Dr. Victor Miguel Ponce

4711. BACKWATER Documentation

BACKWATER will calculate an M1 water-surface profile for a natural channel using the standard-step method (Chow, V. T. 1959. Open-channel Hydraulics, McGraw-Hill). The program will take only SI units. Use distances in meters, and discharge in cubic meters per second. The program will prompt you to enter discharge Q, downstream stage yd (water-surface elevation), and number of cross sections n. Next, the program will prompt you to enter data for n cross sections, ordered from upstream to downstream. For each cross section, three (3) records are required: Cross-section identifier SECTID (an alphanumeric string of 20 characters or less) (1 value). Distance DIST to next downstream cross-section, left-bank Manning n XNL, in-bank Manning n XNC, right-bank Manning n XNR, x-coordinate limiting left-bank channel and center channel XBL, x-coordinate limiting center channel and right-bank channel XBR, and number of x-y coordinates to specify cross-section NP (integer) (7 values). NP pairs of y-x coordinates for the cross section (2*n values). Enter a dummy value (say, 0.) for DIST in the b record of the last (downstream) cross section. The program will report a table of corresponding data containing the following: Sequential integer, varying from 1 to n; cross-section identifier; velocity (m/s); hydraulic radius (m), water-surface slope (m/m), and water-surface elevation (stage) (m). Caution: Please make sure that your input data makes sense from a hydraulic standpoint. The downstream stage yd should be greater than or equal to the normal depth for the specified cross section and relevant hydraulic data.