Small slope tilts caused by meteorological effects and vital processes of trees on a wooded slope in Hidegvيz Valley, Hungary

Long-term measurements were carried out to investigate the relationship between ground tilts and variations of meteorological (temperature, precipitation) and hydrological (soil moisture content) parameters in the area of the Sopron Mountains, on a wooded slope of the Hidegvíz Valley, Hungary. The connection between surface tilts and the vital processes of the trees was also studied on the basis of the reference evapotranspiration calculated for the study area. Long- and short-term variations were separated. A long-term ground temperature change of 1 °C caused a 4 μrad tilt in the SE direction. Short-term temperature effects can be neglected. The fluctuation of temperature around the freezing point caused tilts of about 10 μrad °C− 1. The soil water content variation had the largest effect on the ground tilt (0.5 μrad mm− 1). Its contribution to the total ground tilt in the investigated period was about 70 μrad (65% of the total tilt of 107 μrad) toward the SSE. The contribution of the wind speed to the ground tilt was about 20 μrad m s− 1 toward the SSE depending on the water content of the soil. The wind did not cause a permanent ground tilt. The magnitude of the daily tilt variations in the active growing period of trees, from March to October, is 1–2 μrad while in the dormant period (with no canopy) the tilt variations were less than 0.4 μrad. The admittances between the evapotranspiration and the ground tilts were 0.3–0.5 μrad mm− 1 and 0.1–0.2 μrad mm− 1 in the active and dormant period of the trees, respectively. These small effects superimposed on each other can significantly contribute to slope failures. The results of this study provide information which can be useful in the modelling of landslide movements and for the mitigation of landslide hazards.