An assessment of land degradation and its effects on geomorphology using LADA model: a case study of Ilam Province, west of Iran

Land degradation is an environmental issue and it is described as the decrease of land stability. The available definitions of land degradation, methods to measure it, and the pertinent measures are diverse and controversial. Desertification and land degradation in Iran are serious issues and need assessment and survey to realize a stable land management in different regions of the country. The land degradation assessment in dryland (LADA) project has been initiated by the FAO over the past few years. The project is an attempt to introduce a set of standard methods and instructions to assess land degradation processes, the factors, and the effects with participation of local communities and users. The main objective of the present study is to assess land degradation and the effects on development and geomorphological forms in the west of Iran (Ilam Province) using LADA model. To do this, MODIS spectroradiometer (MOD13Q1 (250 m) NDVI) was used to examine trends of vegetation changes. In addition, LANDSET 7 & 8 data were used to assess change trend of surface water resources and salinity (BI, SI). The data provided by piezometer stations were used to examine change trend of groundwater resources and soil sample and measure EC and PH of the soil from 2000 to 2017. The results showed that land degradation has been expanding from the west to the east all over the region under study in terms of NDVI plant coverage during the time period under study. As illustrated by the images, vegetation degradation was more severe in the west and southwest of the region under study in sub-basins West/East Abbas Plane, Mosian, and Chenaneh, in the west of the region and sub-basins Abdanan, Dehloran, Mehran, and Salehabad in 2000, 2005, 2010, 2015, and 2017. Vegetation in these areas is low at all times. The change slope, change slope significance, 8-year predication of change trend, and vegetation change difference indices supported the findings. While changes in the surface water resources have been increasing with a slight slope due to construction of dams in the region, these changes have had no effect on preventing and controlling land degradation in the region, since these resources have been affected by the land degradation on the far west strip. Moreover, in terms of the groundwater resources level, out of 76 piezometric well, 49 well with negative water level changes and 27 well with positive water level changes were identified. This means that all the well with declining water level was on the west strip (sub-basins Mosian, Abdanan, Dehloran, and Mehran). However, ascending wells are mostly concentrated in in the sub-basins east and west of Dasht Abbas—i.e., the southwest of the region under study. The ascending water levels in these wells can be explained by expansion of Karkhe water grid and less demand for the ground water in the region. Salinity and brightness indices assessments and soil lab results showed the lands with maximum salinity index and 100% soil degradation were at the west strip of the region or the west and south of Ilam Province (Mehran, Mosian, Abdanan, West/East Dasht Abbas, and Moulab). Eventually, land degradation and its effects on formation of geomorphological forms in the region were examined. The results revealed that land degradation in the west and southwest strip of the region, where the degradation is critical, has created specific geomorphological forms such as gully erosion.