Terrain attributes of earthquake‐ and rainstorm‐induced landslides in orogenic mountain Belt, Taiwan

Intense precipitation or seismic events can generate clustered mass movement processes across a landscape. These rare events have significant impacts on the landscape, however, the rarity of such events leads to uncertainty in how they impact the entire geomorphic system over a range of timescales. Taiwan is steep, tectonically active, and prone to landslide and debris flows, especially when exposed to heavy rainfall events. Typhoon Morakot made landfall in Taiwan in August of 2009, causing widespread landslides in southern Taiwan. The south to north trend in valley relief in southern Taiwan leads to spatial variability in landslide susceptibility providing an opportunity to infer the long‐term impact of such landslide events on channel morphology. We use pre‐ and post‐typhoon imagery to quantify the propagating impact of this event on channel width as the debris is routed through the landscape. The results show the importance of cascading hazards from landslides on landscape evolution based on patterns of channel width (both pre‐ and post‐typhoon) and hillslope gradients in 20 basins along strike in southern Taiwan. Prior to Typhoon Morakot, the river channels in the central part of the study area were about 3–10 times wider than the channels in the south. Following the typhoon, aggradation and widening was also a maximum in these central to northern basins where hillslope gradients and channel steepness is high, accentuating the pre‐typhoon pattern. The results further show that the narrowest channels are located where channel steepness is the lowest, an observation inconsistent with a detachment‐limited model for river evolution. We infer this pattern is indicative of a strong role of sediment supply, and associated landslide events, on long‐term channel evolution. These findings have implications across a range of spatial and temporal scales including understanding the cascade of hazards in steep landscapes and geomorphic interpretation of channel morphology. Copyright © 2018 John Wiley & Sons, Ltd.

Section: Field Areamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

Landslides control the spatial and temporal variation of channel width in southern Taiwan: Implications for landscape evolution and cascading hazards in steep, tectonically active landscapes

Yanites

Mitchell

Bregy

et al. 2018

“…Its impact on landsliding has been reported in hundreds of publications (e.g. Intensive seismic waves shook the whole island of Taiwan and caused 419 km 2 of landslides, or 1.6% of the island's total mountainous area (Huang et al, 2017). Intensive seismic waves shook the whole island of Taiwan and caused 419 km 2 of landslides, or 1.6% of the island's total mountainous area (Huang et al, 2017).…”

Section: Landslide Eventsmentioning

confidence: 99%

“…Most landslides were located within areas with the mean horizontal peak ground acceleration (PGA) greater than 0.15 g or within the distances of 40 and 70 km from the epicenter and the surface rapture of the Chelungpu thrust fault, respectively (Khazai and Sitar, 2004). Most landslides were found on steep slopes (Huang et al, 2017) and on the lithology unit of Quaternary sedimentary rock and Neogene sandstone and shale (Khazai and Sitar, 2004). Most landslides were found on steep slopes (Huang et al, 2017) and on the lithology unit of Quaternary sedimentary rock and Neogene sandstone and shale (Khazai and Sitar, 2004).…”

Section: Landslide Eventsmentioning

confidence: 99%

“…Heavy precipitation associated with Typhoon Morakot started on August 7 and lasted until August 10, 2009 as strong south-westerly flows, with maximum wind speeds of~32 m/s, pushed against the Central Mountain Range (Lin et al, 2010;Yu and Cheng, 2013) (Figure 2b). Landslides occurred mainly within areas with one-day rainfall ≥ 600 mm/day and on the lithological units of sedimentary and low-grade metamorphic rocks (Huang et al, 2017). Landslides occurred mainly within areas with one-day rainfall ≥ 600 mm/day and on the lithological units of sedimentary and low-grade metamorphic rocks (Huang et al, 2017).…”

Section: Landslide Eventsmentioning

confidence: 99%

See 1 more Smart Citation

Controls of preferential orientation of earthquake‐ and rainfall‐triggered landslides in Taiwan's orogenic mountain belt

Chen

Chang

Wang

et al. 2019

Self Cite

Landsliding usually occurs on specific hillslope aspect, which may reflect the control of specific geo‐environmental factors, triggering factors, or their interaction. To explore this notion, this study used island‐wide landslide inventories of the Chi‐Chi earthquake in 1999 (MW = 7.6) and Typhoon Morakot in 2009 in Taiwan to investigate the preferential orientation of landslides and the controls of landslide triggers and geological settings. The results showed two patterns. The orientations of earthquake‐triggered landslides were toward the aspect facing away from the epicenter in areas with peak ground acceleration (PGA) ≥ 0.6 g and landslide ratio ≥ 1%, suggesting that the orientations were controlled by seismic wave propagation. Rainfall‐triggered landslides tended to occur on dip slopes, instead of the windward slopes, suggesting that geological settings were a more effective control of the mass wasting processes on hillslope scale than the rainfall condition. This study highlights the importance of the endogenic processes, namely seismic wave and geological settings, on the predesigned orientation of landslides triggered by either earthquake or rainfall, which can in turn improve our knowledge of landscape evolution and landslide prediction. © 2019 John Wiley & Sons, Ltd.

The effect of location and geometric properties of landslides caused by rainstorms and earthquakes

Qiu,

Su,

Tang

et al. 2024

Landslides triggered by rainstorms and earthquakes are prominent geological hazards that exhibit distinctive spatial and morphological characteristics due to diverse instability mechanisms. However, studies on differences between the two types of landslides remain limited. In this study, we explored differences in location and geometric properties between rainstorm‐induced landslides in Qinzhou, Longchuan and Fukuoka and earthquake‐induced landslides in Lushan, Iburi and Kaikōura. We normalized the location of landslides across the slope and quantified the landslide polygons using four geometric properties. Findings revealed that both location and geometric properties are specific to landslide type and differ between them. Earthquake‐induced landslides are more common near the ridge of a slope, while rainstorm‐induced landslides are more frequent in the valley or near streams. The quantitative analysis of geometric properties showed that earthquake‐induced landslides are generally larger and have a more compact, rounded and less complex shape. The two landslide types present different hazards, particularly in their runout zones, where dispersion of materials occurs. Insights from our quantitative approach serve as a critical foundation for informed decision‐making in emergency scenarios and contribute to enhancing landslide hazard management.