Liverpool integrated urban drainage: a partnership approach

Abstract

A preliminary flood risk assessment estimated that 20 100 households in Liverpool are at risk of surface water flooding in a once in 200 year event. This paper describes a detailed investigation to reassess the numbers and locations of properties at risk, and then to determine the possible solutions and associated costs. The investigation involved integrated working between Liverpool City Council, the Environment Agency, United Utilities and CH2M. The project included data collection; integrated hydraulic modelling of the sewer network and watercourses (including overland flow modelling) using InfoWorks 2D; analysis; high-level option development; and cost–benefit analysis of the potential solutions. Solutions considered included surface water management, culvert rehabilitation and optimisation of the sewerage and watercourse infrastructure. The technical aspects discussed in this paper include creating the integrated model, flood mapping, ‘hot spot’ identification and modelling of possible flood alleviation options. The project will enable creation of a multi-agency investment and action plan to reduce the risk of flooding in high-risk locations. The paper also reviews the advantages and disadvantages of the project for all the parties and discusses what lessons can be learnt for future integration and partnership.