Understanding Sediment Yield Processes in a Hyrcanian Forest Watershed

Sediment yield mirrors the resultants of interaction between many different watershed components and therefore can be studied for better understanding the governing situations on a watershed system. Despite of the general belief on existence of persistent conditions in forest ecosystems, the determinant factors on sediment yield in such watersheds are numerous and complicated as well. Till date, many researches have tried to correlate sediment yield and flow discharge from a watershed but the comprehensive studies on formulating the dynamic conditions are very rare. As a consequence, the proper management of the watershed cannot be affectively achieved. In the present study, it has been tried to understand the controlling factors of suspended sediment yield in a forest watershed in Iran comprises ca. 50,000 ha as a representative of Hyrcanian forest. The study was conducted through daily suspended sediment sampling for a period of some 1.5 years. The results, besides approving the inapplicability of sediment rating curve in estimation of suspended sediment concentration, proved the high changeability of sediment yield in the study period. Results also showed a complex suspended sediment concentration and flow discharge relationship of the study watershed reflecting the effect of subtle variation in different anthropogenic, climatic, sediment availability and consequently sediment supply.