## 2 Methodology & Case Study
### Case Study  
The proposed real-time monitoring systems with automated instrumentation, which allows for remote observations to be collected wirelessly, have been of great value in monitoring landslide-triggering under the impact of precipitation and soil moisture dynamics. However, the limitation of such a system is that it is suitable for monitoring and early warning for shallow landslides, thus this system can only have a superficial record of variables. In this study, this system was tested and established on a real landslide-prone slope in the Wenchuan earthquake region, China. The in situ monitoring slope is located in the catchment of the Yindongzi valley in Dujiangyan County, in the central part of Sichuan Province (Figure 3). The monitoring catchment is situated in the subtropical humid monsoon climate zone, with an annual average temperature of 16.7\({}^{\circ}\). The annual average rainfall is more than 1200 mm. Precipitation is mostly concentrated in the period from May to September. The landform of the Yindongzi valley can be categorized into middle mountains, the elevation ranges from a minimum of 1030 m above sea level (a.s.l.) to a maximum of 2050 m a.s.l. with about 1000 m height difference along a 2500 m gully length. The strata exposed are from the Proterozoic era, which include igneous rocks, andesitic rocks and granite. The slope failure was triggered by the Wenchuan earthquake and is composed of deeply weathered granite and andesitic gravel and sand. The total volume of this landslide is about 500,000 m\({}^{3}\). After the Wenchuan earthquake, the landslide's body was remobilized and transformed into debris flows during subsequent rainstorms. These storms exceeded 130 mm over 24 h on 13 August 2009, 17 July 2010 and 9 July 2013 respectively. The Yindongzi landslide and the secondary debris flows threaten the totally rebuilt community residences of Lianhe Village, Dujiangyan County.  
A total of 15 sets of equipment were installed to collect real-time data for the Yindongzi landslide (Figure 3). In May 2014, a real-time monitoring system of multiple parameters including inclination, rainfall, ground vibration and hydrologic measurements were installed in the shallow subsurface of the Yindongzi landslide site in Dujiangyan. In this landslide, 3 soil moisture sensors were installed with NO. 9, 10 and 12 tilt sensors. In particular, the NO. 12 moisture sensors were installed with a tensiometer to study the hydraulic characteristics of the soil. Moreover, a ground vibration detector was installed on 24 April 2016, to record the number of responses when ground vibrations overpassing  
Figure 3: Location of the in situ monitoring site, which is conducted on a natural landslide site in Yindongzi valley, Dujiangyan County, Chengdu City, Sichuan Province, China.  
the acceleration threshold of 0.375 g were detected. These may possibly have been induced by the bounce and tumble motion of the landslide against the underlying ground (Figure 3). Although the installed sensors were at risk of break-down due to the extreme humidity and temperature in the field, most of the sensors have worked normally with limited maintenance. The monitoring system has been collecting real-time data and long-term changes of precipitation and soil moisture at the Yindongzi landslide site from 21 May 2014 to 22 August 2017. However, our monitoring tilt sensor has not observed any positive displacements during the monitoring period, nor any changes in inclination. As a result, the tilt data are not shown and discussed in this paper.