The first is through changing agricultural practices. Here is an extract from a speech that Lord Renton of Mount Harry - who, as Tim Renton, was a Tory minister and chief whip - made in the House of Lords, on 18 December 2001:
Because of the season of the year, this may not have been a factor in the current floods, but it has certainly been a factor in other recent floods.
One cause of the problem in the South Downs is without doubt the effect of intensive agriculture, especially as a result of the sowing of winter cereals. They are often sown on steep slopes which are unsuitable for such crops. The ploughing and winter sowing lead to soil erosion and the rainwater then carries silt and debris down the hills. Small gullies turn into big ones and in October and November in particular, the rainy season, the water floods off the hills on to the flood plains and into the towns.
It is essential to have new environmentally sensitive agreements which leave the land fallow during winter and encourage farmers to leave the autumn stubble. That will revert to grass or remain as stubble so that the land continues to act as a sponge, a moisture absorber, rather than what has been described as "sponges turned into draining boards" allowing the water to run off the hard compacted land on the hills that has been sown and down on to the flood plains.
The report says:
Perhaps the most worrying impact of hard surfacing on this scale is the increased burden that is placed on London’s underground drainage system by the run-off of rain from hard surfaces.
There has been much publicity about the dilapidated state of London’s underground drainage system, which was constructed by the Victorians in the 1850s and has suffered a chronic lack of investment ever since. These sewers are designed to carry a combination of sewage and rainfall. The more ground is covered by impermeable hard surfaces such as concrete or paving slabs, the less rainfall will soak into the ground and the more will run into underground drains.
At times of heavy rainfall, the drainage pipes overflow and the contents are discharged into London’s rivers. This not only results in raw sewage being discharged into the river, with associated impacts on life in the river, but at times of very heavy rainfall it can result in localised flooding when rivers burst their banks.
The experience of the flash floods of August 2004 in west London provides a dramatic picture of what this might mean – hugely expensive and significant damage to our streets and our homes, loss of clean water supply, and the overflow of raw sewage into the Thames with all its consequences for the environment and public health.