Long-term relationship between landslide occurrences and precipitation in southern Lower Saxony and northern Hesse

A dataset with information about 394 landslide events between 1901 and 2016 is used for the analysis of the long-term relationship between landslides and precipitation in southern Lower Saxony, northern Hesse and the surroundings. The present study investigates the relationship between landslides and annual precipitation as well as selected monthly landslide distributions and their connection with weather anomalies. Landslide distributions are correlated with precipitation records of a synthetic precipitation series as a representative for the study area. The annual landslide distribution shows an overall increasing number of events with alternating periods of low and high landslide activity. Correlation with the annual precipitation predominantly reveals a more frequent occurrence of landslides in humid years. The monthly landslide distribution between 1901 and 2016 shows a first accumulation of events in winter months (January–March: 31%) and a second one in summer months (June–August: 32%). In general, this monthly landslide distribution follows the annual course of precipitation. Particular monthly landslide distributions are apparent for periods of increased landslide activity which coincide with exceptional long-term winter and summer precipitation trends. In these periods the monthly distributions widely follow the annual precipitation courses. Overall, the results show that the precipitation is basically suitable for an explanation for the occurrence of landslide events. Whereas the annual precipitation is only partially meaningful for the annual landslide activity, the influence of exceptional seasonal precipitation is reflected in the monthly landslide distributions. The results provide a promising basis for more detailed analyses of the relationship between landslides and the precipitation in the study area.