Sensitivity analysis of environmental changes associated with riverscape evolutions following sediment reintroduction: geomatic approach on the Drôme River network, France

The present paper aims to put into practice a conceptual framework for gravel-bed river sustainable management previously proposed by Pont et al. [(2009) Conceptual framework and interdisciplinary approach for the sustainable management of gravel-bed rivers: the case of the Drôme River basin (SE France). Aquatic Sciences, 71 (3), 356–370] for the Drôme River Basin (France). It tests the capacity of the functional sector concept (Petts, G.E. and Amoros, C., 1996. Fluvial hydrosystems. Springer) when used to assess the risks of environmental changes. The application of this concept is illustrated by examples focusing on the potential impacts of sediment replenishment on functional sector diversity used as a proxy of habitat diversity, and on trout distribution at a network scale. We used remote sensing and Geographic Information System (GIS) methods to produce original data. A cluster analysis performed on the components of a principal component analysis established a functional sector typology based on channel planform parameters. We calculated an index of present and 1948 functional sector diversity for the entire channel network to highlight past evolutions. A sensitivity analysis was then performed to predict changes in functional sector diversity resulting from defined options of sediment reintroduction through planned forest removal. A similar procedure was developed to evaluate likely changes in brown trout distribution resulting from the impacts of the actions on canopy cover and summer water temperature. The methodological procedure is described, as well as the different assumptions made to move from a theoretical framework to a more practical one. Two examples are used as pilots to evaluate the value of a sensitivity analysis approach based on functional sector types (FSTs) to test management actions aimed at improving aquatic ecology. Limitations and potential improvements are then discussed.

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