A32 Farringdon-Chawton flood alleviation scheme

Works to reduce flooding in the Farringdon area

Flooding overview

In the winter of 2013 to 2014, the A32 highway, Lower Farringdon, parts of Chawton and the surrounding area were badly affected by flooding from a combination of rising groundwater and surface water. There is a long history of flooding in this area and the primary cause of this is the height of groundwater which is recharged by rainfall. The level varies throughout the year and generally peaks between February and April.

Hampshire County Council has been working together with a number of different organisations including the parish councils, to understand the cause of the flooding. A number of actions were developed and undertaken in the short term to help alleviate flooding. These actions were funded by the County Council and The Environment Agency who contributed £292,000 and £120,000 respectively. These Phase 1 works informed the development of longer term mitigation strategy solutions that will provide a greater level of protection from flooding.

The works are to ensure the existing drainage system, which consists of ordinary watercourses, less well-defined overland flow paths, the main river and highway drainage can function to its maximum capacity. They include:

  • removing vegetation to ensure flow paths for water are clear
  • undertaking maintenance, clearance and surveying of existing ditches, culverts and pipes
  • replacing, upsizing and installing some new pipes or culverts

The improvements will reduce costs, reduce distress and disruption associated with future flooding, minimise the impact on the local economy and help to ensure that the highway network can remain open.

The organisations involved in the A32 Farringdon-Chawton multi-agency group are:

  • Hampshire County Council (as Lead Local Flood Authority and Highway Authority)
  • East Hampshire District Council
  • Environment Agency
  • Thames Water Utilities Limited
  • Farringdon Parish Council
  • Chawton Parish Council
Project appraisal and funding

Councillor Humby, Executive Member of Environment and Transport, approved a project appraisal of the scheme on 19 September 2017. The report provides an overview of the scheme and the estimated scheme costs of almost £0.3 million.

Additional funding or contributions were sought from:

  • central government
  • the Thames Regional and Coastal Committee
  • the multi-agency partners

In early 2020, a bid for further funding was submitted to the Environment Agency and in summer 2020 additional funding of £317k was awarded.

Programme of works

The programme of works may need to change due to weather conditions or other unforeseen issues.

Milestone Timescale
Phase 1a: CCTV and land survey, trial hole investigations and ditching works Autumn/Winter 2017/18
Phase 1b: Culvert installation, further CCTV survey and some trial hole investigations Summer/Autumn 2019
Phase 1c: Emergency works carried out under Section 100 of the Highways Act during the flood event February-April 2020
Phase 2a: CCTV and land survey, trial hole investigations Autumn/Winter 2020/21
Phase 2b: Culvert installation and ditching works Spring/Summer 2021
Phase 2c: Monitoring and evaluation Winter 21/22

Plan showing the area of works. The plan may take several seconds to load. It may change following further discussions with the highway contractor.

Maintenance of ordinary watercourses

Watercourses are classified as either a ‘ordinary watercourse’ or ‘main river’. Ordinary watercourses are watercourses that are not part of a main river and include streams, ditches, drains, cuts, culverts, dykes, sluices, sewers (other than public sewers) and passages, through which water flows.

Hampshire County Council intends to work with riparian owners (those living adjacent to an ordinary watercourse) who are responsible for maintaining ordinary watercourses to ensure that the effectiveness of the existing ditches, particularly those adjacent to the A32, is improved and ensure that  future maintenance is undertaken at appropriate intervals.

See 'Reducing flood risk' guidance for further information.

Contact

Write to us at:

Flood and Water Management team
Economy, Transport and Environment Department
Elizabeth II Court West
The Castle
Winchester
SO23 8UD