Monday, July 23, 2007

How we have made the floods worse

Inevitably, there has been a lot of talk about global warming and climate change. But human action has made the current floods worse in two more tangible ways.

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:

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.

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.

The second is through the concreting over of front gardens in the cities. In September 2005 the environment committee of the Greater London Assembly published a report entitled Crazy Paving: The Environmental Importance of London Front Gardens (.pdf format).

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.

So there at least two ways in which recent changes to the urban and rural environment have made the current floods worse. The government should address them as a matter of urgency.


Stephen Tall said...

On pavements, 2 points:

1. I suspect most of the times that concreting over of front gardens takes places it's either because (i) the house is being converted into flats (which require more off-street parking) to reduce the pressure on housing, and to reflect the smaller size of families today; and (ii) local councils have introduced residents-only parking to protect communities from the negative impacts of commuter parking, then started charging for the permits - so residents make off-street parking where they can.

2. Concreting over your front garden is part of a house-owner's permitted development rights. They do not need to seek permission from the planning authority to do it. Would any government dare to over-turn this?

In both cases, the matter is, to some extent at least, in the hands of local councils, and better dealt with at that level. (Cf the moves to fortnightly rubbish collections, which work in some places and not in others.)

David said...

Your comment illustrates how climate change can only be seriously confronted by government action. Individual actions (like Donnachadh McCarthy's solar panels)can bear witness and encourage politicians but not solve the problem. Keeping the same number or more motor vehicles in cities and keeping current planning policies are not options if we are serious about climate change.

Anonymous said...

There's a letter in the Times today pointing out that it is possible to get porous asphalt.

Rob Parsons said...

The previous MP for Lewes was Tim Rathbone, who had great difficulty believing his eyes when he lost the constituency in 1997. Tim Renton was MP for Mid Sussex.

Jonathan Calder said...


Many thanks - I have edited the post in the light of your comments (and to reflect the fact that Lord Renton is happily still with us).