The goal of this study was to evaluate sediment reduction effects of VFS(vegetative filter strip). This study simulated runoff and sediment load from different types of uplands using VFSMOD-W. The general upland characteristics of the Iksan study area was investigated to build reasonable scenarios of the simulation. The simulation scenarios were designed by various areas, shapes, and slopes of uplands. Grass mixture was selected as VFS vegetation and the size of VFS was fixed as 10% of uplands area. In this study VFSMOD-W program was calibrated based on filed monitoring data and applied on Saemangeum area.

Results obtained from this study are summarized as follows :

1. The results of statistical investigations of the general characteristics of Iksan upland showed that the common sizes of uplands were between 0.1ha and 0.2ha, and 86.2% of them accounted for less than 1.0ha and the dominant soil type was loam and mainly located 7~15% of slope areas. The hydrologic soil group features usually belong to Type B.

2. From the preliminary simulation, the calculated runoff and sediment loads were obtained 20.7∼1,030.6m3 and 568.4 ∼ 675,731.4kg for the range of 0.1∼1.0ha of uplands with 7% and 15% slopes. The reduction effects on runoff and sediment were obtained 5∼10% and 21.0∼47.7% respectively from VFS applications. The VFSMOD-W simulations showed that runoff tended to increase as upland area and amount of rainfall increased while sediment increased when slope, length and area of uplands and amount of rainfall increased. These results indicated that rainfall amount and upland size are the critical factors for the generation of runoff and sediment load.

3. Model calibration has been performed with the limited monitoring data taken from Iksan experimental field. Several important parameters were calibrated such as CN, K facotr, C factor, P factor, Sav, , Manning''s roughness coefficient. Calibration results showed reliable range with NSE = 0.833 for runoff and NSE = 0.794 form sediment.

4. Calibrated parameters applied for Saemangeum watershed based on the simulation scenarios. The runoff reduction efficiency was obtained 2.0~4.4%, while the sediment trap efficiency was calculated 19.7~42.7%.

5. These results showed that the possible range of sediment reduction effects when the VFS measurement applied for the given upland fields conditions. Further study needs to calibrate them with long term field experiments to get more reliable simulations.