Hydromorphological alteration isn't always a pressure
A hydromorphological alteration is only a pressure, in strict interpretation of the Water Framework Directive, if it reduces the biological quality of a river. A problem is that there is often no strong evidence that a particular alteration is a pressure on specific Biological Quality Elements. Weak indications may be sufficient for preventing certain new developments by the ‘precautionary principle’ of environmental management. A lack of strong evidence is problematic, however, when dealing with restoration of sites that are damaged already and subject to multiple stresses. Assuming a certain hydromorphological alteration to be the main or only pressure carries the risk of not achieving the restoration targets when removing the alteration. Planning of restoration thus requires thorough analysis and evaluation.