Storm Chandra: Are blocked drains to blame for the recent flooding?

Following the impact of Storm Chandra we’ve seen a number of comments suggesting that blocked highway drains are the reason for the recent flooding, so we want to address that clearly.

Cllr. Jon Andrews, our Cabinet Member for Place Services, writes:- "We understand the frustration. When water sits outside your home or on the roads you need to travel, it’s completely natural to think the drains must be blocked. But the main issue isn’t drain clearance.

The widespread and significant flooding this week was driven by swollen rivers, rising groundwater and exceptional rainfall - not a lack of routine highway drain maintenance.

Highways drains are designed to deal with rainwater that falls directly onto the road. They do not have the capacity to cope when rivers spill over, fields release huge amounts of water, or groundwater forces its way up from below. Most of the flooding across Dorset came from those sources. When rivers and groundwater rise that quickly, the pipes beneath road drains become completely full, so even a clear drain simply has nowhere to send the water - especially when outfalls are also over capacity.

Our crews worked through the night and are out again today clearing debris and tackling the highest‑risk spots. Alongside this, we carry out routine, proactive maintenance throughout the year. We run a planned programme of gully emptying and drain clearance as part of our regular cyclic maintenance - including emptying gullies, clearing ditches, soakaways and pipe runs.

We work closely with organisations such as the Environment Agency as major flooding nearly always comes from several sources at once – especially in a rural county like ours, with a huge network of rivers, streams, ditches, and low‑lying areas.  Whilst the Environment Agency oversees the response to flooding from main rivers, reservoirs, estuaries, and the sea; Dorset Council oversees the response to flooding from surface water, groundwater, and ordinary watercourses.

Separately, we have also picked up on some claims that new housing developments are making this situation worse. It’s worth noting that national planning rules require new homes to be safe for their lifetime and not increase flood risk for existing communities. 

Looking ahead, responding to the climate and nature crisis is one of our top priorities, which includes helping communities become more resilient as storms and heavy rainfall become more common.

Please continue to avoid driving through floodwater, follow closure signs and check updates if you’re travelling. We’ll keep clearing what we can as water levels fall."