Links between Landslides, Rainfall and Sediment Discharge around Langang and Chishan catchment
Date Issued
2012
Date
2012
Author(s)
Chang, Jui-Ming
Abstract
This research focus on landslides distribution, sediment discharge, rainfall energy and seismometers signal. During the period 2005-2011, we investigated rainfall-induced landslides along Chishan catchment of southern Taiwan and Lanyang catchmen of Northern Taiwan from different typhoon events.
The investigated result landslide ratios was 1.7% in Typhoon Kamegi, 7.27% in Typhoon Morakot, 5.61% in Typhoon Fanapi and 4.5% in Typhoon Nanmadol. After Typhoon Morakot, the decrease of landslide ratio reveals the slope reclamation little by little. The landslide ratios ranged from 1.07% to 1.32% in Lanyang catchments. In downstream area the landslide ratios ranged from 0.29 % to 0.6 %. In upstream area the landslide ratios ranged from 2.12 % to 2.52 %. Landslides distribution gathered in upstream area. On average the sediment discharge of Chishan catchment was 1,797 t/km2/yr and of Lanyang catchment was 10,395 t/km2/yr. Sediment concentration was 2.52 times after Typhoon Morakot and 5.7 times after Jiaxian earthquake in Chishan catchment. Discharge suspended sediment to the ocean at hyperpycnal concentrations (>40 kg/m3). During the period 1980–2010, 4 hyperpycnal flow events detected in Lanyang catchment When the accumilated rainfall reached 360 mm can induce it probably. The recurrence interval for a hyperpycnal flow was about 7 years.
During typhoon Morakot 12 landslides were detected in Southen Taiwan. Landslide areas from 0.3 km2 to 2.7 km2 were detected by using signal analysis from seismometers. Our findings point out that the accumulates precipitation ranges from 712 mm to 1967 mm if rainfall-triggers a landslide area (more than 0.3 km2). It implied that using broadband stations to analysis rainfall conditions for big landslide would be a potential tool.
The investigated result landslide ratios was 1.7% in Typhoon Kamegi, 7.27% in Typhoon Morakot, 5.61% in Typhoon Fanapi and 4.5% in Typhoon Nanmadol. After Typhoon Morakot, the decrease of landslide ratio reveals the slope reclamation little by little. The landslide ratios ranged from 1.07% to 1.32% in Lanyang catchments. In downstream area the landslide ratios ranged from 0.29 % to 0.6 %. In upstream area the landslide ratios ranged from 2.12 % to 2.52 %. Landslides distribution gathered in upstream area. On average the sediment discharge of Chishan catchment was 1,797 t/km2/yr and of Lanyang catchment was 10,395 t/km2/yr. Sediment concentration was 2.52 times after Typhoon Morakot and 5.7 times after Jiaxian earthquake in Chishan catchment. Discharge suspended sediment to the ocean at hyperpycnal concentrations (>40 kg/m3). During the period 1980–2010, 4 hyperpycnal flow events detected in Lanyang catchment When the accumilated rainfall reached 360 mm can induce it probably. The recurrence interval for a hyperpycnal flow was about 7 years.
During typhoon Morakot 12 landslides were detected in Southen Taiwan. Landslide areas from 0.3 km2 to 2.7 km2 were detected by using signal analysis from seismometers. Our findings point out that the accumulates precipitation ranges from 712 mm to 1967 mm if rainfall-triggers a landslide area (more than 0.3 km2). It implied that using broadband stations to analysis rainfall conditions for big landslide would be a potential tool.
Subjects
landslide
rainfall kinetic
sediment discharge
landquake signal
Type
thesis
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