Papers by Toshiaki Sammori
Landslide News, Jun 1, 1998
Journal of the Japanese Forest Society, 2005
Journal of the Japan Society of Erosion Control Engineering, 1993
Journal of the Japan Society of Erosion Control Engineering, 1995
Journal of the Japan Society of Erosion Control Engineering, 2012
Journal of the Japan Society of Erosion Control Engineering, 2013
Journal of the Japan Society of Erosion Control Engineering, 1995
Journal of the Japan Society of Erosion Control Engineering, 1995
Journal of the Japan Society of Erosion Control Engineering, 2012
Journal of the Japan Society of Erosion Control Engineering, 2013
Journal of the Japanese Forest Society, 2005
Hydrological Processes, 2004
Suspended solids (SS) discharge from a tropical rain forest was observed at the Bukit Tarek Exper... more Suspended solids (SS) discharge from a tropical rain forest was observed at the Bukit Tarek Experimental Watershed in Peninsular Malaysia in order to elucidate mechanisms of SS production and transport. Peaks of water discharge and electrical conductivity (EC) lagged further behind rainfall peaks than did dissolved oxygen (DO), indicating that the discharge in the early stage of a storm is mainly formed by rain water with high DO. Stream water showing a high value of EC originating from subsurface water formed the main storm flow and lagged behind the rainfall. SS concentrations rose to a peak quickly and, like DO, the peak preceded that of water discharge. A clockwise hysteresis loop in the relationship between SS and water discharge exists, and the magnitude of hysteresis loop is in proportion to storm size. The values of SS concentration correlate positively with the values of rainfall intensity on logarithmic axes. The time intervals between peaks of rainfall and SS concentrations are assumed to be a delivery term expressing distance from sediment source to measuring point. Immediate transport of SS from the source to the sampling site, the short time gap between the peaks of rainfall and SS concentrations, and the high rate of infiltration on the hillslope suggest that the sources of high SS concentrations are located close to the stream. The calculated source area is located at a gentler part of the stream, where wet riparian areas exist. The strong relationship between water discharge and SS concentration during the small storm proves that the source areas of SS and water were the same. In contrast, the source area of SS disappeared when rainfall ceased, whereas the source area of water discharge was still expanding in the larger storm. These phenomena may produce clockwise loops in the SS concentration-water discharge relationship.
Engineering Geology, 2000
... Author Keywords: Experimental studies; Fluidization; Landslide; Numerical simulation; Physica... more ... Author Keywords: Experimental studies; Fluidization; Landslide; Numerical simulation; Physical models; Sensitivity analysis. ... travels as a mass on the slope and analyzes the balance between gravity ... However, Kobayashi (1991) posed a question of what is the continuous source ...
Engineering Geology, 2002
An almost real-size slope model was used to study the generation process of landslide fluidizatio... more An almost real-size slope model was used to study the generation process of landslide fluidization during torrential rain. Experiments were conducted by filling an inclined flume with loose sand and spraying water over the flume with a rainfall simulator to induce the sand to collapse. Both the movement, volumetric strain and the pore water pressure of the sand were monitored throughout the experiments, from the start of spraying to the cessation of the landslide. Our experiments showed the following. (1) Landslide fluidization caused by undrained sudden loading undergoes three stages: compaction of the sand layer by the sliding mass from upper slope, generation of excess pore water pressure in saturated zone, and induction of fast shearing. (2) Fluidization at the collapse source area also undergoes three stages: destruction and compaction of sand layer skeleton by outbreak of shearing, increase of pore water pressure in saturated zone, and shift to fast shearing. But these three stages take place almost simultaneously.
Journal of Forest Research, 1997
Soil physical properties and water movement within soil were investigated using dyes in a tropica... more Soil physical properties and water movement within soil were investigated using dyes in a tropical rain forest, the Bukit Tarek Experimental Watershed of Peninsular Malaysia. The saturated hydraulic conductivity (Ks) decreased with increasing soil depth. The K~ values were higher than those reported for other tropical soils. The geometric means of the Ks values ranged from 4.69 • 10-3 (80 cm) to 4.07 • 10-2 cm s-1 (10 cm). This suggests saturation overland flow may not be dominant but that subsurface flow must play an important role in stormflow generation. The shapes of the soil moisture characteristic curves resembled those of forest soils which have large changes in volumetric water content at pressure heads < 30 cmHzO. The relatively high conductivities were due to the presence of a porous zone of decomposed root channels which existed continuously in vertical direction. Besides decayed roots, living roots also encourage preferential flow in vertical and lateral (downslope) directions. Termite activities may also form water flow pathways in tropical regions. These detailed results help us analyze water flow within the soil in tropical rain forests.
Journal of Forest Research, 1997
Field observations were conducted at Bukit Tarek Experimental Watershed in Peninsular Malaysia to... more Field observations were conducted at Bukit Tarek Experimental Watershed in Peninsular Malaysia to investigate the relationship between rainfall-runoff responses and variation in soil moisture in a tropical rain forest. Stormflow depended strongly on the antecedent wetness as ...
The Iwate-Miyagi Nairiku Earthquake in 2008, which occurred at 8:43 JST, 14, May, 2008 inland of ... more The Iwate-Miyagi Nairiku Earthquake in 2008, which occurred at 8:43 JST, 14, May, 2008 inland of Tohoku region, caused a lot of landslides on mountain hill slopes near the epicenter. We analyzed the influences of geology, topography etc. on occurrence of landslides with Geographical Information System (GIS) in this report. We extracted and plotted the landslides with aerial photographs and satellite visible light images of ALOS which are taken after the earthquake. The numbers and area of landslides were 10,751 and 13.576 square kilometers, respectively. We obtain conclusions as follows; 1. Most of landslides occurred on hanging walls within fifteen kilometers from the seismogenic reverse fault; 2. fragile strata of volcanic deposits strongly affected the landslide occurrence; 3. The landslides occurred near the geological boundaries; 4. A cap rock type of landslides, with strata combination of welded tuff in upper and lacustrine deposit in lower, is conspicuous on steep rim slopes ...
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Papers by Toshiaki Sammori