3.2 The assessment of the P factor
The P factor, anti-erosive factor, represents the relationship between farming practices and slope. It’s a simplified expression of the effects of various agricultural practices aimed at minimizing the impact of rainfall, reducing runoff, and hence limiting soil loss (Wischmeier and Smith, 1978). P factor values in agricultural areas decrease as the slope decreases, while on steep terrain, these values increase.
In other words, when the slope is gentle, farming practices can better mitigate the impact of rainfall, thus reducing the risk of erosion. Conversely, on steep terrain, the slope itself can exacerbate the effects of erosion, leading to higher P factor values. The idea is to consider the interaction between agricultural practices and topography to assess the effectiveness of soil conservation techniques in erosion prevention.
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3.1.1 The RUSLE/SIG approach
Early erosion modeling models were empirical, such as the Universal Soil Loss Equation (USLE) developed by Wischmeier and Smith in 1978 (Wischmeier & Smith, 1978), and its revised version, the Revised Universal Soil Loss Equation (RUSLE). RUSLE, a predictive model for soil erosion, considers factors such as precipitation intensity, terrain slope, vegetation cover, and soil type. The integration of GIS (Geographic Information Systems) into RUSLE modeling enables the visualization of areas most susceptible to soil erosion and aids in identifying appropriate soil conservation practices to mitigate erosion risks. The steps to implement the RUSLE/GIS approach involve data collection and preparation, RUSLE modeling, and results assessment to determine the most suitable soil conservation practices (Renard et al., 1997). GIS is crucial in this approach as it facilitates the visualization of results and the identification of high-risk areas for soil erosion The Revised Universal Soil Loss Equation (RUSLE) is a comprehensive model that estimates soil erosion, considering factors such as the Rainfall Factor (R), Soil Erodibility Factor (K), Topographic Factor (LS), Vegetative Cover Factor (C), and Support Practice Factor (P). Each of these factors plays a crucial role in assessing the potential for soil erosion (Renard et al., 1997; Wischmeier & Smith, 1978). In summary, the RUSLE/GIS approach is a four-step process that integrates empirical models with GIS for effective soil erosion modeling and conservation planning. The cited references provide foundational insights into the development of these models and their application in soil conservation.