Slope Length and Steepness factor (LS-factor)
|The Universal Soil Loss Equation (USLE) model is the most frequently used model for soil erosion risk estimation. Among the six input layers, the combined slope length and slope angle (LS-factor) has the greatest influence on soil loss at the European scale. The S-factor measures the effect of slope steepness, and the L-factor defines the impact of slope length. The combined LS-factor describes the effect of topography on soil erosion. The European Soil Data Centre (ESDAC) developed a new pan-European high-resolution soil erosion assessment to achieve a better understanding of the spatial and temporal patterns of soil erosion in Europe. The LS-calculation was performed using the original equation proposed by Desmet and Govers (1996) and implemented using the System for Automated Geoscientific Analyses (SAGA), which incorporates a multiple flow algorithm and contributes to a precise estimation of flow accumulation. The LS-factor dataset was calculated using a high-resolution (25 m) Digital Elevation Model (DEM) for the whole European Union, resulting in an improved delineation of areas at risk of soil erosion as compared to lower-resolution datasets. This combined approach of using GIS software tools with high-resolution DEMs has been successfully applied in regional assessments in the past, and is now being applied for first time at the European scale.|
LS-factor in Europe
The methodology presented in this paper for estimating the LS-factor has the following features:(a) uses a high-resolution DEM at 25 m, (b) applies the Desmet and Govers (1996) algorithm , and
(c) limits the estimation of LS to a maximum slope angle of 50% (26.6 degrees). We used a new high-resolution (25 m) DEM of the European Union (EU-DEM) to calculate the LS-factor. The EU-DEM provides pan-European elevation data at 1 arc-second, and is a hybrid product based mainly on Shuttle Radar Topography Mission (SRTM) and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global Digital Elevation Model (GDEM). The EU-DEM was developed through the Copernicus program, and its statistical validation documents a relatively satisfactory overall vertical accuracy of 2.9 m root mean square error. This resolution of the EU-DEM is the best available at the European scale.
The application of the methodology resulted in the first topographic mapping of the LS-factor at 25-m resolution for the European Union (Figure 1). The greatest LS-factor values are observed in mountain areas such as the Alps (Slovenia, Austria, Italy and France), the Pyrenees (Spain), the Apennines (Italy), the Carpathian mountains (Romania) and the Pindos mountain range (Greece). The mean LS-factor value for the whole European Union is 1.63, with a range of 0 to 99. LS-factor values greater than 25 were found in only 0.1% of the whole European Union, mainly located in Austria, Greece, Italy and Slovenia.
Due to its high (25 m) resolution, the European LS-factor dataset is more than 50GB in size. LS-factor datasets per country can be downloaded after compiling the request form. The LS-factor dataset is in Raster format. The public user can download 2 different resolution datasets :
- 100m resolution for the Whole Europe
- 25m resolution per country.
A complete description of the methodology and the application in Europe is described in the paper:
Panagos, P., Borrelli, P., Meusburger, K. (2015) A New European Slope Length and Steepness Factor (LS-Factor) for Modeling Soil Erosion by Water. Geosciences, 5: 117-126.
Fig. 1: Slope Length and Steepness factor (LS-factor)
||Title: LS-factor (Slope Length and Steepness factor) for the EU|
Resource Type: Datasets, Soil Threats Data
Registration requested: Request Form
Publisher: European Commission, Joint Research Centre