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<br />1957 <br />1975 <br />1983 <br />1984 <br /> <br />3,300 cfs <br />3,360 cfs <br />3,460 ds <br />3,920 cfs <br /> <br />June 29 <br />July 4 <br />June 24 <br />May 22 <br /> <br />FLOODING CHARACTERISTICS <br /> <br />During a flood, the velocity of flow in the channel of the <br /> <br /> <br />river averages 6-10 feet per second throughout the study reach. <br /> <br /> <br />Floodwaters in the overbank may flow as slowly as 1 foot per <br /> <br /> <br />second. Given these floodwater flow rates a number of phenomena <br /> <br /> <br />will occur. Water flowing at a rate of 7.-8 feet per second or <br /> <br /> <br />greater will cause severe erosion of s1:reambanks and lands and is <br /> <br /> <br />capable of transporting rocks and large trees. Water flowing at <br /> <br /> <br />about 2 feet per second or less will deposit sand, silt and other <br /> <br /> <br />floodborne debris. <br /> <br />The floodplain has a number of natural and man"'made <br /> <br /> <br />obstructions to streamflow including trees, brush, gravels, <br /> <br /> <br />rocks, and various other structures. Without stabilization <br /> <br /> <br />structures or natural streambank armament, the river will migrate <br /> <br /> <br />across the floodplain during periods of flood, as was experienced <br /> <br /> <br />in many locations during the 1983 and 1984 floods. <br /> <br />-4... <br />