River Wey

• Location


  The River Wey is in close proximity to greater London. The lower reaches include the major towns of Guildford, Weybridge and Woking. It has two sources; the northern Wey which arises from a spring in a chalk near Allton and the southern Wey originating near Liphook.
• Physical geography


  Gravels rise up and blend with gently sloping valley sides further out from the river terrace. There are also larger flatter plains towards the Thames.

  The course of the rivers and navigation drop 30m over their combined length of 87 miles (140 km)
• Geology


  There is an alluvium covered with clayey grey soils and further out from the river terrace there is gravel
• Land Use


  The nature of the landscape along the valley is predominantly rural with Alton, Farnham, Godalming, Guildford, Byfleet and Weybridge being the main urban centres.

  There is a rich wildlife habitat and stimulated ambitious human development primarily because of the dependability and strength of the water flow.
• Level above which flooding is possible:

  2.60m
• Maximum levels (with dates)

  3.88m, reached on Tuesday 7th November 2000 at 9:30am
• Increases flood risk


  There are lots of built up areas which means a lot of impermeable surfaces which increase flood risk as they stop water being absorbed into the ground so it travels as overland flow which is faster so it can reach the river faster. In addition there are buildings on the floodplains which increases flood risk as these areas are first to flood when a river overflows.

  The town area is rather steep which means the lag time will be decreased - overland flow will reach the water faster - increasing the risk of flooding.
• impacts of the floods in the winter of 2013-2014


  Houses were flooded and pets died, belonging were lost, cars submerged, floodplains underwater

  50,000 homes across the UK are without electricity, the Energy Networks Association has said

  Some 150 properties have been flooded in England, mainly in Surrey and Kent, with numbers expected to rise - the EA has said.

  In Surrey residents were evacuated from their homes in Dorking, Leatherhead and Guildford

  Some 40 properties were evacuated in Godalming due to concerns about the River Wey
• Flood management scheme for Guildford


  Flood defences to protect Mary Road, William Road and Leas Road, around the Millbrook area to protect highway infrastructure and around the Walnut Tree Close area

  Regeneration around Bedford Wharf to integrate flood risk management measures into the development proposals

  There may also be demountable flood defences

  Flood defences that protect people, homes and businesses act as barriers to flood water. Therefore, we need to create compensatory flood storage areas nearby for the diverted flood water to go without increasing flood risk elsewhere.

  Scheme costs are not available yet as they are reviewing the options
• other strategies have been implemented in the Wey catchment to reduce the risk of flooding


  Temporary barriers in Guildford, 2014:

  Pumps and barriers that are stored elsewhere are delivered to a location to reduce the impact of flooding to homes and businesses, minimise risk to life and help reduce the clean-up required after a flood
• Water abstraction licences and permits in the Wey catchment?


  There are over 220 abstraction licences in the Wey catchment.

  Over 340 Ml/day (Ml/d = Million Litres/day) can be abstracted.

  The majority of the water is used for public water supply.
• How much water is Thames Water allowed to abstract from the Wey at Shalford per day?

  30Ml/day
• Thames Water Supplies: Which water sources are used?


  The main source is at Shalford from the river Wey or river Tillingbourne. The remainder is served by abstraction from groundwater either from the Chalk or Greensand aquifers.
• Is the Thames Water abstraction from the Wey (at Guildford/Shalford) sustainable? (refer to drought risks and groundwater; explain, using data!)


  Historically the source has been robust through drought periods such that could be maintained during the droughts. The robustness arises from the fact that combined flows of the Wey and Tillingbourne have been in excess of the abstraction requirement since the 1950's. The abstraction licence is for 30Ml/day while the minimum flow of both rivers is 68.4Ml/day so the drought risk is low as even when there is little rainfall water can still be obtained through abstraction as the water level is normally over double the threshold so even when there is less rainfall flowing into the river there should still be more than the abstraction licence. The groundwater sources are also robust under drought conditions. Although if a serious drought of greater severity than has been experienced previously occurs then increased supply to the WRZ would be provided by the drought permit option at Shalford.
• What future challenges might there be for sustainable water supply in the Wey catchment?


  If the demand for water is greater than the supply of water this could cause a problem.

  Saltwater intrusion could be a challenge as if the water becomes polluted by salt water then it would no longer be able to be used as drinking water, similarly if the water becomes polluted by litter or sewage then it would not be able to be abstracted for public use.