Laserfiche WebLink
<br />001583 <br /> <br />32.3 <br /> <br />WATER INFORMATION MANAGEMENT SYSTEM HANDBOOK <br /> <br />to adjust its boundaries in response to changes in frequent flows. As a <br />result, it is usually impractical to measure channel characteristics at the <br />gage station in the literal sense. Therefore, make channel measurements <br />above or below the gaging site. <br /> <br />32.3 - Method A. Use Method A where stream cross-sectional area and water <br />surface slope can be measured at gaged sites and all points of <br />quantification. <br /> <br />Step 1 - Secure the following data from the representative gage station and <br />all suitable gage stations. Some of these data will require collection in <br />the field if unavailable from station records. <br /> <br />a. Hydraulic geometry and related discharge. <br />b. Stage-discharge relation. <br /> <br />, <br />c. Channel cross sectional area at bankfull stage (and baseflow stage <br />for the representative station). <br /> <br />d. Water surface slope at bankfull stage. <br /> <br />e. Wetted perimeter, hydraulic radius, and roughness (if Manning's <br />equation is used to estimate discharge). <br /> <br />f. Field-measured bankful discharge, if feasible. <br /> <br />Secure for the representative gage station the following: <br /> <br />a. Duration table of daily values summary for the period of record. <br />b. Mean annual discharge. <br />c. Daily mean hydrograph data for period of record. <br /> <br />Step 2 - Determine bankfull discharge and baseflow for the representative <br />gage station. Usin~ either field measurements of discharge or hydraulic <br />geometry relations (or cross-sectional area data) with the stage-discharge <br />curve from the representative gage station, determine the discharge at the <br />bankfull (QB) stage. Using depth ratios, stage, or cross sectional area <br />determine discharge at the baseflow (QLl) stage. (Note: Baseflow stage <br />is the water surface elevation associated with the discharge that just <br />fills the thalweg or inner berm channel.) <br /> <br />~ _ Collect data at all suitable gage stations. <br />banKfull discharge as described in step 2. <br /> <br />Calculate or measure <br /> <br />Step 4 - Develop general relationship. <br />and all suitable gage stations and using <br />technique, develop the relationship: <br /> <br />From the data of the representative <br />an appropriate statistical <br /> <br />QB = kA(\sY <br /> <br />III No. 3 <br />8/28/87 <br />