A toolkit for identifying and measuring physical streams features from high resolution DEMs and digital image

In fluvial dynamics remote sensing using airborne LiDAR (Light Detection and Ranging) may provide an alternative basis for identifying and measuring physical-geomorphological stream features that are traditionally recorded by field surveys. The ability to remote sense bankfull elevations was of particular interest in this study because bankfull mapping depends on topographic indicator. Bankfull is defined as the elevation at which flow spills onto the floodplain. In order to objectively define the bankfull elevation, we plotted the hydraulic depth as function of flow height for each cross section. The local maxima values indicate a sudden increase in flow width where water spills across floodplain. Such approach have been used to create a GIS tool that runs as plugin in QGIS software and provides as result a series of river indices (sinuosity index, braiding index, bankfull channel width, formative discharge) very helpful for fluvial geomorphologists and the polygon map of the bankfull limits. The algorithm was applied on a reachs of River Paglia an Umbrian rivers (in central Italy) affected by a strong disequilibrium.