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<br />4.3 <br /> <br />Damages from the 1969 flood were not -as E!xtensive as the flood of 1914 and <br />were confined to the western side of town. Sediment deposits ranged in depth <br />from 2 to 6 feet in these two events. Boulders in excess of 20 tons were <br />transported by the 1914 event. II map showing the approximate limits of each <br />flood is shown as Figure 4.1. Historic photographs of damage from the 1914 flood <br />are presented as Figures 4.2a through 4,2d. The approximate location and <br />direction of the views shown in the historic photographs are delineated on the <br />map. <br /> <br />4.3.2 Existing Flood-Protection HeaSU1"eS <br />No engi neered fl ood-protecti on structures have been constructed along <br />Cornet Creek other than bridges and riprap bank protection. A berm constructed <br />of rocks and soil, approximately 8 to 10 feet in height and 100 feet in length <br />exists at the mouth of the Cornet Creek canyon. Its purpose is to contain flows <br />from the mouth of the canyon and direct them away from the eastern and central <br />portions of town. According to available historic photographs and discussion <br />with personnel from the Publ ic \~orks Department of Tell uride, the berm has <br />existed since the early 1900s. The berm was washed out during the 1914 mud flow <br />event but was replaced. Occasionally, debr-is deposited in the creek at -the <br />mouth of the canyon has been re~lOved and added to the berm by Pub 1 i c Works <br />personnel. <br /> <br />4.4 HvdroloQic Analysis <br />4.4.1 General <br />Historically, high-intensity thunderstonns occurring in mid-to-late summer <br />cause mud floods and mud flows along Cornet Creek. Water flooding can occur <br />during spring snowmelt. The most severe nooding, however, is associated with <br />thunderstorms. These storms are the result of warm, moist air movement from the <br />Pacific being driven over the Rocky Mountains. Floods along Cornet Creek <br />originating in this manner are characterized by a rapid rise in discharge and <br />short duration. <br />Mud flow hydrographs of speci fi c return peri ods for Cornet Creek are <br />required to delineate flood-hazard areas in the town of Telluride. Assigning <br />mud flood and mud flow events a given return period, how,ever, is difficult due <br />to the complex i nterrel at i onshi ps between ra i nfa 11, sed i ment sources, and <br />watershed/channel characteri st ics. The procedure outl i ned in thi s report <br />