Two River Floods

Exceptionally heavy rain on 20 July 2007 rapidly brought so much water into the canal from feeder streams that some flowed over the banks in places (see below). The excessive rainfall also caused widespread flooding in the Severn Valley which later led to concern that the river might swamp the canal. This page compares the course of this event with the former record flood in March 1947.

Anxious Watch as River Rose
When the River Severn at Gloucester rises to abnormal levels, it is standard practice to close the stop gates at the lock to prevent the river flooding into the canal. In both 1947 and 2007, the river continued to rise to such a level that there was concern that it might come over the top of the stopgates. As a precaution, therefore, the canal level was lowered to help accommodate any river water that spilled over. In the event, the river did not rise that high - on both occasions it peaked at 7.72m (25ft 4in) above the lock cill.


In this 1947 photo, the river level is still rising and the canal level (on the left) has not yet been lowered to help accommodate any spillage over the gates.	In this 2007 photo, the river level is very close to its peak and the canal level (on the left) has been lowered to help accommodate any spillage.

In this 1947 photo, the river level is close to its peak, and the road along the Quay in the background is completely flooded. The tugs were on standby in case any vessel needed assistance on the river.	In this 2007 photo, the river is still rising and the road along the Quay is closed to traffic as a precaution. In the event, the improved flood defences held and the road did not flood.

Helping to Save a Substation
One complication in 2007 that did not arise in 1947 was that the canal was required to receive water pumped from an electricity substation that was flooded. The Castlemeads substation across the river from the docks was put out of action for a time, blacking out parts of Gloucester, including the docks. The Fire & Rescue Service set up huge pumps and laid eight 1000 yard long hoses from the substation to Llanthony Bridge so the water could be discharged into the canal rather than be put back into the swollen river.

Earlier Problems for the Canal
In both 1947 and 2007, concern about the river flooding into the canal was preceded by problems due to excessive water entering the canal from feeder streams. On both occasions, the flows were so great that even with all available sluices open, some water did flow over the canal banks, normal traffic was disrupted for a time and the River Frome burst its banks near Saul Junction. In 2007, the rise in canal level lifted the pontoons in the Victoria Dock marina so much that the electricity supply to the moorings was cut off. The outfall from the Sudbrook culvert under Bakers Quay caused a potentially dangerous cross flow in the canal for a time, a bank slip on the off side below Sellars Bridge brought a small tree into the canal, a nearby slip on the towpath side made the towpath hazardous and pollution booms were needed near Parkend Bridge and Sims Bridge.
The extreme rainfall in July 2007 followed a similar but less extreme incident a month earlier which caused the cancellation of the annual Saul Canal Festival (Photos)

Comparison of Floods
In 1947, the peak river level was reached eight days after the canal level peaked, as much of the river water came from melting snow far away in the Welsh mountains. In 2007, the corresponding interval was only three days, as in this case the flood was due to intense rainfall in the more local catchment area when the river level was already unusually high following a previous period of heavy rain. Other reports agree that 2007 river levels above Gloucester were higher than in 1947, and as the peak level at Gloucester lock was the same as in 1947, it seems that recent flood relief measures at Gloucester did give some real benefit.

Sources: Information on 1947 flood from TNA RAIL 864/44. 1947 photos from A Thomas.