Working with nature on sustainable drainage solutions: Why a well-managed green infrastructure approach is so important

View of a main road with houses on the far side, and a grass swale with gabion wall on the near side

Sustainable drainage systems (SuDS) are nature-based solutions which are contributing to improved urban resilience and climate adaptation in increasingly developed and (peri)urban landscapes.

This green infrastructure approach provides social, economic and environmental benefits: it creates natural spaces that are good for mental health and wellbeing, reduces the risk of flooding, means less water treatment work is required, lower costs, lower energy consumption and, ultimately, lower carbon emissions.

Image: Grass swale with gabion wall on one side in Beaulieu Keep, Chelmsford. Credit: Maryam Imani/SuDS)

SuDS can include, amongst other solutions, grass swales, water basins and trenches, wetlands and ponds; they are an important component in the Government’s journey to net zero by 2030.

A lot of work has gone into the optimal design of SuDS to minimise flooding and water contamination, and they are becoming an established feature of our landscapes. New developments with much more green space conceal the hidden complexities of these nature-based drainage solutions, which are being formed across the country.

There is currently limited legislation and guidance for the maintenance of SuDS which can be costly and complicated. Yet, if not properly maintained, then these nature-based drainage solutions will become part of the problem instead of being part of the solution.

'Although SuDS mimic natural drainage systems, they are not just green areas,' explains Dr Maryam Imani, Associate Professor of Water Systems Engineering at ARU, who is leading a team investigating SuDS design and maintenance.

'SuDS have to be integrated into the grey (drainage system) infrastructure; they are engineered to maximise infiltration capacity so water can be quickly absorbed into the soil and the impact on the drainage and sewerage systems can be minimised.'

Remote sensing technologies are already being successfully deployed in structural health monitoring systems and Dr Imani and her team are working on a proof-of-concept study to propose a smart system to monitor the growing SuDS network. Using state-of-the-art artificial intelligence-driven models and remote sensing technologies, they are investigating systems to automate the SuDS monitoring and maintenance process.

The research will help to establish whether this technology can be used to enhance the long-term performance of SuDS installations and reduce inspection costs, which currently rely heavily on visual monitoring carried out by people, some of whom may not be very well trained.

Dr Imani and her team – which includes ARU academics Dr Reuben Brambleby, Dr Binh Le, and Dr Mahdi Maktabdar Oghaz – are building two physical SuDS models in the lab – an infiltration trench and a grass swale – both equipped with smart technology to constantly monitor the health of the drainage system. The technology includes thermal imaging, wireless sensors and digital devices to measure data including soil moisture content, temperature, water depth, infiltration and flow rates.

The team will also be monitoring vegetation growth, silt/sediment and litter build up as key maintenance factors. They aim to re-create "real-life" scenarios to see how the systems perform and what maintenance is required.

'We need to understand how the growth of grass affects the hydraulic capacity and infiltration rate of a grass swale, so we know when grass needs to be cut,' explains Dr Imani. 'We need to know if silt and sediment in underground voids of an infiltration trench is adversely affecting infiltration rates so we can identify the areas for maintenance.'

'We will look, for example, at the performance of grass swales with short, mid-length and long grass,' continues Dr Imani. 'We will use the data from our modelling to predict the critical areas for maintenance. The AI-driven model will generate heatmaps to visualise the maintenance hotspots that require urgent attention.

'Our model will provide the first steps towards digitising SuDS inspection – advancing from a manual process to a more all-encompassing, systematic, data-driven approach.'

The team will be monitoring the lab-based models for about four to five months so they can start to understand the data and make realistic predictions. It is hoped that the research can then be transferred to a ‘living lab’ embedded within the ARU Chelmsford campus where the team can factor in real-life social and climate conditions.

In the long term, Dr Imani is already in discussion with Essex County Council about setting up trial areas for smart monitoring.

'Climate adaptation is one of the critical items on the Government's priority list,' concludes Dr Imani. 'SuDS are one of the best adaptation strategies around flooding and have huge potential in carbon emission reduction/carbon sequestration.

'These nature-based solutions allow us to work with nature, not against it, but we need strategies and technologies in place to effectively monitor and maintain the systems.'

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