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Corps dispatched crews to install staff gages upstream from Hamburg to monitor river rises. Additional crews were also dispatched for helicopter and ground tours to try and identify the location of the flood crests coming down the West Nishnabotna River and the East Nishnabotna River. The helicopter over-flight was conducted from about 3:30 pm to 5:30 pm on June 16th. The helicopter survey report was phoned back to the water control office where the information was used to dispatch the USGS flow measurement team to the confluence of the East and West Nishnabotna Rivers. Additional crews were also dispatched to Hamburg to . monitor the levee and assist locals with flood fight activities. Staff gages were also installed at Highway 42 near Riverton (about 6 miles upstream from Hamburg), 2 miles downstream from Riverton (about 2 miles upstream from the Hamburg gage), at HO" Street in Hamburg and at the Highway 275 bridge in Hamburg, These staff gages, in addition to the USGS gage located 2 miles upstream from Hamburg, provided valuable information in monitoring the flood event. At Highway 42, it was reported that water overtopped the road sometime in the early morning of June 16th and rose to about 4 feet over the road by early afternoon when the staff gage was installed. It rose an additional 1.4 feet in 2 hours by 3:30 pm. At the gage 2 miles downstream, the stages were already rising at about the time the staff gage was installed at 6:00 pm and rose another 3 feet by midnight. About 9:00 pm on June 16th the USGS finished making a discharge measurement along Highway 42. They measured a total combined flow of 90,000 cfs from both the East Nishnabotna River and West Nishnabotna River. Because of the 90,000 cfs measurement, the Corps advised the local emergency authorities of the potential for the levee to overtop at Hamburg and recommended evacuation of the low areas of town. The Hamburg levee was designed to pass 47,000 cfs with 2 feet of freeboard. It was estimated that the levee could pass about 60,000 cfs with no freeboard. The NWS was also contacted and informed of the 90,000 cfs discharge measurement. At 10:40 pm the NWS issued a revised flood warning. By 10:45 pm on Tuesday night, the locals began evacuating the City of Hamburg. Shortly before midnight, the stages at the Hamburg gage began rising rapidly. The L-575 tie back levee began overtopping about 2:00 am on June 17'h, Water reached near the top of the Hamburg levee in the early morning hours of June 17'h, but did not overtop the levee. The Nishnabotna River at Hamburg crested at a stage of 33.18 feet at 7:30 am on Wednesday morning June 17'h. This stage exceeded the previous record stage of 30.56 feet that occurred in 1993 by 2.62 feet. The USGS measured a discharge of 61 ,200 cfs at 10:00 am on the morning of June 17'h. 19