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<br />In almost any direction. Thi~: can occur because thE~ flo~~s tend to build <br /> <br />their own channels as levee m,aterial 1.8 deposited at the lateral boundaries <br /> <br />of the flows. This process is discussed m detail in the Appendix. <br /> <br />Furthermore, <br /> <br />a previous flow surge can steIp wit:hin an existing channel and deflect a <br /> <br />succeeding flow to a new dil:ecticln. As a result, the potential hazard <br /> <br />from boulder-laden flows several feet high may be spread randomly over <br /> <br />an entire debris fan surface, regal'dless of manls attempts to channelize <br /> <br />the flows. This important point is discussed further in Chapter V. <br /> <br />Debris-flow velocity is an import..nt factor when defense against the <br /> <br />flows is considered because it enables rough calculations of the dynamic <br /> <br />pressures and discharges. There is very littl,= information about debris-flow <br /> <br />velocities reported in the literature, but we have exceptionally good data <br /> <br />on the Glenwood Springs flo~is obt:ained from eyewitnesses to the events <br /> <br />and from calculations. <br /> <br />Mr. Julian Vogt, who observed the muddy, boulder-laden flow near his <br /> <br />house on Bennett Avenue, estimated the flow velocity to be approximately <br /> <br />5 mph (8.0 km/hr) or slightly more (7 ft/sec, 2.1 m/sed. His house is <br />located on the unconfined debris fan approximately 500 ft (150 m) below <br /> <br />the mouth of Gulch A. The fan gradient at this location is roughly 70. <br /> <br />Flow depth in this area, as inferred from mud marks on t re e sand bu i ld i ng s <br /> <br />(Figure 6) was approximately 5 ft 0.5 m). Mr.. Charles Stoddard also observed <br /> <br />flows near his house, located on Palmer Avenue, approximately 200 ft (60 <br /> <br />m) below the mouth of Gulch B. He estimated flow velocity of roughly 10 <br /> <br />.. 22 - <br />