[Task 4] Partially Raised Gates for Low-Flow Management March 13~14

Task 4, partially raised gates for low-flow management to develop a curve depicting the results to aid the City in the event the pool elevation needed to be controlled manually, and to observe sediment accumulation.

Gates #1 and 2 were fully opened and gate #17 was 1 ft down on 13-Mar (figure 1). This configuration stayed 24 hours.

On 14-Mar, water depth increased up to 4.2 ft, so the gates #3 and 4 were opened (figure 2). Purpose of this configuration is to develop a relationship between the partial gate opening and water depth change.

However, river inflow discharge is changing continuously, so the relationship should be considered for gate operation reference only.

Water depth at each surveying section was taken from kayak. Figure 2 shows the section XC3 (upstream of the intakes). Comprehensive water depth map of the diversion dam upstream will be posted soon.

Figure 1 Figure 2 section XC3

Also, sediment depositions were deposited along the gate (gates # 9–24 were detected with paddle probing). Especially, at the gates #22-24, huge sand packs were found as shown in figure 3. Gates #22-23 were fully opened during the task 3 (6-7, March), and all gates except gates #23 and 24 were fully opened on last Monday (12-Mar) for cross section surveying. After only 5 days, sand bars are relocated, but direction, speed, and volume are not predictable. These huge sand packs can also make gate operation problems. The sand packs suppose to be flushing out using gate opening on 15-Mar. Sediment flushing test (certain sand pack volume flushing speed) will be worth to try.

Figure 3 Figure 4