INTRODUCTIONSoil degradation, defined as the change in physical, chemical, and biological properties of the soil resulting in a diminished capacity of the ecosystem to provide goods and services for its beneficiaries (FAO, 2020), leads to the degradation of ecosystem services (Cerretelli et al., 2018). Soil degradation includes erosion, salinization, soil loss following erosion after deforestation or overgrazing, compaction, crusting caused by cattle trampling, and waterlogging with impaired water movement (Scanes, 2018).The soil properties play a crucial role in determining soil health and degradation. Different soil properties directly influence the physical, chemical, and biological characteristics of the soil, which in turn affect its ability to support plant growth, retain water, and nutrient cycle, and resist degradation. Thus, various soil properties, such as soil texture, structure, water holding capacity, organic matter content, soil reaction, and electrical conductivity contribute to the vulnerability of soil to degradation processes (Rabot et al., 2018; Lorenz et al., 2019; Barcelos et al., 2022; Zhang et al., 2022)A watershed is a topographic unit containing aquatic and terrestrial ecosystems, with various land-use types such as forest, pasture, and agriculture. Watersheds play a major role in the important requirements in human life, such as water supply, and agricultural and animal production. Besides, watersheds are also important for other creatures that benefit from ecosystem services. Godrahav watershed consists of different land-use types. For example, forestry, animal husbandry, and agricultural production are carried out in the watershed. The problem of soil degradation may disrupt the ecosystem services provided by the watershed.Researchers reported the main reasons for the soil degradation in the watershed as degraded forest, water erosion, and shifting cultivation (Amundson et al., 2015; Hattori et al., 2019; Baul et al., 2023; Mo et al., 2023;). Different methods and models are used to evaluate soil degradation. Until now, the loss of organic matter, decrease in carbon and nitrogen content, change in grain size distribution, salting, acidification, compaction, and erosion have been evaluated as degradation separately. For example, plant nutrient deficiency was considered as chemical degradation, and soil compaction as physical degradation.Multivariate models are used based on the approach that more than one type of degradation can be seen in an area. A global evaluation of soil degradation requires sampling and evaluation methodology, and a degradation metric meets the needs and interests of multiple different groups (Hatfield et al., 2017).Multicriteria decision analysis (MCDA) is an umbrella term to describe a collection of formal approaches which seek to take explicit account of multiple criteria in helping individuals or groups explore decisions that matter (Belton and Stewart, 2002). MCDA provides a compatible methodological framework for deliberative valuation, which is considered helpful in addressing plural value dimensions related to common goods such as ecosystem services.This study was carried out in a watershed to determine the soil properties and their spatial variability and distribution. It was also aimed to calculate the soil degradation index with different weighting methods and determine the spatial variability and spatial distribution of the soil degradation index. Besides, determining the effect of topography and land use differences on soil degradation index is another purpose of the present study. A model was developed using the GIS-based MCDA to determine the spatial distribution of the soil degradation index. Created GIS-MCDA models are based on established soil properties that affect soil productivity. The model was used to classify watersheds of low, medium and high soil degradation index. The hypothesis was that some topographic factors such as altitude, aspects and slope, and land use correlate to the soil degradation index.
