A simple and feasible process for using multi-stage high-precision DTMs, field surveys and rainfall data to study debris flow occurrence factors of Shenmu area, Taiwan

Abstract

Abstract. The occurrence of typhoon Herb in 1996 caused massive landslides in the Shenmu area of Taiwan. Many people died and stream and river beds were covered by meters of debris. Debris flows almost always take place in the Shenmu area during the flood season, especially in the catchment areas around Tsushui river and Aiyuzih river. Anthropogenic and natural factors that cause debris flow occurrences are complex and numerous. The precise conditions of initiation are difficult to be identified, but three factors are generally considered to be the most important ones, i.e. rainfall characteristics, geologic conditions and topography. This study proposes a simple and feasible process that combines remote sensing technology and multi-stage high-precision DTMs from aerial orthoimages and airborne LiDAR with field surveys to establish a connection between three major occurrence factors that trigger debris flows in the Shenmu area.

Evaluation of shallow landslide-triggering scenarios through a physically based approach: an example of application in the southern Messina area (northeastern Sicily, Italy)

“…Another drawback of the empirical rainfall thresholds is a general lack of spatial resolution. This aspect cannot be neglected if we consider that the terrain factors which control the onset of instability during a rainfall event can vary spatially to such an extent that, from a theoretical point of view, the rainfall threshold can be different for each landslide (Lo et al, 2012). Finally, further criticisms are based on the observation that it is not the amount of precipitation but the (largely unknown) amount of water that infiltrates and moves into the ground, and causes slope failure (Guzzetti et al, 2008).…”

Evaluation of shallow landslide triggering scenarios through a physically-based approach: an example of application in the southern Messina area (north-eastern Sicily, Italy)

“…where K s is the saturated hydraulic conductivity, H the average soil thickness (80 cm) and S y the specific yield (Grelle et al, 2014). If we consider that the investigated soil can be classified as loamy sand, the specific yield is assumed to be equal to 0.34, on the basis of typical values given by Johnson (1967) (also reported in Loheide II et al, 2005) for each soil textural class. With regard to the comparison between the numerical simulations and the landslide inventory map, Table 4 reports, as well as the number and relative percentage (P U ) of predicted unstable pixels (i.e., SF ≤ 1), the percentage of correctly pre- dicted landslide (P L ) and stable (P S ) pixels between 13:00 and 21:00 UTC.…”

“…Another drawback of the empirical rainfall thresholds is a general lack of spatial resolution. This aspect cannot be neglected if we consider that the terrain factors which control the onset of instability during a rainfall event can vary spatially to such an extent that, from a theoretical point of view, the rainfall threshold can be different for each landslide (Lo et al, 2012). Finally, further criticisms are based on the observation that it is not the amount of precipitation but the (largely unknown) amount of water that infiltrates and moves into the ground, and causes slope failure (Guzzetti et al, 2008).…”

Overview: Documentation and monitoring of landslides and debris flows for mathematical modelling and design of mitigation measures – outcomes of the EGU 2011, NH session

“…The paper by Lo et al (2012) shows how different kinds of information and data should be gathered and implemented to allow a global understanding of the debris flows processes, and facilitate decision making. The paper analyses the way in which DTMs, field surveys and rainfall data can be used for the study of debris -low occurrence factors in the Shenmu area, Taiwan.…”