2 Nov 2012

Higher risk of winter floods after a wet summer

The Environment Agency, in conjunction with the Met Office, released its autumn/winter flooding outlook today.

It highlights that following the wettest summer in 100 years, there’s a higher risk of flooding for the rest of autumn and this coming winter in England and Wales.

This is a remarkable turn around of events given that earlier this year much of England was in the midst of an official drought following two consecutive winters of below average rainfall – winter being a time of year when rainfall is crucial in replenishing our water resources.

Normally during summer, it is very difficult for rain recharge water resources because evaporation rates are higher and growing plants take up a lot of water through their roots.

However this summer, due to the sheer volume of rainfall and the lack of any prolonged dry, hot spells, water has managed to percolate downwards into the aquifers, with a rapid and unprecedented turnaround of our water resources.

Whilst this turnaround has rid us of official drought status and hosepipe bans, it has put river, reservoir and groundwater levels at unseasonably high prior to the time of year when we experience our wettest weather.

In effect, the ability to cope with heavy rainfall in the coming months has been significantly reduced, and, as a result, the risk of flooding is elevated compared to a normal year.

What are the main concerns?

The Environment Agency and Met Office are warning that there is an increased likelihood of flooding from rivers in November and December, especially in south west England. Northern and western parts of England and Wales also have an increased risk after recent heavy rainfall.

Groundwater levels are also unseasonably high following this summer’s unprecedented rainfall. There is an increased risk of flooding from groundwater in the south and east of England with Devon, Dorset and Hampshire particularly at risk.

Flooding from surface water – where the amount of rainfall overwhelms the drainage network – is more likely as the ground is already saturated and unable to soak up any more water.

The risk of coastal flooding also increases at this time of year, especially during periods of high spring tides from 12-18 November and 12-18 December.

What is the weather trend for November?

November is a notoriously difficult month to forecast for too far ahead because it can experience such a range of weather.

Whilst balmy days with hints of an Indian summer can occur, early blasts of winter from the Arctic are just as likely.

Having had a look at the weather charts for the first few weeks of November, the general trend for the UK suggests a largely unsettled theme, with low pressure the dominant feature.

As a result, showers or longer spells of rain can be expected, with occasional drier spells in between.

There are also hints that it’s going to be quite cold, with brisk winds often varying between westerly and northerly direction, with snow possible – especially over the hills.

Fall in roads deaths due to wet weather?

Staying with the impacts of the wet weather, provisional government figures released yesterday show that the number of deaths on the roads this spring fell sharply, with an 18 per cent reduction compared to the same period last year.

The Department for Transport (DfT) commented that the wet weather experienced in this period is likely to have reduced levels of pedal and motorcycle traffic in particular.

They said that there is also evidence that the wet weather may have affected road-user behaviour through reducing traffic speeds.

Once again, this demonstrates the effect that the weather has on us all, even on a subconscious level.

Don’t forget, you can get the latest five day forecast on the Channel 4 Weather website and you can follow my updates on Twitter – @liamdutton

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