Links Between Channel Mobility and Habitats: On the Importance of Protecting a Mobility Space for Rivers

Anthropic riparian land use often leads to human interventions that limit channel mobility, such as bank stabilization. However, channel mobility is an important geomorphological and ecological agent that structures natural in-steam and riparian ecosystems, with migration of meanders being a patch-dynamic process responsible for the maintenance of a diversity of habitats. This study aims to 1) appraise river mobility for a 50 km-long reach of the Yamaska Sud-Est River, which runs from the Appalachian Mountains to the St-Lawrence lowlands in Quebec, and 2) assess links between channel mobility, geomorphological context, and the presence of related habitats. Channel mobility was measured from georeferenced historical aerial photos for the period 1950-2009. Sediment bars, oxbow lakes and log jams, three major elements for habitat diversity, were mapped along the river using high-resolution aerial photos, LIDAR and field data. A strong link between the presence of these habitats and mobility is revealed, but local geomorphological contexts create different mobility patterns responsible for specific habitats. The relevance of defining a protected corridor where bank erosion can freely occur is also discussed in the context of a broader concept of freedom space for rivers.