In order to genteel the stream water from sedimentation by logging road construction, riparian area along stream channel must be carefully managed. Buffer strips, however, have not been implemented in the forest land outside those watersheds of major reseviors in Taiwan. As the forest polity is changed from timber production to water resources protection, a standard of buffer strip width is needed foe forest planning in the acne future. Based on the distance of sediment casted downstage daring the road construction at Liu-Kuei experimental forest in southern Taiwan, a buffer strip width (in meter) calculate by the equation as 10+0.03×(SLOPE, in degree)^2 is proposed in similar forest land.