The Story of a Steep River: Causes and Effects of the Flash Flood on 24 July 2017 in Western Norway

Flash floods can cause great geomorphological changes in ephemeral fluvial systems and result particularly severe damages for the unprepared population exposed to it. The flash flood Storelva river Utvik (western Norway) on 24 July 2017 was witnessed documented. This study assessed causes effects of provides valuable information calibration validation future modelling studies. flooded area at peak discharge, maximum wetted dry areas during entire event, critical points main flow paths were reconstructed using on-site post-event (i) visual documentation, such as photographs videos, (ii) aerial surveying, orthophotographs laser scanning, lowermost reach. steep longitudinal slope together with loose material forming valley riverbed contributed a large amount sediment transport this extreme event. Steep rivers have very short response times hydrologic conditions, which calls exhaustive monitoring data collection case events, well tools that emulate hydro-morphodynamics observed events flood.