Rainfall interception by vegetation is an essential part of the hydrological water cycle. Part of the intercepted rainfall evaporates to the atmosphere, and throughfall and stemflow contribute to surface runoff, affect soil erosion and infiltration processes and control soil moisture and runoff connectivity patterns. Depending on land cover, the interception can exceed 40% of the rainfall amount. One of the possible effects of changing climate is a change in rainfall characteristics, including amount, intensity, and frequency. The impact of these changes on the rainfall interception, raindrop structure, velocity and erosive power is, however, still not well understood.

The new international scientific collaboration with partners from the University of Ljubljana, and the Slovenian Forestry Institute investigates the impact of meteorological and land cover characteristics on changes in raindrop structure, interception, and erosive power of rainfall. The main research aims are to investigate and compare mechanisms of rainfall interception and throughfall microstructure below different vegetation types at the experimental urban and forest plots in Slovenia and experimental agricultural basin (HOAL) in Austria.

High frequency (1-minute) measurements of rainfall characteristics above and below different vegetation types in urban, forest and agricultural environments will be carried out to evaluate the impact of changed raindrops structure on erosive power of rain and sediment transport in the streams in different seasons representing pheno phase and snowmelt impacts. These measurements will be analysed and modelled by up to date data mining techniques. The differences in raindrop structure and rainfall erosivity will be attributed to different meteorological, vegetation and seasonal factors.

Cooperation between experts from the Slovenian Forestry Institute, University Ljubljana and TU Wien enables to look on rainfall interception from a holistic perspective, i.e. by considering simultaneously several dependent variables (such as rainfall interception, runoff generation and rainfall erosivity) in an interdisciplinary context. Advanced measurements of real rainfall structure by disdrometer devices allow understanding better the relations between meteorological conditions, rainfall characteristics, runoff generation patterns and erosion processes at the plot and small catchment scale.

The project's original contribution is to understand the link between rainfall interception, soil erosion, and sediment transport processes and to develop new interdisciplinary collaboration between hydrology, forestry, agriculture, and engineering. The practical outcome of the project is to develop strategies for planning and implementing green infrastructure as part of the measures to reduce the impacts of soil erosion.