Impacts of extreme wind speeds and other factors on tree fall alongside railway lines

High wind speeds are a major cause for tree fall. However, the impact of wind on trees can depend on other co-occurring or antecedent meteorological conditions. Tree fall can also have an impact on surrounding infrastructure like the railway system. Here, it may damage railway infrastructure and lead to train disruptions. The intensity and frequency of windstorms and other meteorological factors is expected to change in the course of a changing climate. Thus, their impacts on trees and tree damage might change as well. To understand these changes an examination of impact-relevant weather factors and sequences is needed.
We obtained a dataset for tree and branch fall events alongside German railway lines from the Deutsche Bahn for the years 2017 to 2021. We use logistic regression to model tree fall probabilities and to identify relevant current and antecedent weather factors, their combinations and their impact on tree fall risk during winter. We use meteorological predictors derived from the ERA5 reanalysis and RADOLAN radar data.
High wind speed is identified as the strongest risk increasing factor. However, high daily precipitation and high soil water volume during the tree fall event as well as an antecedent year with high precipitation also increase tree fall risk. A small decreasing effect was found for warm and wet soil conditions in the three preceding months. We found no or only minor effects for daily mean air temperature, storm duration and wind direction.
In further steps these factors and their combinations will be assessed in terms of their effect on occurrence probabilities of tree fall events under recent and future climate conditions based on regional climate simulations.