Seasonal variation of the erosion rate using direct measurement

Soil erosion and its consequences are the major obstacles for development of country. Understanding the erosion dynamics and recognizing sensitive times and places to erosion within the catchment are very important for erosion control. This study attempts to investigate the dynamic process of soil erosion in terms of temporal (seasonal) and spatial (geological rock units) changes, via direct measurement of erosion in Vartavan catchment. For this purpose, after mapping the precise lithological units, sediment trappers were placed on the slopes of each unit and the sediments of trappers were collected and after drying were weighted at the end of each season. The study confirmed the dynamic nature of erosion in this watershed and results showed that erosion has great temporal and spatial variations. Seasonal variation of erosion revealed that autumn has the maximum rate of erosion (71%) and then decreases respectively during the spring (19%) and winter (10%), until reaches the minimum rate at summer. The mean weight of accumulated sediment is also reduced respectively in units of plagioclase tuff (178.2 gr), black shale (34.4 gr), red mudstone (29.9 gr), andesine (21.7 gr), tuff (16.7 gr), sandstone (14.9 gr), red sandstone (9.8 gr), shale limestone (9.5 gr) and eventually orbitolina limestone (6.5 gr). These results can be applied for watershed management programs and the amount of erosion can be reduced using temporal (preservation of vegetation and control of plowing at critical seasons) or spatial (focus on erosion control measures in sensitive places) management.