Geared to protecting 548 residential and 96 commercial properties in Ripon, the challenging Ripon Rivers Flood alleviation scheme now nearing completion, is geared to protecting the city which has a long history of flooding because it is situated where the rivers Skell, Laver and Ure meet.
Improvements are also being made to clear the flood arches of some of the existing bridges in the city, an existing weir is being replaced and a new river gauging system is being constructed further upstream. By removing and replacing the weir, the water level in the Skell at this location has been lowered by between 0.5 and 1m.
The River Ure has caused flooding to properties in Ripon and coinciding peak flows in the River Skell and River Laver (a tributary of the Skell) have also caused a large head of water to go through the town.
In order to stop the two peaks flows from happening at the same time, a new earth retaining dam known as Birkby Nab measuring approximately 400 metres long, and 90 metres wide has been constructed to hold back water from the River Laver. This has lowered the level of the River Skell by between 40 mm and 1 metre.
Other works completed downstream on the River Skell at Borridge Lane comprised individual bespoke schemes in approximately 15 rear gardens of private properties, which involved raising ground levels by approximately 700mm both through the installation of new flood walls and the utilisation of existing flood defences.
Still further downstream where the River Skell discharges into the River Ure, the height of the concrete Alma Wier which spans the River Skell and previously caused water to back up behind it has been lowered, resulting in a lowering of the water level by approximately 1 metre.
Further downstream on the River Skell at Fisher Green, a l metre high 250 m long earth embankment has been created on the left bank, whilst on the right bank 250 m of gabions stabilised with a sheet pile toe and around 4000 tonnes of clay behind have been installed, together with elements of drainage to raise the defences in that area.
Works at the town’s historic North Bridge on the north side of Ripon provides protection from flooding by the River Ure through the installation of over 230 m of new embankment up to 4 m high, together with a sheet piled retaining wall and minor roadworks to raise the road level slightly.