Consider suburban streams as hybrids: theoretical and methodological reflexion from the PARISTREAMs project

Suburban streams are often considered to be our least restorable ecosystems but they often constitute an important part of the hydrographic network in big cities and crucial environmental infrastructures for future urban development. Numerous studies have highlighted the dramatic hydrogeomorphological and ecological alterations due to the hydrological consequences of urban sprawl. Most often hydrogeomorphological research focuses on the consequences of urban development but has not integrated ordinary practices and long-term river system management that have significantly reshaped existing rivers. Thus, we propose an interdisciplinary approach integrating the biophysical and social dimensions and different temporal and spatial scales in the Paris urban area. The PARISTREAMs project considers suburban streams as hybrids, i.e. as fragments of the socio-nature and proposes a holistic approach to develop a socio-ecological knowledge.

The integration of paleoenvironmental and historical research place the current restoration projects on a trajectory of the fluvial systems that is essential to understand the role of legacies (sediment, infrastructures), that vary within a urban area, and to open the discussion on base line operation in a context of climate and metropolitan changes. The integration of hydrogeomorphological (channel geometry, riffle-pool sequence), biological (macroinvertebrates, fish) studies and research on social practices and associated representations is required to determine the contemporary dynamics because the banks of these streams are often subject to private ownership and to active management practices (river design, bank stabilization, riparian vegetation management, etc.). The first results obtained on two streams (< 20km long) support the final objective which is to propose a new hybrid methodology to have a holistic knowledge of suburban streams and to promote socio-ecological restoration according to their biophysical and social realities.