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Temporal and spatial variation of infilling processes in a landslide scar in a steep mountainous region, Japan
Citation:
IMAIZUMI, F., R. Sidle, A. TOGARI-OHTA, AND M. SHIMAMURA. Temporal and spatial variation of infilling processes in a landslide scar in a steep mountainous region, Japan. Earth Surface Processes and Landforms. John Wiley & Sons Incorporated, New York, NY, 40(5):642-653, (2015).
Impact/Purpose:
Article published in the journal, Earth Surface Processes and Landforms.
Description:
The duration of the soil-depth recovery needed for reoccurrence of landslides at a given site is much longer than the return period of rainfall needed to generate sufficient pore water pressure to initiate a landslide. Knowledge of the soil development rate in landslide scars is therefore necessary to evaluate return intervals of landslides. Spatial variation in the sediment flux at the Kumanodaira landslide scar in central Japan was investigated by field observations. Spatial distribution of the rate of change in soil depth was estimated using sediment flux data and GIS analysis. Observations revealed that the timing of sediment supply differed for shallow and deep soil layers. Near-surface soil movement (mostly dry ravel and some shallow soil creep at depths ≤0.1 m) measured in sediment traps was active in winter and early spring and was affected by freeze-thaw; deeper soil creep (i.e., >0.1 m), monitored by strain probes, was active in summer and autumn when precipitation was abundant. Sediment flux near the ground surface was estimated by a quadric function of slope gradient. Deeper soil creep was more affected by location, relative to the landslide scar, than by slope gradient. Our study indicated that the rate of soil development is high just below the head scarp of the landslide. Rugged terrain around the landslide scar became smoother with time due to degradation peripheral to the landslide ridge as well as aggradation below the head scarp.
