This study was carried out to examinate drainage effect of the shallow horizontal culvert which can drain off excess water quickly in rainy wet season for produce forage crops stably in the paddy. The results of this study are as follows. In the measured data of soil moisture change for 38 hours after 37㎜ rainfall, the value of soil moisture tension in untreated control plot was 21.1kPa, while values of soil moisture tension for 3m, 5m, 7m culvert interval in treated control plot were 25.9kPa, 23.1kPa, 22.4kPa, respectively. Accordingly, soil moisture of treated control plot was shown more dried soil than that of untreated control plot. also, an average value of ground water level in untreated control plot was -4.3㎝, while average values of ground water level for 3m, 5m, 7m culvert interval in treated control plot was -31.1㎝, -27.8㎝ and -21.7㎝, respectively. It shows to go down 22.6㎝ comparing an average value of ground water level in treated control plot with that of ground water level in untreated control plot.