Modeling of sediment generation from forest roads employing SEDMODL and its calibration for Hyrcanian forests in northern Iran

Forest roads network is one of the main sources of sediment generation in the forest watersheds. It is difficult to estimate the sediment rate using direct methods, because of more time consuming and costs. Therefore, it is vital to use erosion and sediment models that require less time and cost. To start with, the study area (northern Iran) was selected by homogeneous units based on different digital layers such as soil texture, geology, precipitation, and topography in geographic information system and supported by extensive field surveys. Afterward, the sediment trapping wooden dams were constructed on the output culverts in homogeneous units. Next, the trapped sediments were measured in 45 wooden dams and compared with the values of estimated sediments using SEDMODL 2.0. After that, thirty wooden dam samples were used for modeling/calibration aims and the remaining 15 wooden dams were used for model validation. As a result, comparing the observed sediments with the estimated sediments by SEDMODL, it has been revealed that the mean estimated sediment rate by SEDMODL was about 8% less than the actual observation values by the direct method. Moreover, the results showed that average trapping coefficient of the sediment was about 0.25 (sediments traps on the road edges). Finally, validation results for 15 wooden dams were used to investigate the accuracy of the model. Accordingly, the results exposed an increase in model efficiency after calibration for the given forest area. To enclose, the overall results showed that SEDMODL model can contribute as a tool for a quick, accurate, and acceptable generation of estimations accommodating sediment yields.