Continuous debris flow monitoring using DFLP and LVP on Sakura-jima Island

Abstract

Since 2010, numerous debris flows have occurred on Sakura-jima Island due to rainfall events that occurred after extensive ash deposition associated with volcanic activity. The study area included the Nojiri and Arimura rivers in the southwestern and southeastern parts of Sakura-jima, respectively. Debris flow monitoring systems consisting of loadcell and pressure sensor (DFLP) were installed to evaluate characteristics of moving weight and so on during debris flows. The systems were installed at the Arimura River No. 3 sabo dam in June in 2012 and at the Nojiri River No. 1 sabo dam in 2014. In addition, LVP (Load, Vibration and Pressure) sensors consisting of loadcells and accelerometers for measuring vibration and pressure were installed on the riverbed for debris flow detection. Modified LVP systems were installed at the Nojiri River No. 7 sabo dam in February in 2015, and at the Arimura River No. 3 sabo dam in October in 2016. Interesting characteristics of debris flows were obtained by the DFLP and LVP systems. The findings showed that the sediment concentrations of both the coarse and the suspended and liquid phases could be estimated by the DFLP systems, and several patterns of debris flows were observed by the LVP systems.