Laserfiche WebLink
<br />chance of occurrence in an average year. These depths and <br />velocities are determined through a statistical analysis <br />that considers both the probability distribution of flood <br />discharges at the fan apex and the probability that the <br />flood channel(s) will inundate particular locations down the <br />fan. for example, if a given contour on the fan is 100 feet <br />wide and the la-year flood discharge flows in a channel that <br />is 10 feet wide. the probability that a given location on <br />this contour will be flooded by the la-year discharge event <br />is approximately IX. The IX probability depth and velocity <br />at this contour are the depth and velocity in the 10 foot <br />wide channel carrying a la-year flood discharge. Depending <br />upon the width of the fan contour and the width of the <br />channel the 1X probability depth and velocity will <br />correspond to different flood discharges at different fan <br />locations. <br /> <br />In.deriving a technique <br />velocities, certain key <br />hydraulics were made. <br /> <br />for calculating these depths and <br />assumptions regarding fan flood <br /> <br />1) At the time of passage of the peak discharge of <br />a flood event, the flow is confined in a single <br />channel from the fan apex to the toe. <br /> <br />2 ) <br /> <br />Flows are at critical <br />(Froude number = 1). <br /> <br />depth and velocity <br /> <br />3) Below the apex. the flood channel occurs at <br />random locations at any point on the fan. <br /> <br />4) The flow erodes its own channel. stabilizing <br />the shape of the channel when the decrease in <br />channel depth per unit increase in channel <br />width approximates 0.005. <br /> <br />53 <br />