Restoration of fluvial connectivity through dam removal

 

Restoration of fluvial connectivity through the removal of structures responsible for impoundment is an increasingly considered option to mitigate environmental impacts of river engineering. In Europe, dam and weir removal has become a commonly proposed restoration strategy, particularly as a high density of structures exists, and morphological pressures are considered to be one of the most important reasons for why ecological status of water bodies are failing under the Water Framework Directive. In many cases the small-scale historic dams and weirs, e.g. built for milling, no longer fulfil the purpose for which they were originally constructed.

In North America, dam removal is a popular restoration option under some scenarios, especially when decisions to do so are supported by other non-ecological factors, such as safety and the economic and legal considerations of relicensing, renovation and maintenance. ICER has been involved in providing advice on the potential to remove the Mactaquac Dam on the Saint John River in New Brunswick, Canada.


In developing nations, dam removal has not yet become a commonly considered river restoration strategy. Despite this, ICER are supporting the Federal University of Lavras, Brazil, to investigate the potential of removing the Pandeiros Dam on the Pandeiros River, a tributary of the São Francisco River.  Construction of the dam was completed in 1958.  However, the reservoir rapidly suffered from excessive sedimentation and has now been decommissioned.  Removal is likely to be a viable option. Working in close collaboration with Professor Paulo Pompeu at the Federal University of Lavras, ICER is helping to conduct detailed baseline surveys and develop predictions of sediment transport scenarios following a future removal. As part of the project, ICER is also providing advice on the use of stable isotope analysis to investigate changes in food web dynamics as a result of dam removal; engineering options for method of dam removal; and prioritisation methods of watershed scale dam removal in Minas Gerais state.
If this dam removal goes ahead, it will likely represent the first project of its kind in South America.

 

Media: 

 

Meeting of International experts, including ICER’s Paul Kemp, to discuss removal of the Macaquac Dam (Canada)

The Pandeiros Dam (Brazil), which is being assessed for the feasibility of removal