Hervé Piégay

Hervé Piégay

Research Director at the National Center for Scientific Research (CNRS)

Hervé Piégay, research director at the National Center of Scientific Research, got his Ph.D. in 1995 on the interactions between riparian vegetation and channel geomorphology. Since 1995 he is continuing his studies at the University of Lyon (Ecole Normale Supérieure of Lyon), France. He is a fluvial geomorphologist involved in integrated sciences for rivers, strongly interacting with hydraulic engineers, freshwater ecologists and practitioners (Water Agencies, Regions, Ministry of Ecology, French agency for biodiversity, Compagnie Nationale du Rhône, EDF). His research is focused on contemporary history of rivers and their catchments underlining human controls on environmental changes, wood in rivers, floodplain and former channel sedimentation and sediment transport. He is strongly involved in river management, planning and restoration, developing methodological frameworks and tools using GIS and remote sensing. He recently coordinated an international team on the redynamisation of the Rhine downstream from Kembs and a research program focused on feedbacks from monitoring programs conducted for assessing river restoration. Since 2010, he is the research leader of the scientific team working on the Rhône valley, being in charge of the Rhône Observatory of Human and Environment Interactions. He has contributed to more than 200 papers in peer-review journals and book chapters and has coordinated several edited books such as Tools in Fluvial Geomorphology – Handbook for ecologists and practitioners with M.G. Kondolf (2003, 2015), Gravel-bed rivers 6 : From process understanding to river restoration with H. Habersack and M. Rinaldi (2007) or fluvial remote sensing for science and management with P. Carbonneau (2012).

The keynote talk by Hervé Piégay will be on Wednesday, Sept. 11th at the auditorium TÜWI

Is Geomorphology really an issue in river restoration?

Since the end of the 1980s, River restoration becomes progressively a critical issue in river management. Improving river status was (and is still) a social expectation, translated in legal texts  and water policies. The Water Framework Directive in Europe is a good example of such evolution. We are progressively moving from a period where we fought rivers to improve our well-being to a period where we try to live with nature to avoid collapsing, promoting integrated strategies to sustain or be resilient to changes.

River restoration is therefore an emerging domain for which we had almost no real experiences and feedbacks, and monitoring effort is then a critical step to learn from our errors and improve our actions. Restoration, at least in its early stages, was mainly based on ecological knowledge. Why then should we consider geomorphology in river restoration?  The aim of this talk is therefore to explore and discuss this issue.

Successful restoration is often demonstrated by monitoring ecological indicators…. But the sustainability of restoration is also a condition of success, on which geomorphology can say something. Some examples from the Rhône restoration implemented in the mid 1990’s and still monitored will serve to illustrate the purpose.  Some rivers are not static but responsive, sensitive and can react to restoration so that after a few years the (re)created ecological habitats are not always the ones we expected. Once again geomorphology can provide knowledge to assess restoration actions that can be appropriate, determine if it is meaningful to play with forms (habitats) or processes, to promote active or passive restoration. Geomorphology is then useful for diagnosing rivers, understanding how they are changing and also why evaluating their current behavior and determining if we can mimic past functioning or imagine a new one based on these new conditions. A large numbers of rivers are “novel ecocomplexes” that cannot recover their past conditions. Restoration is still very opportunist, we restore reaches for which local stakeholders are motivated to act, without evaluating all the problems existing at a regional or national scale to target priorities, and without taking into account river responsiveness. These different points will be illustrated by a series of examples from Belgium, France and Italy.

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