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<br />I <br />I I <br />I <br /> <br />I <br /> <br />content of the snow varied from about 4 to 6 inches. The estimated peak <br /> <br /> <br />discharge of 16,400 c.f.s. at the Rock Rapids gage was equivalent to <br /> <br /> <br />about a 10-year event. The gage height at Rock Rapids for this flood <br /> <br /> <br />was recorded at 9.56 feet. <br /> <br />I <br />I <br />I <br /> <br />I <br /> <br />FLOOD OF 1969 <br />On 8 April 1969, the greatest flood on the Rock River recorded to <br />date was caused by snowmelt. The snow depth in the basin was from 15 to <br />20 inches with a water content of 4 to 8 inches. The peak discharge at <br />Rock Rapids was estimated to be 29,000 c.f.s., which is equivalent to <br />about a SO-year event. The gage height at Rock Rapids was recorded at <br />10.23 feet. <br /> <br />I <br />I <br />I <br />I <br /> <br />On 29 June 1969, a discharge of 18,900 c.f.s. was estimated at the <br /> <br /> <br />Rock Rapids gaging station, with a gage height recorded at 9.42 feet. <br /> <br /> <br />This flood was greater than a 10-year event; however, no other information <br /> <br /> <br />was available. <br /> <br />I <br /> <br />I <br /> <br />FLOOD OF 1993 <br />Two major flood events at Rock Rapids took place on 8 Kay and 11 July <br />1993. The two events were approximately equal in magnitude, with a gage <br />height of 12.53 feet recorded during the May flood. Based on gage <br />readings, the 1993 floods crested about 2.3 feet higher than the previous <br />flood of record in 1969. The peak stages were measured by City officials <br />at a former USGS gaging site near the confluence of Moon Creek with the <br />Rock River. A specific return period was not estimated or assigned to <br />either of the two 1993 floods. However, it would be reasonable to <br />assume that the floods may have been close to a 100-year event based on <br />information gathered about the floods and by analyzing peak river stages <br />and recorded high water marks. Approximately 8 inches of rain fell in <br />12 hours upstream from Rock Rapids during the July event. In addition, <br />flash flooding on 17 July 1993 on Moon Creek flooded areas on the north <br />side of town more severely than the two previous Rock tlver floods of <br />that year. <br /> <br />I <br /> <br />I <br />I <br /> <br />I <br />I <br />I <br /> <br />14 <br />