Assessing the role of riparian vegetation and land use on river ecological status using remote sensing and spatial modelling
Résumé
Preserving or restoring the ecological quality of aquatic ecosystems is a major objective of Water Framework Directive. A pending question deals with the gain in river ecological status indicators that could be allowed by restoring riparian tree vegetation. In order to quantify in a statistically relevant way the role of riparian vegetation on river ecosystems, a regional approach is required that mobilizes three complementary fields of research : (1) the use of very high spatial resolution satellite imagery to map river corridor land use and riparian vegetation along large river networks ; (2) the design and quantification of synthetic spatialized indicators of river corridor land use; (3) the development of pressures/state spatialized models that quantify the relation between river corridor land use indicators and river water bodies ecological status indicators. The corresponding methods were developed and implemented on various river basins, particularly over lower Normandy river networks (6000 km long; 157 ecological stations). Results show for instance that in this region, changing the local land use along a river from agriculture to forest (over a buffer 1km long and 30m large on both sides of the river) allows in average to increase by 0.3 points the river ecological status indicators (EQR-IBGN between 0 and 1). Such results are of high interest for decision-makers that can estimate the interest of investing in restoration strategies by anticipating their effect in terms of Water Framework Directive standards.
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