CORE UNIT: PATTERNS AND PROCESSES IN THE PHYSICAL ENVIRONMENT
Continued urban sprawl and reduction in farmland has meant run-off from rain reaches streams and rivers more quickly than in the past. Instead of rainwater seeping through the ground and taking many days to reach the river, it now reaches it quickly in a matter of hours through pipes and drains. It used to take up to five days for a flood surge to pass downstream but today, due to man’s control of the river’s natural processes, it takes three days. This has led to increased flooding during heavy rains. The flood water put great pressure on the polders/reclaimed land and levees along the river. Floods in 1995 and 2002 saw the Rhine return to much of its natural course. Holland spent €1.3 billion on flood control measures in the 1980s. Its polderlands are protected by levees of 10 m high.
During floods in Strasbourg, the
authorities pump water into retention basins outside the levees. These basins reduce the floodwater height by 60 cm for 10–12 hours. When the flood has receded the water is pumped back into the river. These retention basins are then left as nature reserves or grazing land.
North Sea NETHERLANDS Amsterdam Rhine Rotterdam Nijmegen