RiverZone started as a replacement for the ailing and unmaintained water level page on CKFiumi website and later merged with the Rivermap project.
The Riverzone webpage remains as a resource for the Italian kayaking community and as a way for me to experiment with new data (like, for example, per-river-section Point of Interests) and new UI approaches.
The Riverzone backend, merged with Rivermap, now powers both websites and the Restful API that other projects are leveraging to extract both station and river section data.
At the time of writing the combined database contains just shy of 1800 sections with river, name, coordinates, grades, classification, paddling length, duration, and, where available, calibrations.
Gradient is something we're working on using public Digital Elevation Models.