From closed roads to poonamis, we know North Dorset’s flooding is getting worse – Rachael Rowe asks what’s causing it (apart from more rain)
The last weekend in January was a storm to remember, as winds and torrential rain reached North Dorset. Rain described as “biblical” in nature streamed down on the Blackmore Vale, with many places rapidly flooding. For a while, roads across Somerset and Dorset were closed, with cars stranded in floodwater.
North Dorset has well-known local flood spots – most people will avoid Hammoon and Caundle Marsh in very heavy rain, for example. However, what surprised many people were new areas with significant floodwater. How often does the A303 flood, for example?
The A357 between Shillingstone and Sturminster Newton was closed while investigations took place into the flooding. The amount of water caught people out, stranded several cars. A Dorset Council spokesperson responded: ‘There are no specific known issues with our drainage here: it is likely to just be volume of rain falling in a short period of time that is overwhelming them. We operate a cyclical gully cleansing regime to clean the gullies all around the Dorset Council area and gullies are also checked during routine highways inspections. Unfortunately, some weather events mean that the gullies cannot handle the amount of rain that falls in such a short period.’
Blandford farmer (and BV columnist) George Hosford had some insights into the flooding. His ‘early flood warning system‘ – his 92-year-old father John – generally looks out of the window and tells him when cattle should be moved away from the Stour. George also measures rainfall on the farm and used to see an average of 1,050 ml a year: ‘The last three years we’re seeing an average rainfall of 1,400ml which is a significant increase. It’s down to climate change. Since September last year the Stour has been out five times. It used to be just twice a year. The problem is always a large amount of rain in a short space of time.’
Run-off from fields is another issue. ‘There’s a lot of maize being grown to feed cows and anaerobic digesters. While it’s good for producing carbohydrate, it has a very long growing season. As a result of using the heavy machinery, the soil can get damaged, causing an increased run off of water. With maize crops, some farmers plough up and down, whereas if they ploughed across a field it would slow down the run off. Some fields are also left with maize stubble in winter: with no other vegetation, there’s nothing to slow the run-off.’
The brown stuff
One very unpleasant aspect of the storm was the sewage outfall. SewageMap.co.uk is an online mapping tool that shows, in real-time, which river sections are downstream of sewage discharges from storm overflows. After Storm Herminia, parts of the Blackmore Vale map appeared to have been hit with a giant poonami. It’s a very interesting website – just don’t browse while you are eating.
It wasn’t just the fields drowning in sewage. Some unlucky residents with surprise bathroom floods – thanks to those overworked drains – discovered that their neighbours have been flushing wet wipes (seriously, please don’t do that).
Busy emergency services
Naturally, the emergency services were busy dealing with the adverse weather. The Environment Agency had an incredibly demanding weekend, working to protect lives and properties in Somerset.
The impact was also widely felt in Dorset, where the southern communities faced a heightened risk of coastal flooding. A spokesperson said: ‘We have warned nearly 17,000 people and 9,000 properties in the past three days (Sunday 27th to Wednesday 29th) and supported local authorities and fire services with evacuating people at Somerton and Ilford.’
A spokesperson from Dorset Council said: ‘We responded to 14 call-outs: 12 for flooding and two for fallen trees.
‘We made three road closures, all due to the amount of heavy rainfall in a short period. These were the A350 Beacon Hill, Wheatsheaf Hill – the county boundary between Sherborne and Corton Denham – and at Knoll Lane, Corfe Mullen. We also monitored the Portland Road beach road for two consecutive nights, in case the sea came over the beach on to the road. Spring high tides and the wind direction increased the likelihood of the waves overtopping the road, but this did not happen.’
Dorset Fire and Rescue were also busy, on shouts and advising people not to drive through floodwater. ‘Over those two days, we received 20 weather-related calls, three of which were in North Dorset. We attended four of those 20 calls, which were all to assist drivers who had tried to drive through flood water.
‘The biggest challenge we always face is getting the public to follow our advice of not trying to drive through flood water. Our advice for driving in adverse conditions can be found on our website – dwfire.org.uk.
Reducing flood risk
With increased adverse weather and higher rainfall, what can be done to reduce the risk of flooding? George Hosford had a couple of suggestions:
‘There should be no building at all on flood plains … no car parks, no buildings and no roads. The Upper Stour is not a naturally flowing river any more. It has been deformed by dredging and building mills and weirs. If farmers in the upper catchment, where the tributaries flow, were given incentives to allow fields to flood for a period, less water would come downstream all the way into Christchurch.’
The Environment Agency noted that with climate change, flooding will be more frequent. It encourages people to sign up for flood warnings. However, with that increased frequency comes the need for more creative solutions to protect the North Dorset infrastructure.
