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<br />- 12 - <br /> <br />! <br />, <br />i <br /> <br />Man-made features constructed within the flood plain or <br />immediately adjacent to the channel bed obstruct flood flows <br />and create flooding dangers greater than what would have <br />occurred naturally. Man-made obstructions in the flood pla~n <br />and channel bed consist of irrigation diversion structures, <br />bridges, culverts, buildings, and pipe crossings. Most of <br />these obstructions are present in the Breckenridge area. All <br />the channel crossings, which consist of bridges, culverts and <br />pipelines, if not properly engineered will collect debris and <br />create backwater conditions which cause water levels to rise <br />to the extent that more land is inundated by flood waters. <br />Also, erosion problems will arise when the natural flow of <br />the river is obstructed and narrowly confined. The strength <br />capability of the bridges and culverts can sometimes be <br />exceeded and the crossing destroyed, creating further debris <br />and headwater flowing in the channel and flood plain. <br /> <br />, <br />, <br />i <br />! <br />, <br />I <br />.. <br />, <br /> <br />Other obstructions in the flood plain, such as commer- <br />cial and residential building~ also create additional flood <br />hazards. Structures in the flood plain restrict flood flows <br />and reduce the carrying capacity of the natural flood plain. <br />Consequently, backwater effects occur which result in in- <br />creased velocities of flow at and below release points. <br /> <br />GOOSE PASTURE TARN <br /> <br />A major feature in the Breckenridge area that contrib- <br />utes to a reduction in flood damage is the Goose Pasture Tarn. <br />The reservoir is located immediately upstream of the town of <br />Breckenridge and has a drainage area of approximately 43.5 <br />square miles. The storage capacity of the reservoir is <br />nearly 1000 acre-feet with a spillway design capacity of <br />5,000 cfs. Through the process of storing and gradually <br />releasing flood waters from the tributaries, the reservoir <br />plays an important role in reducing the peak discharge of <br />rainfall-runoff in the Blue River prior to its entering the <br />town of Breckenridge. The value of the reservoir for <br /> <br />~ Leonard Rice Consulting Water Engineers, Inc. <br />