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<br />001538 <br /> <br />32.7 <br /> <br />WATER INFORMATION MANAGEMENT SYSTEM HANDBOOK <br /> <br />Note: This relation will be developed for as many elevation zones as the <br />user chooses. Alternatively, if the data are not stratified by elevation <br />zones, the user may develop a relationship of the form Q8 . f(DA,E), where <br />E = e levat ion. <br /> <br />Step 3 - Calculate drainage area, area-weighted mean elevation, or other <br />appropriate watershed characteristics for ungaged points of quan- <br />tification. For ungaged points of quantification develop the same data as was <br />regressed against the log-Pearson 1.5 years return interval flow in Step 2. <br /> <br />Step 4 - Calculate bankfull discharge (Q8) for ungaged points of <br />quantification using the relation developed in Step 2 and the data in Step 3. <br /> <br />Step 5 - Proceed to Section 32.8, Common Step 1. <br /> <br />32.7 - Method E. Use this method in essentially non-erodible/bedrock stream <br />channels. It differs from other methods in that the maintenance flows needed <br />are those which provide only for the transport of tributary and/or introduced <br />sediment. Further, since the width of non-erodible/bedrock channels does not <br />adjust to frequent discharges, bankfull width cannot be used as an indicator <br />of "bankfull" or other discharges. <br /> <br />The maintenance flow requirement for non-erodible/bedrock stream channels does <br />not include rise-recession, baseflow or vegetation encroachment prevention <br />flows because bank erosion and vegetation encroachment potentials are <br />considered to be negligible. Consequently, only the magnitude and duration of <br />"bankfull" discharge are considered as needed for channel maintenance. <br /> <br />Step 1 - Secure the following data for the representative and all suitable <br />gage stations: <br />a. Channel width vs. discharge or water stage vs. discharge relations. <br />b. Drainage area of watershed above gage. <br />c. Area-weighted mean elevation of watershed above gage. <br />d. Other watershed characteristics if appropriate. <br /> <br />Secure the following data for the representative gage station: <br />e. Duration table of daily values summary. <br />f. Mean annual discharge. <br />g. Daily mean hydrograph data for the period of record. <br /> <br />Step 2 - Using either field measurements of discharge or hydraulic geometry <br />relations (or cross-sectional area data) with the stage-discharge curve from <br />the representative gage station, determine the discharge at the bankfull <br />(QB) stage for the representative gage station. <br />