R-Factor in Switzerland

R-Factor

Rainfall erosivity, considering rainfall amount and intensity, is an important parameter for soil erosion risk assessment under future land use and climate change. Despite its importance, rainfall erosivity is usually implemented in models with a low spatial and temporal resolution.

Here, we present a study (done in 2012) which aims to assess the temporal- and spatial distribution of rainfall erosivity in form of the (Revised) Universal Soil Loss Equation R-factor for Switzerland. Time series of 22 yr for rainfall (10 min resolution) and temperature (1 h resolution) data were analysed for 71 automatic gauging stations distributed throughout Switzerland.

Notice: It is reccomended to take into account the updates of the study "Rainfall erosivity in Europe"

Computation of R-factor

RUSLE R-factor is the product of kinetic energy of a rainfall event and its maximum 30-min intensity (Brown and Foster, 1987). R-factor (rainfall erosivity) measured as MJmmha−1 h−1 yr−1, is the cumulative sum of a number of erosive events of a given time period (year). The criteria for the identification of an erosive event are given by Renard et al. (1997): 
(i) the cumulative rainfall of an event should be greater than 12.7mm, or 
(ii) the event has at least one peak that is greater than 6.35mm in 15 min and 
(iii) a rainfall-period of less than 1.27mm in 6 h is used to divide a longer storm period into two storms. 
In our code we modified the second criteria of Renard et al. (1997). A threshold of 8.47 mm/20 min instead of 6.35 mm/15 min was used in order to best fit to the time resolution of the precipitation data (10 min). The likelihood to observe an 8.47 mm/20 min event is slightly smaller than a 6.35 mm/15 min event.

Some stations may be elevated and a large proportion of the annual precipitation occurs as snowfall that the heated stations measure erroneously as rainfall. For this reason a temperature threshold, below which precipitation records are not considered when searching for rainfall events, was used. Here we applied a temperature threshold of 0 C (degrees) (Leek and Olsen, 2000).

The algorithm was implemented in C programming language. The proposed algorithm can be reused for other local/regional/national applications where rainfall data and temperature data are available with the same temporal resolution. The users can either run the algorithm as it is (EXECUTABLE file) or modify the C File and develop their executable. In the first case they have to follow STRICTLY the Instructions given. Download the Instructions guide.

Documentation about the code and the example data may be found in the referenced publication: Spatial and temporal variability of rainfall erosivity factor for Switzerland. An introductory presentation entitled Rainfall erosivity assessment for Switzerland is also available.

 

Example Application: Rainfall erosivity mapping for Switzerland

Title: Rainfall erosivity mapping for Switzerland
Description: This map provides a complete rainfall erosivity dataset for Switzerland based on 71 stations and 22 years of measurements. Regression-kriging was used to interpolate the rainfall erosivity values of single stations and to generate a map for Switzerland. 
Spatial coverage: Switzerland
Pixel size: 500m 
Projection: ETRS89 Lambert Azimuthal Equal Area 
Temporal coverage: 22 years (1989 - 2010)

Input data source: Measurements of 71 stations in Switzerland (22 years time)

Information: Panos Panagos, Katrin Meusburger, 
European Commission, Institute of Environment and Sustainability, Land Resources Management Unit AND Institute of Environmental Geosciences, University of Basel

References

A complete description of the methodology and the application in Switzerland is described in the papers: 

 


Data - Application (Code)

The Rainfall Erosivity data is in Raster format. The code for the calculation of Rainfall Erosivity is in C programming Language (An executable file is also included). To get access to the data and the code, please compile the  request form; instructions will then follow how to download the data and code.

 The existing executable application is proposed for 10-minutes precipitation data (and optionally 1-hour temperature data). The user may download the C-Programming language code and make the necessary modifications in case he has other time interval data. References to the source are always necessary!

Rainfall erosivity

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