28 Nov 2022

Modelling techniques to understand spills from overflows

Whole-life-cycle approach to WINEP delivery – Detailed hydraulic modelling techniques to understand spills from overflows

The current Water Industry National Environment Programme (WINEP) is a set of projects that the Environment Agency requires all water companies operating in England to complete during 2020–2025 as part of their environmental obligations. Modelling is a key element required to test solutions, provide evidence, support consultation and inform decision-making during WINEP project development.

At Binnies, we use a whole-life-cycle approach to support WINEP delivery (see Figure 1).

Infographic illustrating the modelling process
Figure 1 Whole-life-cycle approach to modelling techniques


Recently, the public and political awareness, understanding and perception of overflows have fundamentally changed as the occurrence of polluting spills to watercourses and waterbodies causing poor water quality is increasingly viewed as unacceptable.

The Environment Act 2021 and Defra’s Storm Overflows Discharge Reduction Plan (August 2022) place significant obligations on water companies to reduce or eliminate spills from their sewer systems over the next few asset management plan (AMP) periods.

The installation of Event Duration Monitors at overflows means that the detailed information they provide is becoming available to the water companies, the regulators and the public to view and analyse. With large parts of current sewer systems dating from the Victorian era, the use of modelling to truly understand why these spills occur and their root cause will be essential to sustainably address these issues.

Model build

The modelling of sewer systems has been undertaken for many years, but the level of detail that can be included has increased as technology has improved. It is now possible to show all the pipes and nodes of large catchments in one model rather than having to use simplified models that do not include the small local sewers in the upstream parts of the catchments, which is often where overflows are found. The latest software has the capacity and capability to model both the sewer system and the receiving watercourse in one place, meaning that the impact of spills on the watercourse can be assessed at the same time. Before this, modelling required multiple software packages with results transferred between them. The use of these latest models makes it possible to test multiple scenarios to develop the preferred solution and address the root cause. This enables all mitigation options to be tested and drives innovative thinking on how to solve the issues through the use of both green and grey infrastructure. However, it is important to use an up-to-date model and to have a good level of verification. Therefore, up-to-date surveys will be required to improve the accuracy of the models, including both asset and flow surveys.

Pollution from overflows or other sources has a large impact on the water companies’ Performance Commitments and Outcome Delivery Incentives (ODI), so they are looking at utilising their models to undertake ‘live’ (near real-time) modelling, enabling operational teams to be deployed to areas where pollution is likely to occur and to undertake mitigation measures to reduce any impact.

Modelling analysis

As water companies look to move towards the ideal of zero pollution from their sewer systems, models will play an important role in understanding the effect of closing overflows and where improvements are required. Modelling will be a fundamental tool in understanding why spills from overflows occur and how they can be alleviated either by the use of traditional engineering solutions or, increasingly, with sustainable nature-based solutions such as wetlands to improve the quality of receiving watercourses.

As part of our work with Anglian Water, we are helping the company to understand the cause of the pollution and using its live modelling system to predict the occurrence of pollution and flooding across the catchment. We are also developing a methodology for modelling sediment within the catchment to understand where blockages may occur and potentially influence the location of pollution and flooding.

Solution development

For Thames Water, as part of its Urban Pollution Management (UPM) studies, Binnies used the full capability of the latest modelling software to undertake studies across five different waterbodies. Dynamic modelling of quality parameters was used to understand where water quality was poor and the root cause(s). Solutions were developed that provided additional capacity either at treatment works or close to the overflows to reduce the predicted spills. Alternative options were tested to look at the impact of removing the storm flows from the network, which identified opportunities for the development of greener solutions.

Binnies’ joint venture with Salix (another RSK group company), called Solutions By Nature, enables the undertaking of modelling together with the implementation of greener solutions. Feedback from implemented nature-based solutions can be used to continually improve understanding and modelling of these sustainable solutions.

Within Binnies, the modelling team has a wealth of experience and is capable of undertaking studies of different scales to provide the pragmatic and practical interventions required. For more detailed hydraulic analysis, the team can call upon the dedicated hydraulics team to ensure that any modelling that is carried out provides the information and solutions required.

Ed Gower is a Chartered Member of the Chartered Institution of Water and Environmental Management (CIWEM) and the Technical Director of the network modelling team for Binnies’ water utilities business, with over 20 years’ experience working with water utilities clients in the UK and overseas. His technical background covers clean water, river and wastewater modelling. Ed was technical lead on modelling for the delivery of Thames Water’s UPM programme and now provides the overall team management for Binnies’ modelling teams.

About Binnies

At Binnies, we create new possibilities for humanity through our innovative approach to delivery. Backed by a culture that has stayed true since the company’s founding over 100 years ago, Binnies develops intelligent water and environmental solutions using a whole-life-cycle approach to deliver functional infrastructure and lasting environmental and social legacies. We strive to elevate the quality of life for our local communities today and for generations to come.

Binnies is an RSK group company and was formerly part of Black & Veatch.

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About the RSK group (RSK)

RSK is a leading integrated environmental, engineering and technical services group made up of over 175 businesses. The group is headquartered in the United Kingdom and has an established presence in more than 40 countries around the world.

For over 30 years, RSK has been helping organisations realise their business goals efficiently, cost-effectively and with the minimum environmental and social impact. We deliver practical solutions to some of the greatest challenges of our time. As a client-focused business, our services are constantly evolving to directly respond to or pre-empt global conditions and legislative drivers.

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Media contacts 

Binnies UK  

Sascha Noar Tel: +44 (0)1737 856219 | Mobile: +44 (0)7825 356554 | Email: noars@binnies.com