The evolution of river restoration

The Four Rivers for LIFE project will be delivering river restoration works at a number of locations on the Teifi, Tywi, Cleddau and Usk rivers to restore habitat structure and function.

In this blog Four Rivers for LIFE Senior River Restoration Officer, Leila Thornton talks about why we need to understand our rivers natural processes before starting any restoration work.

The rivers Teifi, Tywi, Cleddau and Usk are classed as Special Areas of Conservation (SAC), which means they are of international importance for their wildlife and plants such as Atlantic salmon, lamprey, shad, otter and water crowfoot.

Our rivers are coming under increasing strain, growing populations, climate change and the continued pollution of our waters means that our rivers are nowhere near the condition we want them to be.

All four rivers are currently in an unfavourable condition, so the aim of the Four Rivers for LIFE project is to restore the rivers’ natural habitat which has been lost over time.

The history of river restoration

Rivers and their floodplains have been affected by human activity for millennia. However, with the introduction of metal working in the Bronze Age from around 2,000BC to 700BC, swathes of land began to be cleared for farming and resource production.

This changed the environment so much that it caused rivers to completely change form. During the Roman occupation in Britain which lasted from AD 43 to AD 410, land began to be drained and rivers channelised and dredged to increase production on floodplains - a practice that continues to this day.

The Industrial Revolution put new pressures on freshwater environments causing a severe decline in water and sediment quality and a consequent loss of habitat and biodiversity.

First attempts to remedy these changes in the UK and Europe began in the early 1900s. Initially this involved small-scale artificial alteration to improve habitat but, over time, techniques have prioritised working with natural processes to restore river forms and processes at a catchment scale.

The 1992 European Commission (EC) Habitats Directive and the 2000 EC Water Framework Directive made river restoration a fundamental part of river management in the UK and Europe by requiring countries to improve the ecological status of their rivers.

What does restoring our rivers mean?

According to the River Restoration Centre (RRC), ‘river restoration’ is defined as the process of managing rivers to reinstate natural processes and restore biodiversity, providing benefits to both people and wildlife.

In their conference in April 2023 the RRC declared an ‘Action Strategy for River Restoration.’ In the strategy it stated a priority to ‘recognise habitat and natural processes being as important as water quality and quantity for healthy rivers.’

There are three principles at the heart of a well-functioning river system; good water quality, good habitat and functioning physical processes. When taken together, this  creates diverse wildlife groups. 

If any of these three principles of river health are damaged (water quality, physical processes, habitats), then the resilience and health of the whole system is reduced.

Therefore, by focusing on restoring physical processes, and by extension habitat, our project aims to improve the overall ecosystem and the resilience of the river system.

What is processed-based restoration?

Process-based restoration aims to restore the natural processes that sustain river and floodplain ecosystems.

Restoration actions are aimed at addressing the root causes of degradation and working with the rivers’ natural energy, in the form of flow, and sediment supply.

Using process-based river restoration can help to avoid common pitfalls such as creating habitat types that are outside of a site’s natural potential or attempting to create static habitats in a dynamic environment.

The principles listed below are from the RRC website and provide a starting point for our project when carrying out restoration work.

• Follow nature - messy is best and enhance natural features
• Rely on natural processes
• Deferring decisions to the system – allowing change
• Quantity of structure - larger number of smaller structures is better than one large structure
• Use natural, local building materials
• Self-sustaining systems are the solution

Why is understanding rivers important?

Every river behaves differently, and restoration projects require bespoke approaches and varying techniques dependent on the needs of that specific river environment.

To effectively restore a river to a more naturally functioning system, we need to understand what affects a river system and figure out what a river needs to be able restore natural form and function.

For our project, it’s crucial that we understand natural processes in a river catchment, and its connections with the land that it flows within, so we can determine whether the river restoration work will be effective and sustainable.

Any restoration techniques should aim to enhance, recreate, or emulate these natural processes to produce a more naturally functioning river.

Where do we start?

In order to identify sustainable river restoration opportunities, we need a detailed understanding of the morphology (meaning the study of a river channel shape and how it changes its shape and direction over time) and ecology of our rivers, their floodplains and the processes controlling sediment dynamics along the river and its tributaries.

Sediment encompasses everything from individual grains of clay, to river gravels and cobbles, right up to large boulders. A naturally functioning river will process these sediments and naturally sort them along its length with the energy available to it, creating a diverse range of habitats. Where there is an imbalance, for example, where there is a surplus of ‘fine’ sediment (clays and silts), valuable habitats can be lost as they become smothered.

We also need to understand the pressures acting upon those natural processes. For example, has the river has been dredged or straightened, have any man-made barriers like weirs or dams been built in the river, have wood or boulders been removed in the past, have banks been reinforced or flood embankments built, and are there are any constraints on sediment supply?

For some of our catchments, many of these issues have been considered in detail within strategic river restoration plans. For others we gather background evidence from other sources such as SAC Core management plans or River Basin Management Plans to help develop this understanding.

We also work closely with our partners the River Restoration Centre to access learning and best practice from other river restoration projects.

We survey the rivers and walk as much of their length as we can, and we also talk to farmers, anglers, landowners and other stakeholders who know their local river to try to appreciate the issues facing the river.

Every decision we make is rooted in evidence, the expertise of our colleagues and the people living in the communities that live along our rivers.

Where do we go from here?

Although process-based restoration takes time and understanding, in the long term this is what we must do.

To reach lasting solutions for the environment, wildlife and people we must look at doing things differently to what has been done in the past.

We must take the time to understand the needs of our natural environment on a catchment scale if we are to restore our rivers to the healthy, naturally functioning ecosystems they once were.

To find out more about Natural Resources Wales’s wider remit on regulating water quality click on this link

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