City of York Council has been working with partners at Yorkshire Water, the Environment Agency and local Internal Drainage Boards to try to minimise the impact of any future localised flooding, following the floods of June 2007.

Members of the council's City Strategy Advisory Panel will learn about the findings of a review of the events in the summer at a meeting on Monday 10 December.

The review states that the overwhelming cause of the flooding in June 2007 was the high intensity of rain falling on ground that was already saturated and caused significant run-off - far greater than the capacity of sewers and watercourses, which are designed to cope with rainfall of a level expected once in every 30 years.

The monthly rainfall for June 2007 was over 170mm, three times the long term average.  The rainfall events ranged from 1 in 7 to 1 in 100 year occurrence.

Records show that 138 locations reported flood related problems in York, of which seven were believed to be homes suffering from internal flooding.  Problems ranged from: flooding on the highway, blocked gullies/drains, sandbags being required, flooding almost entering properties and flooding entering properties.  

During and following the heavy rain there were many discrete areas of the city, which suffered from flooding of property, gardens and highways.  These were clustered principally in five areas of the city, Haxby/Wigginton, Rufforth, Strensall, Clifton/Rawcliffe and Acomb/Holgate, with others randomly distributed, and were locations different to those, which normally experience river flooding.

The council deployed 12 personnel, three tankers, two pumps and approximately 1,000 sandbags to assist in the relief operation.

The review suggests that in many cases the volume of rain was just too great for the sewers or drains to cope with. Some watercourses were running full and could not accept the water that was being discharged from the surface waters sewers. Also highway gullies could not cope with the water, as they were overwhelmed with the volume of water or required cleaning. 

Members will be asked to agree to proposals for the council to continue to work with Yorkshire Water and the Internal Drainage Boards to see if there were any defects, which contributed to the flooding. Yorkshire Water is already working with local authorities across the region on a programme of de-silting sewers.

The council has already requested a review of the maintenance of the roadside galleys, which drain the highways, to ensure that they are able to cope with large rainfalls.

There are approximately 40,000 road gullies under the council’s control and these are cleaned on a planned basis. There are also about 1,000 gullies situated in the back lanes of terraced properties, and an estimated further 1,000 gullies in footways. 

In addition, the council creates and maintains around 7,500 roadside grass verge grips on rural roads.  These are the earth slots cut into grass verges to drain water from the carriageway.  These are normally cut in the late summer/early autumn in readiness for the coming winter and to assist with this form of drainage, a number of roadside ditches are also cleaned periodically.

Councillors will be asked to consider allocating additional funding to facilitate the maintenance programme as part of the authority’s budget proposals.