Abstract
This study uses three periods of airborne laser scanning (ALS) digital elevation model (DEM) data to analyze the short-term erosional features of the Tsaoling landslide triggered by the 1999 Chi-Chi earthquake in Taiwan. Two methods for calculating the bedrock incision rate, the equal-interval cross section selection method and the continuous swath profiles selection method, were used in the study after nearly ten years of gully incision following the earthquake-triggered dip-slope landslide. Multi-temporal gully incision rates were obtained using the continuous swath profiles selection method, which is considered a practical and convenient approach in terrain change studies. After error estimation and comparison of the multi-period ALS DEMs, the terrain change in different periods can be directly calculated, reducing time-consuming fieldwork such as installation of erosion pins and measurement of topographic cross sections on site. The gully bedrock incision rate calculated by the three periods of ALS DEMs on the surface of the Tsaoling landslide ranged from 0.23 m/year to 3.98 m/year. The local gully incision rate in the lower part of the landslide surface was found to be remarkably faster than that of the other regions, suggesting that the fast incision of the toe area possibly contributes to the occurrence of repeated landslides in the Tsaoling area.
Highlights
With the advent of high-resolution digital elevation model (DEM) data, modern remote sensing technology has been effectively used in erosion studies for landslides [1,2,3,4,5,6] and river channels [7,8,9].In particular, multi-temporal DEMs [10,11,12,13] can be directly used for monitoring and analyzing the terrain change
The present study showed that the airborne laser scanning (ALS) DEMs could be applied to the direct observation and measurement of the erosion gullies, greatly reducing the amount of time-consuming fieldwork, such as configuring erosion pins or cross section measurements
This study used the ALS DEMs from three different periods to interpret the gullies formed on the slope after the Tsaoling landslide
Summary
With the advent of high-resolution digital elevation model (DEM) data, modern remote sensing technology has been effectively used in erosion studies for landslides [1,2,3,4,5,6] and river channels [7,8,9].In particular, multi-temporal DEMs [10,11,12,13] can be directly used for monitoring and analyzing the terrain change. The methods for calculating the erosion rate include the cross section measurement method [15,16], the erosion pin method [17], radiometric dating [18,19,20,21,22,23,24,25], the river suspended-sediment discharge technique [26,27], dendrogeomorphological methods (based on tree-ring analysis from exposed roots) [28,29], interferometric synthetic aperture radar (InSAR) [6], Remote Sens. The cross section measurement, erosion pin, and the dendrogeomorphological methods are mainly adopted for single point measurements They are limited to inaccessible terrains and are not appropriate for acquiring the erosion pattern at the watershed scale. Radiometric dating is best for the time scale of thousands to millions of years, as it cannot reveal the influence of short-term events These techniques have specific applicable ranges for terrain change estimation, in terms of both the temporal scale and the spatial scale
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