The role of recent tectonics and hydrological processes in the evolution of recurring landslides on the Danube's high bank in Dunaföldvár, Hungary

- We investigate river high bank movements by borehole tiltmeters and extensometer.
- Recent tectonic processes play an important role in the long-term slope stability.
- The effect of the ground water is greater than that of the river water level.
- Direct effect of the precipitation on the high bank movements is negligible.

There are high loess banks prone to landslide along the River Danube in Hungary. One of these is the high loess bank in Dunaföldvár, where several landslides occurred in the last decades. Quantitative relationships between the movements of the high loess bank and the variation of the water level of the River Danube, the ground water table, precipitation and temperature are investigated by two borehole tiltmeters and a vertical borehole extensometer. The twelve-year long observation from 2002 to 2014 made it possible to distinguish between the high bank movements due to slow recent tectonic and geomorphologic processes and the short-period (from hours to months) movements caused by hydrometeorological effects. The results revealed that besides geomorphologic processes recent tectonics can play an important role in the recurrence of landslides in the area. In the investigated period the total tilt of the high bank was 162 μrad in the SSE direction according to the geomorphologic and recent tectonic processes in the surroundings of Dunaföldvár. Investigations of the relationships between the high bank movements and the water level of the River Danube, ground water table changes and the precipitation revealed that the tilt magnitudes caused by the ground water table variations are two orders of magnitude greater than the tilts caused by the water level regime of the river and the direct effect of the precipitation on the high bank tilts can be disregarded.