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- 11 - -12 - held the waters from doing any damage in the area below there. The angry waters extended clear down to Grand Junction. Man-made features constructed within the flood plain or immediately adjacent to the channel bed obstruct flood flows and create flooding dangers greater than what would have occurred naturally. Man-made obstructions in the flood plain and channel bed consist of irrigation diversion structures, bridges, culverts, buildings, and pipe crossings. Most of these obstructions are present in the Breckenridge area. All the channel crossings, which consist of bridges, culverts and pipelines, if not properly engineered will collect debris and create backwater conditions which cause water levels to rise to the extent that more land is inundated by flood waters. Also, erosion problems will arise when the natural flow of the river is obstructed and narrowly confined. The strength capability of the bridges and culverts can sometimes be excecded and the crossing destroyed, creating further debris and headwater flowing in the channel and flood plain. ~he bridge on the Whatley road caved in to a degree, but fast effort on the part of the high- way crew saved it, and kept one more route of communication open. Only a constant vigil on the part of the many con- cientious men made the saving of this great street possible. The town water crew, town marshal, councilmen, county commissioners, and sheriff's department put in many long hard hours, serving above and beyond the call of duty, but with a love for their "high country" and its welfare, upper- most in their hearts. Flooding within the town of Breckenridge was a function primarily of backwater from culverts and bridges that were plugged with debris. Consequently, flooding waS most extensive around each of the major crossings and localized in the stretches between the crossings. The runoff approachod the 100-year recurrence storm. Other obstructions in the flood plain, such as commer- cial and residential building~ also create additional flood hazards. Structures in the flood plain restrict flood flows and reduce the carrying capacity of the natural flood plain. Cons~quently, backwater effects occur Which result in in- creased velocities of flow at and belOW release points. On July 23 of the same year the Blue River left its banks for a second time. The flood was attributed to a storm of high intensity centered over d O<"L<lll triiJutdry "'wOVe th", LOWH. Because of the time of year, rainfall runoff was the predom- inant cause of flooding. Prior to the storm the flow in the Blue River was 400 cfs and was generally decreasing. GOOSE PASTURE TARN F~CTORS AFFECTING FLOODING A major feature in the Breckenridge area that contrib- utes to a reduction in flood damage is the Goose Pasture Tarn. The reservoir is located immediately upstream of the town of Breckenridge and has a drainage area of approximately 43.5 square miles. The storage capacity of the reservoir is nearly 1000 acre-feet wi.th a spillway design capacity of 5,000 cfs. Through the process of storing and gradually releasing flood waters from the tributaries, the res,-,rvoir plays an important role in reducing the peak discharge of rainfall-runoff in the Blue River prior to its entering the town of Breckenridge. The value of the reservoir for Flooding is a natural function of a river and its tribu- taries. In the process of flooding, vegetation, debris and other natural obstructions imppde flood flows and cause baCKwater conditions that increase flood heights. The debris is washed downstream anc COllected on bridges and culverts creating a danuning effect. As flood flows increase the <lcc'll'lulated. debris may break loose and a wall of ",.ater anu debris s\lrgcs do'"-'nstream until another obstruction ~s en- countered. C\> .'J:"4ru~",Cur~":I.~'A'",,,E,>;",,,,,~,Iri.' C\> ,8('!'."j~ICM~I:I""1'.':'l'.["'i"e",:r:c, --- ----- _.- --- __ _n____________ ------