Hydrological modelling of a slope covered with shallow pyroclastic deposits from field monitoring data

"A one-dimensional hydrological model of a slope. covered with pyroclastic materials is proposed. The soil. cover is constituted by layers of loose volcanic ashes and. pumices, with a total thickness between 1.8m and 2.5 m, lying. upon a fractured limestone bedrock. The mean inclination. of the slope is around 40, slightly larger than the friction. angle of the ashes. Thus, the equilibrium of the slope, significantly. affected by the cohesive contribution exerted by soil. suction in unsaturated conditions, may be altered by rainfall. infiltration. The model assumes a single homogeneous soil. layer occupying the entire depth of the cover, and takes into. account seasonally variable canopy interception of precipitation. and root water uptake by vegetation, mainly constituted. by deciduous chestnut woods with a dense underbrush growing. during late spring and summer. The bottom boundary. condition links water potential at the soil–bedrock interface. with the fluctuations of the water table of the aquifer located. in the fractured limestone, which is conceptually modelled as. a linear reservoir. Most of the model parameters have been. assigned according to literature indications or from experimental. data. Soil suction and water content data measured. between 1 January 2011 and 20 July 2011 at a monitoring. station installed along the slope allowed the remaining parameters. to be identified. The calibrated model, which reproduced. very closely the data of the calibration set, has been. applied to the simulation of the hydrological response of the. slope to the hourly precipitation record of 1999, when a large. flow-like landslide was triggered close to the monitored location.. The simulation results show that the lowest soil suction. ever attained occurred just at the time the landslide was triggered,. indicating that the model is capable of predicting slope. failure conditions."