Evaluation of the impact of rainfall interception on soil erosion

Description:

​Three research organizations, namely Faculty of Civil and Geodetic Engineering at the University of Ljubljana (UL FGG), Slovenian Forestry Institute (GI) and Technical University of Vienna (TUW) will jointly contribute to the proposed research project with their expertise in the field of rainfall interception and rainfall erosivity. The main aim of the project is the improvement of knowledge about rainfall interception by different vegetation and its impact on the rainfall erosivity based on high-frequency measurements at the already established experimental plots. Knowledge about this issue will be of paramount importance in the future, as due to climate change even more frequent and intense rainfall events with high erosive power can be expected. Investigation of rainfall partitioning is important both in natural environments as well as in urban areas. Urban trees reduce surface runoff, influence the evaporation and infiltration of water and may be due to the climate change more frequently used in the future as a part of green infrastructure. In natural environments rainfall interception and therewith rainfall erosivity is one of the most important parameters of the soil erosion with significant impact on the agricultural production and ecological conditions of the streams. Knowledge about sediment transport processes is relevant for controlling soil loss from agricultural land. Due to different types of vegetation, their unique characteristics and seasonality there are still a lot of open scientific questions.

In order to achieve the main objectives of the project we will conduct extensive field measurements at three different experimental plots, namely two in an urban area of Ljubljana and one in an agricultural catchment in Austria. All three experimental plots will enable us to enhance the current research work and connect knowledge and experience of all three partners. At two locations in Ljubljana trees play important green infrastructure role. Currently, UL FGG is performing measurements in the urban park, where rainfall partitioning under individual trees of two different tree species is measured. On the other hand, GI is performing measurements in the urban mixed forest. In the frame of the project at both locations optical disdrometers will be used to measure drop size distribution (DSD) above and below tree canopies. Due to the fact that rainfall partitioning is influenced by numerous variables, we will simultaneously measure also several meteorological and vegetation parameters during different seasons. No measurements of rainfall interception have been performed so far at the catchment in Lower Austria. However, a substantial number of raingauges and a weather station are already part of the monitoring setup in the catchment. Furthermore, also intensive sediment monitoring is already in progress. In the scope of the project DSD measurements using optical disdrometers positioned above and below selected crops will be conducted in combination with classical measurements of rainfall partitioning.

Based on the collected data and extensive analyses we will try to answer several open questions, such as what is the influence of different meteorological variables on rainfall and throughfall DSD in different climates, what is the influence of rainfall interception process on throughfall DSD below different types of vegetation (i.e. deciduous trees,  coniferous trees, crops) in different seasons, what is the impact of the rainfall interception process on the erosive power of raindrops. Cooperation of experts of all three partners and comparison of the results of the analysis of high frequency measurements under different natural conditions related to climate, vegetation and soil is certainly an innovative research approach. 

Main goals:

The main aims of the project are:

• Identifying the influence of several meteorological characteristics (e.g. rainfall amount, intensity and duration, wind speed and direction, air temperature, air humidity) on rainfall and throughfall DSD in different climates. Simultaneous high frequency measurements of meteorological variables and rainfall DSD above and below vegetation will be conducted at the experimental plots/catchments in Slovenia and Austria.
• Identifying the influence of rainfall interception by different types of vegetation, namely several types of trees and crops on throughfall DSD in different seasons (i.e. phenophases). High frequency measurements of rainfall DSD above and below two types of individual trees, namely birch (Betula pendula Roth.) and black pine (Pinus nigra Arnold), above and below urban mixed forest as well as above and below selected crops (e.g. maize, winter wheat, winter barley) will be conducted at the experimental plots/catchments in Slovenia and Austria.

Identifying the impact of rainfall interception process on the erosive power of raindrops (i.e. rainfall erosivity) as one of the most important factors of soil erosion. Comparison of the influence of rainfall interception on throughfall DSD and therewith on soil erosion between crops (experimental catchment in Lower Austria) and trees (two experimental plots in Ljubljana, Slovenia) will be conducted.

Project work packages:

Work on the research project will be divided into next four work packages (WPs):

WP1: Project management and coordination

The objective of this work package is to ensure that the project goals will be fulfilled. In order to achieve this immediately after the start of the project, we will determine the detailed timetable of the planned activities, installation of measuring equipment, organization of the work (e.g. monitoring, data analyses, modeling), partner meetings, reports, dissemination activities, etc.

WP2: Measurements and database

The focus of WP2 will be on measurements and a project database establishment that will be used in the next WPs. The current equipment that all three project partners are using at their three experimental plots/catchments, namely experimental plot in urban park in Ljubljana, experimental plot in urban forest in Ljubljana and experimental catchment at Lower Austria, will be upgraded to the scope of this research project. The selection of these three experimental plots/catchments will enable us to enhance the current research work and connect knowledge and experience that all three project partners have.

WP3: Modelling and analysis

The focus of WP3 will be on computer simulations and analysis of measurements gained in the scope of the project (WP2) using advanced modelling methods, comparative hydrology, and connection of knowledge and interdisciplinary experiences of the project members from the past research and projects.

WP4: Synthesis and dissemination

Measurements, analyses of the results, developed methods and models, and other conclusions that will be obtained as a result of this project will be presented in at least 4 international peer-reviewed scientific and professional journals in the fields of hydrology, forestry or agronomy with a high impact factor. Additionally, the results of the project will be published also in at least 4 national scientific and professional publications as well as at least 4 international (e.g., EGU, IUFRO) and national conferences. Moreover, project updates will also be distributed through different social media channels, where the focus will be to address public.