Daily Sediment Estimation Using Dynamic Modeling in Kasilian Watershed

Soil erosion, transportation of eroded material and sedimentation cause many problems in the
hydrologic cycle of watersheds. Study of different stages of erosion and the recognition of control
methods is very important in planning and managerial activities . Extended studies have been
conducted in qualitative and quantitative evaluation of soil erosion, transportation and sedimentation.
Dynamic models known as time variant or memory models are those related to time and therefore,
time parameter plays an important role in system output. Dynamic models can be developed using
daily precipitation, water and sediment discharge collected during a specific period.
In the present study, the Kasillian watershed with an area of 6878ha located in forest region of
northern Iran, having considerable precipitation, discharge and sediment data, was selected. Initially,
the available precipitation, water and sediment discharge data for the period from 1970 to 1998 were
collected, refined and analyzed. Then, appropriate models were extracted using the concept of
dynamic modeling and subsequently the pertinent models were recognized based on the coefficient
of determination and estimation error criteria. The results indicated that the monthly classification of
the data led to achievement of better outputs as compared with those obtained from either no
classification or seasonally made groups. It was also found out that the daily sediment was not
affected by the precipitation, sediment and water discharge occurred respectively before ten, nine
and ten days. In other words the data belong to events previous to days before the mentioned time
could not affect the output of the models. It was also implied that the daily discharge highly affects
sediment concentration during the same day. The coefficient of determination and error percentage
of estimation in all the suggested models were respectively higher and less than 0.80 and 40% which
may verify the application of such models in daily sediment estimation in the study area.