The total river basin areas of Macao gully is 13.1km2

the clear watersupply areas in upstream

the middle stream fault destructive belt areasand the down stream loess slide areas occupies 26%

32% and 42% of totalbasin area respectively. It is a viscous debris flow gully which bursts fre-quently

the solid substances of debris flow mainly come from middle anddown stream. The sediment load carried to Beiyu river occupies about onequarter of Beiyu river

so at the mouth of the river it threatens Wuducounty town. Although the landslides of the down stream of this gullyare connected in a large sheet

the mean free face hight of side in thegully wall is only 1.1m

the highest is no more than 4.5 m

and the axisof the slideis more or less vertical with the gully trough. It is suitablefor taking the measure to construct dam holding buck slides

for thisreason 13 dams were designed for main gullies

testing in two years forflood and debris flow has demonstrated that seven of the dams built madegood resulss.