option is to build in areas between the river and dyke which is allowed to flood. This enables the area to hold more water without flooding the settlement behind. Trenches can also be dug into the foreland to hold more water. The mud removed can be used to build dykes and make bricks for building.

D.Drake 2008