A framework to quantify 50-100 year human-driven channel changes at regional level: the case of the Piedmont region, Italy

We derive characteristic Hydraulic Scaling Law (HSL) using a regional database of river geomorphic features. We investigate how Bankfull Channel Depth (eBCD), Active Channel Width (ACW), and Low Flow water Channel Width (LFCW) scale with flow discharge. The latter is here approximated with basin area through a regression based on available gauging stations. In doing so, we consistently link discharge with channel geometry features (eBCD, ACW, LFCW), continuously available from RS data along the river course. We then use historical information and external sources of information about channel reaches relatively unaffected by human pressure over a few decades to a century (measured in comparable geographical areas) to infer relatively Unaltered HSLs (rUHSL). Adopting rUHSL validated with available local historical evidence on channel geometry we are able to assess historical changes in channel geometry consistently over the entire region and within the studied temporal window. This methodology provides robust, novel and quantitative information about decadal to secular human-induced channel changes occurred at regional scale. This new layer of information enriches our ability to rationally address the assessment of past and future channel trajectories and to adapt future human developments in accordance to that.