국내 하천 형상을 반영한 SWAT 모형 내 하천폭 및 홍수터폭 산정 회귀식 도출

Derivation of Channel and Floodplain Width Regression Reflecting Korean Channel Shapes in SWAT Model

Abstract

In this study, the channel and floodplain widths are indirectly measured for three different watersheds using satellite images to reflect the shape of Korean channels in the Soil and Water Assessment Tool (SWAT) model. For measuring the channel and floodplain widths, multiple satellite images were referred to ensure the widest width of certain points. In the single channel, the widths at the multiple points were measured. Based on the measured data, the regression equations were derived to estimate the channel and floodplain widths according to watershed areas. Applying these developed equations, this study evaluated the effect of the change of channel and floodplain widths on the SWAT simulation by comparing to the measured streamflow data. The developed equations estimated larger channel width and smaller floodplain compared with those calculated in the current SWAT model. As shown in the results, there was no considerable changes in the predicted streamflow using the current and developed equations. However, the flow velocity and channel depth calculated from the developed equations were smaller than those of the current equations. The differences were caused by the effect of different channel geometries used for calculating the hydraulic characteristics. The channel geometries also affected the water quality simulation in channels because the hydraulic characteristics calculated by the channel geometries are directly related to the water quality simulation. Therefore, application of the river cross-sectional regression equation reflecting the domestic stream shape is necessary for accurate water quantity / quality and water ecosystem simulation using hydrological model.

Fig. 1 Locations of study areas (three watersheds for channel width measurements (a)~(c) and one watershed for swat model application (d))

Fig. 2 Landuse Maps for study areas

Fig. 3 Landuse, Soil and Watershed Maps for Ju-cheon watershed

Fig. 4 Measurement method of channel and floodplain widths using satellite image

Fig. 5 Comparison of current and newly developed regression equations for estimating (a) channel and (b) floodplain widths

Fig. 6 Comparison of (a) bankfull width and (b) floodplain width estimated by the current and newly developed regression equations for Jucheon watershed

Fig. 7 Comparison of (a) water depth and (b) flow velocity estimated by current and newly developed regression equations for Ju-cheon watershed

Fig. 8 Comparison of suspended solid estimated by current and newly developed regression equations for Ju-cheon watershed

Table 1 Analysis landuse at study areas

Table 2 Analysis slope at study areas