An automated method for mapping physical soil and water conservation structures on cultivated land using GIS and remote sensing techniques

An efficient and reliable automated model that can map physical Soil and Water Conservation(SWC) structures on cultivated land was developed using very high spatial resolution imagery obtained from Google Earth and Arc GIS?ERDAS IMAGINE?and SDC Morphology Toolbox for MATLAB and statistical techniques. The model was developed using the following procedures:(1) a high-pass spatial filter algorithm was applied to detect linear features,(2) morphological processing was used to remove unwanted linear features,(3) the raster format was vectorized,(4) the vectorized linear features were split per hectare(ha) and each line was then classified according to its compass directionand(5) the sum of all vector lengths per class of direction per ha was calculated. Finallythe direction class with the greatest length was selected from each ha to predict the physical SWC structures. The model was calibrated and validated on the Ethiopian Highlands. The model correctly mapped 80% of the existing structures. The developed model was then tested at different sites with different topography. The results show that the developed model is feasible for automated mapping of physical SWC structures. Thereforethe model is useful for predicting and mapping physical SWC structures areas across diverse areas.

Deposition of eroded soil on terraced croplands in Minchet catchment,Ethiopian Highlands

In the Ethiopian Highlands,soil and water conservation practices are of utmost importance to conserve eroded soil and combat soil loss.This study provides detailed results on on-site sediment deposition and net soil loss in terraced croplands in a catchment in the sub-humid Ethiopian Highlands.Sediment deposition was measured on horse bean and maize fields during the crop growing seasons of 2014 and 2015.Measurements took place on observation plots on terraced cropland with varying spacing between terraces and varying slope gradients.Net soil loss,in this case the amount leaving the terraced cropland,was calculated by modelling the Universal Soil Loss Equation(USLE)for the whole observation field and subtracting the measured sediment deposition.The study result showed about 8–11 t ha^(−1) sediment was deposited in the deposition zone of the terraced cropland,with greater sediment deposition on terraces with narrow spacing and steeper slope gradients.Sediment deposition was highest in July and August,and relatively low in September.Annual soil loss ranged from 32 to 37 t ha^(−1) in the terraced cropland of the study area.From the total soil loss in the crop growing season,about 54–74%sediment was deposited on the deposition zone of terraced crop fields.Implementation of soil and water conservation with narrow spacing,especially on the steep slopes of the sub-humid Ethiopian Highlands or other similar area,are thus highly recommended as they enable conservation of the eroded soil in the cropland.