River engineering

Scotland's rivers have been modified by people in many ways over a long period of time.  Many rivers have:

• been dammed to enable water abstraction for domestic and industrial use and to generate power
• had their banks reinforced to prevent the erosion of economically important land, such as that used for growing crops, and to prevent the undermining of roads and bridges
• been embanked to prevent flooding
• been extensively managed by fishery managers to promote fishing opportunities.

Many of Scotland's rivers have gravel beds and are constantly changing in response to heavy rainfall and other natural events.  Rivers have a lot of energy and need space to accommodate these changes. A change in energy in one part of a river may result in a change in another part of the river. 

Human interference can change the natural flow of a river and this may result in the need for additional, unplanned work as they adjust to these changes. For example, the creation of flood embankments in one part of a river may lead to worse erosion elsewhere as the power of newly constrained flood waters is transferred downstream.

Impact on biodiversity

Our rivers are part of Scotland's identity. They support internationally important species like the freshwater pearl mussel (Margaritifera margaritifera) and the economically valuable Atlantic salmon (Salmo salar). River engineering, for whatever purpose, has the potential to damage the long term viability of freshwater plants and animals by changing the availability and quality of physical habitat. For example, damming a river may prevent the migration of fish to and from spawning grounds and so cause a long-term reduction in fish populations, and badly planned or executed work may result in the siltation of salmon redds or the smothering of freshwater pearl mussels.

There is a lot of evidence to show that we need to work with and accommodate rivers if we are to look after nature. The need to do this is covered by the Water Framework Directive  , which is part of European legislation. The Water Environment and Water Services Act   brought this into Scottish law. Further legislation is expected to consider integrating natural flood management, e.g. the retention of natural flood plains and processes, in flood prevention schemes. This approach should benefit freshwater plants and animals.

Legislation is now a significant driver of the restoration of engineered river systems to their previously natural state and authorisation to undertake river engineering   must now be obtained from the Scottish Environment Protection Agency. The River Restoration Centre   is a focal point for the exchange of information and expertise relating to river restoration and enhancement in the UK and is supported by SNH. The Scottish Environment Protection Agency is responsible for administering the Water Environment Restoration Fund  . This funding from the Scottish Government seeks to restore the condition of Scotland's water environment and to support partnership projects with third parties. Scottish Natural Heritage also offers support through its Grant Programme.