There are also man-made hydraulic jumps created by devices like weirs or sluice gates. The bubbler pool could be drained by opening its sluice gates. The reservoir covered and provided water to scour the channel below the sluice. Processing of placer ore material consists of gravity-dependent methods of separation, such as sluice boxes. The sluice which powered the waterwheel and sluice keeper's cottage still exist. The sluice gate tower and watchtower were dismantled in 1935. Shuiguanmen was located near Zhengyangmen's eastern sluice gate. The second way to bypass the Little Sluice is to drive up Toyota Rock. These sluice gates are called "aboiteaux". A sluice, called for in the act, was designed to help scour out The Haven. Each sluice gate is closed once a month for testing. It was designed to be used in areas with less water than a sluice box. Lumber to build new homes, sluice boxes, etc. The trail then continues toward the Big Sluice. It is long with 24 arches, and also serves as a sluice gate.