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Dynamic characteristics of extreme superelevation of debris flows observed by laser profile scanners in Sakura-jima volcano, Japan
Takahashi, Yuya Fujimura, Naoki Akita, Hiromi Mizuno, Masaki
Takahashi, Yuya
Fujimura, Naoki
Akita, Hiromi
Mizuno, Masaki
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2019
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Abstract
Supercritical flows in natural open channel show very complicated behavior due to shockwaves, roll waves, and superelevations. Traces of debris flows often show large difference in height at inner and outer sides of curved channels, and not only that, superelevation of debris flow is larger than that of pure water. This behavior of debris flow may cause underestimation of channel section design or unexpected bank erosion. Therefore, accumulation of observation data is important to estimate hydraulic characteristics of debris flows at curved channels. We conducted continuous field observations at Sakura-jima volcano, Japan, introducing laser profile scanners (LPSs) to acquire surface geometry of debris flows, especially superelevation at curved channels. The LPS can measure distance from sensor to obstacles with sufficiently high resolution to document superelevations and spillway flow profiles both in space and time on a survey line. A debris flow that occurred at Arimura River, Sakura–jima volcano on January 17, 2018 is well documented by LPSs. Data from the debris flow compared with coefficient in current model, which indicates traction/viscosity and potential superelevation of the debris–flow front is under-predicted assuming the flow is super-critical pure water flow.
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