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Creek. The July 28, 1997 discharge was 8,250 cfs while the FEMA 500-year discharge was 3,325 cfs, an exceedance factor of2.48. This is the water that ponded behind the Burlington Northern railroad embankment, swept four rail cars off the tracks, and overtopped the tracks, resulting in flooding of the trailer park to the east. Downstream of College Avenue, the discharge decreased to about 5000 cfs. This was because of the storage behind the railroad embankment. Even with the storage, at Mathews Street, the estimated flow exceeded the previously-established 500-year level by a factor of2.98, The 500- year flood at the railroad trestle was supposed to be 2,920 cfs, but the estimated flow was 5,860 cfs, a factor of2.01. Some of the tributary urban flows shown on Table I show even greater exceedance factors. Table 2 The storm greatly exceeded the design capacity for stormwater facilities in the City, By 8:30 p.m" when more than 3 inches of rain had fallen, the detention ponds began overtopping. The additional six inches of rain that fell in the next hour and a half did not have anywhere to go. To further complicate matters, trailers jammed up against the College Avenue bridge blocking the bridge opening, In addition, many arterial streets were overtopped and damaged. On the Colorado State University campus, Ayres Associates had prepared drainage plans and was able to compare simulation models with the actual event. As shown on Figure 6, water generally flows from west to east across campus, The main confluence is near the intersection of Elizabeth and Shields Streets, and several other streets contribute as well. During a minor event, most water is captured by the storm sewer system and does not affect the campus; but in larger events, water ponds and begins to overflow. Figure 9 The drainage area that contributes to the campus begins' at the foothills. Canals normally capture small runoff, but large events on the order of25-year larger begin to overtop these canals. Two channels from the foothills, the West Plum Channel and the Clearview Channel, bring water into the canals and in large events tend to spill water from the lower canal (Larimer #2 Canal), and the overflow concentrates near City Park and West Elizabeth Street. Water then enters the campus near the Moby Gym and, after overtopping the Arthur ditch, it flows into the Library parking lot and north into the Lagoon, In very high water, additional drainage also comes from the South part of campus. Then, the Lagoon area starts to overtop, water flows into the Engineering lot, which ponds and then releases overflows into the Oval, Water ponds in the Oval, floods the Heating Plant, and eventually flows through a pedestrian underpass at the railroad track, Water then flows past the gym, and ultimately overtops College Avenue and goes down Locust Street to the east. In 1996, Ayres identified potential damage areas on the campus and estimated water surface elevations for frequencies up through the 100-year event. This was done using a modified version of the Stormwater Management Model (SWMM). The study identified 6