Simulating with a combination of RUSLE GIS and sediment delivery ratio for soil restoration.

Erosion by water is the main cause of land degradation. Landscapes degraded by erosion need to be restored in many respects, and particularly in terms of ecosystem services. From an economic and management perspective, care is needed to select priority areas and determine the means to be applied to restore them. Globally, the model most commonly used to produce scenarios for the prevention of soil losses is the Revised Universal Soil Loss Equation (RUSLE). This study of the subbasin of the Sulakyurt Dam Basin in Turkey aims (1) to identify the distribution of soil losses over time and by location, and (2) to grade the priority areas for the prevention of soil losses by means of a simulation. The average potential soil losses in the area under study are estimated at 42.35 t ha-1 year-1, and the average actual losses at 39.49 t ha-1 year-1. According to the simulation, 27.61% of the study area (2782 ha) is of the highest priority for soil restoration. In our study, forests have the highest soil losses, which is contrary to the natural protection that forests provide against erosion. The high rates are due to the slope, the forest area is very steep. So it is the slope factor that outweighs the vegetation cover factor. Of the forest areas, 41.74% (1766 ha) falls within the areas of highest priority. The study serves as a guide for landscape planning and the determination of erosion risk in restoration efforts, and for identifying the methods to be adopted during the restoration work to reduce the loss of soil.

Analysis of methods to determine the sediment retained by check dams and to estimate erosion rates in badlands.

Check dams are useful structures at a catchment scale to determine erosion rates using the sediment retained in their wedges. Several studies employ different complex, accurate methods to estimate them. We likewise evaluate which catchment variables affect these erosion rate values. Our study aims to compare five frequently used methods (two prismatic and three topographic) to evaluate how they estimate total sediment yield (TSY) at two locations in Central Spain. For this purpose, we determine the sediment trapped in each area by 25 check dams built during the twentieth century. We also evaluate the catchment variables influencing TSY rates. Results show differences between methods in TSY determinations at the 90 % confidence level, although there are no differences between locations or the location-method iteration. We found that the natural logarithm of the drainage area was the factor that best explained TSY, presenting a negative trend (partial correlation coefficient, 0.83). Vegetation cover factor had no influence in estimating TSY for the two locations. We conclude that the determination of TSY rates depends on the chosen method and four related variables: check dam length, check dam height, wedge length and check dam drainage area. Furthermore, it is important to analyse and select the best method to estimate erosion rates based on the sediment retained by check dams depending on the characteristics of the study area (channel and sediment wedge shape), method accuracy and field effort. A more accurate estimation of erosion rates will allow researchers to determine the role of check dams in controlling sediment in each specific restoration project.