Dr Josh Wolstenholme, Loughborough University                            FRE0020

Written evidence submitted by Dr Josh Wolstenholme, Loughborough University

Environmental Audit Committee inquiry on Flood resilience in England

January 2025

I am Dr Josh Wolstenholme, a Research Associate in Geoscience at Loughborough University in the Department of Geography & Environment and specialising in flood risk management. My research uses a mixture of field observations and numerical modelling to evaluate the efficacy of river processes and flood management interventions (specifically natural flood management) at reducing flood risk. I have a track record spans multiple projects including CONVERSE (Community vision for resilient riverscapes; NERC funded), TIMBER (Managing riverine flood risk & habitat diversity with in-stream wood; NERC funded) in conjunction with independent research to explore the influence of underrepresented river processes in flood hazard estimation.

My contribution to this request for evidence focuses on the representation of river process and natural flood management to inform the “Strengthening flood resilience” topic. My key recommendations are to:

1)      Increase understanding of river processes and how these might change with climate change.

2)      Develop opportunities for devolved community-level funding for nature-based solution creation and monitoring.

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1. To what extent are current flood resilience assets and interventions fit-for-purpose and what are the strengths and weaknesses?

Rivers are dynamic; they change shape in response to incoming water and sediment supply, yet often the impact of the latter during a storm event is not considered fully in our evaluation of flood hazards. Sediment can accumulate upstream of river-blocking features such as bridges and weirs, and in confined channels dramatically increasing flood risk to properties by reducing the capacity of water that the channel can hold[1]. This happened in the village of Glenridding (Lake District) following the extreme event of Storm Desmond in 2015 where the channel was infilled with sediment and Glenridding Beck burst its banks[2].

Such extreme/prolonged rainfall is becoming increasingly more common due to climate change, however our understanding of the impacts of sediment transport during a storm event is limited. At the same time, flood resilience assets (such as dams) are being downgraded as their designed protection levels are outpaced by climate change impact. The condition of these assets is also deteriorating due to insufficient maintenance, further increasing the risk of failure and compounding flood hazards[3].

Recommendation: How sediment influences flood assets at different scales (local to catchment) must be assessed. This will vary with storm duration and rarity; however these behaviours must be understood to ensure we produce more accurate reflections of their effectiveness in response to changing climate. This will ensure that flood assets are resilient to climate change, and further our prioritisation of future maintenance schedules and approaches.

2. How appropriate is the current balance between 'green' nature-based solutions and 'grey' hard infrastructure resilience assets, and what adjustments, if any, are needed to improve it?

Nature-based solutions (NSB) can enhance flood resilience by increasing the volume of water that is stored out of the main river channel (offline storage)[4],[5]. Holistic catchment management approaches that utilise natural flood management can reduce downstream flood risk, however they should not be relied upon in isolation to protect valuable assets. However, NBS present opportunities for local community groups to connect with nature and take ownership over their local environment and to better understand their own risk to flooding. Through education, individuals will better understand how to respond to a flood scenario and be better prepared in an emergency. In addition, there is a lack of distributed data that is of “good enough” quality to inform our understanding of flood risk at smaller scales that can be used to inform forecasting.

Recommendation: Funding to facilitate community NBS installation, combined with schemes to promote monitoring of such interventions, should be prioritised to further i) community connection to their local environment, and ii) our scientific understanding of how NBS interact to reduce (or increase) flood risk.

January 2025

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