Onema

Diagnose physical alterations in rivers

Rivers are dynamic and mobile phenomena that constantly change between their source and mouth, as well as over time. Signs of a river in good health are a succession of turbulent, running and calm waters, diversified morphology (depth, width), natural banks, a high-quality substrate with connections to deeper waters, moving alluvial banks, lush and varied riparian vegetation, ecological continuity and open areas along the river. Good hydromorphological operation is conducive to biodiversity and the good ecological status of rivers.

For over a century, industrial and agricultural development as well as the various territorial-planning policies have resulted in modifications to the physical characteristics of rivers. Rectification of river beds, channelling, cutting of trees and artificialisation of banks, creation of levees and the construction of numerous dams and weirs have produced more uniform aquatic environments and depletion of aquatic biological populations. Today, alterations in the morphology and the hydraulic regime of rivers have become major factors in river degradation.

That is why the Water framework directive now requires that the hydromorphological characteristics of rivers be taken into account in evaluating the ecological status of surface waters. Onema is in charge of carrying out an evaluation of the morphology of rivers in France and setting up a national monitoring program. A diagnosis of malfunctions in aquatic environments will be the means to reveal the main physical alterations, look for the causes and indicate the best solutions for the necessary restoration work. This vast project will bring together a wide range of partners.