A free and stand-alone tool integrating geospatial workflows to evaluate sediment connectivity in alpine catchments

A free and stand-alone tool integrating geospatial workflows to evaluate sediment connectivity in alpine catchments S. Crema, L. Schenato, B. Goldin, L. Marchi, M. Cavalli CNR-IRPI

Outline The evaluation of sediment connectivity in alpine catchments Development of the tool for the assessment of sediment connectivity The better strategy to make the tool usable The better strategy to make the tool open to scientific improvements and customization Test application, results and remarks

Topography-based sediment connectivity index /1 Index for the spatial characterization of sediment connectivity developed by Cavalli et al. (2013) following the approach by Borselli et al. (2008) Topography-based index aims at evaluating the potential connection between hillslopes and features which act as targets (e.g. catchment outlet, roads) or storage areas (sinks, retention basin) for transported sediment (modified after Borselli et al., 2008) Borselli L., Cassi P., Torri D., 2008. Prolegomena to sediment and flow connectivity in the landscape: a GIS and field numerical assessment. Catena, 75(3), 268-277. Cavalli M., Trevisani S., Comiti F., Marchi L., 2013. Geomorphometric assessment of spatial sediment connectivity in small alpine catchments. Geomorphology, 188, 31-41.

Flow direction D method (Tarboton, 1997) Slope S (m/m) S < 0.005 -> S = 0.005 S > 1 -> S = 1 GIT Geology and Information Technology Topography-based sediment connectivity index /2 Weighting factor W Related to the impedance to water and sediment fluxes; C factor of USLE RUSLE in the original model; Replaced by a roughness index (Cavalli et al., 2008). High W : Low roughness and low impedance to fluxes Low W : High roughness and high impedance to fluxes W 1 RI max RI 0.001 W (m/m) ranges from >0 to 1

Implementation: strategy and target Assessment of the need for such a tool (free, open source and GIS independent) Different stakeholders interests: management authorities/scientific community (integration with available databases) Analysis of different applicable frameworks and selection of the most suitable developing environment

Implementation: features

Input DTM Use default W? (Cavalli et al., 2013) Yes Input neighborhood analysis size W computation No Input W No SedInConnect 1.0 Workflow All NaN flagged to target Use Sinks? Use Targets? Yes No Targets Yes Pre-process to flag targets Sinks Pre-process to exclude sink.draining areas Connectivity index computation Output IC

Gadria and Strimm catchments (Eastern Italian Alps) Lithology: mica-schist, gneiss, and phyllite. Land use: coniferous forest, mountain grassland, bare rock and debris. Annual rainfall: around 500 mm in the valley floor, strong increase with elevation. Gadria: area 6.36 km 2, average slope 79.1%, range in elevation: 1394 2945 m. Strimm: area 8.5 km 2, average slope 61.8%, range in elevation 1394 3197 m. Application

Application: outlet/targets IC used to assess connectivity: 1. Hillslopes to outlet 2. Hillslopes to targets (e.g., channel network)

Application: sediment dynamics

Final Remarks The need for such a tool is being verified by the increasing interest in its usage Stakeholders are interested in a fast and simple connectivity assessment to give management priorities integrating the analysis with information on sediment availability Encouraging feedbacks from scientific community are pushing towards a continuous improvement (Cost action: Connecting European connectivity research) The testing of the tool permitted to compare its performance with equivalent GIS workflows and to analyze connectivity variability in relation to the sediment dynamics

Thanks for your kind attention! Is it a sink or a target? Photo by: H. Kross