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downstream of the radial gate. The high velocity under the gate keeps this area clear The operation of the radial gate and the sluicing capacity are not affected by the downstream tailwater. Figure 50 shows the dunes that formed upstream of the Union Avenue dam. The deposits indicated by this test would probably take several years to occur, unless there is a relatively large flood in 1 year. Sediment deposits affect flow patterns in the pool. However, flow patterns are acceptable for boating before or after deposition occurs. Before the sand deposits, the flow gradually turns toward the second chute on the left bank. A back eddy forms downstream from the dam which will carry boaters or sediment back towards the toe of the upstream dam. After the pool partially fills, the back eddy is eliminated and the flow forms a channel turning gradually from boatchute ] to boatchute 2. Floodflows Discharges up to the COE 100-year flood of 16,400 ft'/s were observed in the model. Figure 5] shows the model operating at the 100-year floodflow. Table 3 lists the water surface profiles measured at flows ranging from 500 to 16,400 ft'/s. Model data indicate that the water level is contained within the streambanks up to the 100-year flow. Profiles through boatchute 1 are plotted on figure 52. Profiles were measured down the centerline of boatchute 1. The wave was highest along the centerline due to the V-pattern downstream of the boatchute. However, the height of the wave did not cause a major problem for the model boats navigating the boatchute. It was found that the height of the wave could be reduced by spreading the wave across the width of the boatchute; however, this was not considered to be desirable since the boats turned sideways when the wave was spread out. The undular shape of the wave downstream of the boatchute was maintained throughout the entire flow range. Undesirable reverse rollers, which may trap boaters, do not form at any flow. Flow over the main crest. - At flows greater than 200 ft'ls, the water started overtopping the main spillway crest. The exact amount of flow will depend on the amount of sluicing and flow into the Englewood intake. For flows between 200 and 1,000 ft'ls, boats tended to "hang up" on the main crest and downstream wedge (fig. 18) due to shallow water. When the water was deep enough for boats to clear the crest, they passed on through into the tailwater pool area. The configuration with the wedge and downstream riprap prevented reverse rollers from forming downstream from the main crest. The 3-foot riprap on the downstream face of the dam experienced only minor movement during the 100-year flood event; therefore, 3 feet of riprap should be adequate to protect the embankment. The area between the boatchute and the sluice wall experienced major erosion during the 100-year flood; therefore, some type of stabilization is recommended for this area. During the model tests, the size of the rockfill embankment was reduced by shortening the 1 to 10 slope to 130 feet long, before dropping off at a 3 to 1 slope to the bottom of the stilling basin (fig. 53). This change reduced the amount of material required by 1,500 yd'. The additional material was not necessary since the area below the tailwater level to the left of boatchute 1 will be a deposition area. A large eddy formed in the pool which caused a large sand deposit where the rockftll embankment was originally planned. The sand bar accumulation continued to almost the end of the original stilling basin wall. When a 100-year flood was observed after the sand bar 12