Abstract
In 2011 the Marshal Office of Malopolska Voivodeship decided to evaluate the vulnerability of soils to water erosion for the entire region. The quantitative and qualitative assessment of the erosion risk for the soils of the Malopolska region was done based on the USLE approach. The special work-flow of geoinformation technologies was used to fulfil this goal. A high-resolution soil map, together with rainfall data, a detailed digital elevation model and statistical information about areas sown with particular crops created the input information for erosion modelling in GIS environment. The satellite remote sensing technology and the object-based image analysis (OBIA) approach gave valuable support to this study. RapidEye satellite images were used to obtain the essential up-to-date data about land use and vegetation cover for the entire region (15,000 km2). The application of OBIA also led to defining the direction of field cultivation and the mapping of contour tillage areas. As a result, the spatially differentiated values of erosion control practice factor were used. Both, the potential and the actual soil erosion risk were assessed quantificatively and qualitatively. The results of the erosion assessment in the Malopolska Voivodeship reveal the fact that a majority of its agricultural lands is characterized by moderate or low erosion risk levels. However, high-resolution erosion risk maps show its substantial spatial diversity. According to our study, average or higher actual erosion intensity levels occur for 10.6 % of agricultural land, i.e. 3.6 % of the entire voivodeship area. In 20 % of the municipalities there is a very urgent demand for erosion control. In the next 23 % an urgent erosion control is needed. Our study showed that even a slight improvement of P-factor estimation may have an influence on modeling results. In our case, despite a marginal change of erosion assessment figures on a regional scale, the influence on the final prioritization of areas (municipalities) according to erosion control needs is visible. The study shows that, high-resolution satellite imagery and OBIA may be efficiently used for P-factor mapping and thus contribute to a refined soil erosion risk assessment.
Highlights
Introduction and backgroundSoil erosion, defined as the detachment of soil particles and their transport by wind or water, is a natural process driven by physical factors
The main objectives of this paper are as follows: (i) to give an overview of the USLE-based highresolution regional scale erosion risk modeling approach, which has been adopted for the prioritization of administrative units according to erosion control urgency; (ii) to assess the usefulness of object-based image analysis (OBIA)
The data used for the survey can be divided into two main categories according to their source: (i) data taken from existing spatial databases and (ii) data derived from remotely sensed imagery
Summary
Soil erosion, defined as the detachment of soil particles and their transport by wind or water, is a natural process driven by physical factors. The energy necessary for soil particle detachment and its transport is provided by wind or water (rain or surface runoff). Soil particles detached and redeposited during this process fill the macropores. It results in a decrease of infiltration and an increase of surface runoff and, in turn, the erosion rate down to the slope. Even if the raindrops fall into a layer of surface water and do not detach the soil particles directly, they increase soil erosion, increasing the transport capacity of water as an effect of the increased turbulence (WARD and ELLIOT 1995)
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