Effect of antecedent rainfall conditions and their variations on shallow landslide-triggering rainfall thresholds in Sou
- PDF / 3,915,943 Bytes
- 14 Pages / 595.276 x 790.866 pts Page_size
- 62 Downloads / 209 Views
Suk Woo Kim I Kun Woo Chun I Minseok Kim I Filippo Catani I Byoungkoo Choi I Jung Il Seo
Effect of antecedent rainfall conditions and their variations on shallow landslide-triggering rainfall thresholds in South Korea
Abstract The intensity-duration (I-D) threshold is considered an effective indicator for landslides triggered by short-term highintensity rainfall and long-term low-intensity rainfall. However, previous studies have not considered the influence of antecedent rainfall. Herein, we analyzed hourly rainfall data for 613 shallow landslides that occurred from 1963 to 2018 in South Korea to obtain rainfall thresholds and investigated the effect of antecedent rainfall conditions on threshold variations. The I-D and IMAP-D, which is normalized by dividing I by mean annual precipitation (MAP), thresholds were determined to be I = 10.40D–0.31 and IMAP = 0.006D–0.26 (4 ≤ D (h) ≤ 84), respectively, at the 2nd percentile level through quantile regression analysis. These thresholds were lower than other local thresholds (i.e., excluding global and regional thresholds), suggesting that the southern region of the Korean Peninsula was more susceptible to rainfall-induced landslides. Although the effective length of antecedent rainfall was not presented herein, the I-D threshold of landslide-triggering rainfall was confirmed to be low for the absolute and/or calibrated antecedent rainfalls greater than event cumulative rainfall at 5, 7, 10, and 20 days prior to the event. Such differences in I can be greater at shorter durations; however, these differences gradually decrease as D increases, suggesting that they lose their effect as soil water content increases. The results of the current study can improve the understanding of the effect of antecedent rainfall conditions on landslide occurrence and should be further tested with respect to the hydrologic response of hillslopes by considering regional climate and local site conditions. Keywords Landslide . Rainfall . Threshold variation . Antecedent rainfall . Intensity-duration threshold . South Korea Introduction Landslides are natural phenomena that cause the erosion of the Earth’s surface, which often cause personal injury and property damage (Sidle and Ochiai 2006). South Korea has a high percentage of mountainous regions, and many residences and infrastructure are located in piedmont areas. In summer, the majority of the annual precipitation is concentrated over 4 months (June to September), which increases the potential risks of landslides. Therefore, it is critical to understand the factors that affect the probability of landslide occurrence in order to predict and prevent landslide damage. Among various factors affecting landslide occurrence, rainfall is the most widely recognized extrinsic landslide triggers (Wieczorek 1996). Rainfall triggers landslides by increasing pore water pressures, thereby causing a decrease in shear strength (Brand 1981; Terlien 1998). Particularly, heavy rainfall can quickly shift the slope from a marginally stable to an actively unsta
Data Loading...
