Laserfiche WebLink
<br />DISCUSSION OF RESULTS <br /> <br />Although equation 10 provides a good means of estimating channel <br /> <br />roughness, there are several explanations for the error associated with <br /> <br />the equation. Equation 10 predicts the average roughness of the reach <br /> <br />of a stream rather than of an individual subreach. The flow conditions <br /> <br />in steep streams are extremely turbulent and add to the measurement <br /> <br />error an unknown component which is not present in more tranquil streams. <br /> <br />Although the channel reaches selected were primarily contracting, <br /> <br />there were some cases where expansion did occur and could not be avoided. <br /> <br />were due to channel expansion. <br /> <br />These losses could pose serious problems <br />/ <br /> <br /> <br />Expanding reaches also affected the stream data collected by Barnes <br /> <br />(1967) and Limerinos (1970). Although a detailed investigation was not <br /> <br />made, it was noted that in some cases the energy loss in terms of Manning's <br /> <br />n (since the contraction and expansion coefficients were held constant <br /> <br />at 0.0 and 0.5, respec.tively) was as much as 61 percent higher in expanding <br /> <br />reaches than in contracting reaches. There were no measurable differences <br /> <br />in bed material throughout each reach, indicating that the energy losses <br /> <br />in hydraulic studies of streams because these studies might encompass <br /> <br />many expanding reaches. <br /> <br />31 <br />