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<br />6.1 <br /> <br />VI. SUMMARY AND CONCLUSIONS <br />6.1 ,Sul1lllary <br />During the 1914 flood event flows followed a path on the eastern side of <br />the Cornet Creek alluvial fan. Remnants of this channel can still be seen near <br />the fan apex. After 1914, the Cornet Creek cha,nnel is believed to ha,ve been <br />relocated to its present position on the western side of the fan, A berm, <br />approximately 100 feet in length and 6 to 8 feet in height, has also been <br />constructed at the fan apex to confine flows within the existing creek channel, <br />If the berm is overtopped or fails during a flood event, flows can be expected <br />to proceed towards the east side of the fan due tn the influence of the historic <br />channel. <br />The results of this study indicate that the berm which exists at the fan <br />apex will be overtopped by the 100-year return period water flood event. The <br />berm does not meet FEMA standards for a 1 evee, The berm wi 11 not prevent <br />widespread flood inundation on the fan. The extent of flooding for water flood, <br />without,berm conditions was found to be approximately the same as for the with- <br />berm condition. For the with-berm condition, wa,tE!r flood depths of approx"imately <br />1 foot can be expected over most of the fan. For the without-berm case, depths <br />of flooding on the eastern half of the fan were found to slightly increase: <br />For mud flow events, the influence of the berm .on the conditions of <br />flooding on the Cornet Creek alluvial fan were seen to be much more significant. <br />A lthough the berm was overtopped, for the ~Iith, berm cond it i on the extent of <br />inundation due to mud flow was restricted mainly to the western half .of the fan. <br />Without the berm, the eastern side of the fan is expected to experience much <br />greater flood inundation. Blockage of the channel or a potential failure of the <br />berm, both possible during a 100-event, can be expected to have much greater <br />impact on the eastern side of the Cornet Creek alluvial fan. For either the <br />with- or without-berm condition the maximum depths of inundation during the 100- <br />year mud flow event on the Cornet Creek alluvial fan can be expected to exceed <br />6 feet in localized areas. <br /> <br />6.2 Conclusions <br />This study demonstrates the importance of cantrall ing flood discharges from <br />Cornet Creek near the fan apex. Flood inundation has been shown to be a function <br />of channel capacity, berm freeboard, potentia"1 for channel obstruction, and <br />obstructions to flow paths caused by structurE~s, particularly near t.he fan apex. <br />