An open platform version of the Fluvial Corridor Toolbox with new functionalities to map nested floodplain envelops at the network scale

Fluvial geomorphology provides an integrative space-time framework to target actions for risk mitigation, water resource preservation, and biodiversity and landscape conservation. Geomorphic data provides support critically important knowledge on stream condition, adjustment processes and sensitivity to change. Multiscale frameworks are needed to organize knowledge into useful usable and usable useful information. To move towards a more river rehabilitation or conservation strategy, a planning effort is needed at the regional or network scale, so called upscaled geomorphology, to provide large spatial datasets and new environmental monitoring facilities. This new emphasis on spatial planning resonates also with the concept of “green infrastructures” as a mean to protect fluvial corridors and identify opportunities to restore lateral connectivity and floodplain functionalities, thus providing ecosystem services such as flood expansion zones or better functioning ecological networks.

The development of a new version of the Fluvial Corridor Toolbox (FCT), following the work done by Alber and Piégay (2011) and Roux et al. (2015), started as an effort to implement port the ArcGIS code to the QGis platform for promoting open science and sharing our tools with river practitioners. The initial version of the FCT provided a spatial framework to produce metrics at a fine scale and a disaggregation-aggregation procedure to delineate floodplain functional units along a channel network. The new version of the FCT has been completely rewritten and incorporates ideas from Nardi et al. (2018) and Clubb et al. (2017) for improving the calculation of riverscape feature heights above the water level and delineate floodplain through the river network. We also borrowed the concept of swath profiles from Hergarten et al. (2014) as the basis of a new raster-based approach to characterize floodplain features on cross-sections. These new functionalities are based on high resolution DEM and landcover data to produce different floodplain envelops. Finally, we implemented tiled processing of very large raster datasets after Barnes (2016, 2017). This new version of the FCT also provides a lightweight framework for developing new processing toolchains/workflows. We successfully processed 5 m resolution landcover data over the entire (French) Rhone basin and used these layers to highlight the FCT interest. The new workflows are suitable for working at large network scale and are reproducible. 

Further perspectives include an integration of such data and some FCT functionalities in online regional observatories with a visualization interface showing raw data on cross-sections and long profiles and synthetic patterns at the network scale allowing to compare target reaches with regional references.