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84 TABLE 9.2 Example of SRICOS-EFA Program output file data can be either in the metric system or U.S. customary sys- Woodrow Wilson Bridge Flow Velocity Chart tem; the output also can be in either system. The User's Man- (from 1960 to 1998) ual for SRICOS-EFA is presented in Appendix D of the 3 research team's final report, which is available from NCHRP. 2.5 Velocity (m/sec) 2 9.6 OUTPUT OF THE SRICOS-EFA PROGRAM 1.5 Once the program finishes all of the computations success- 1 fully, the output file is created automatically. The output file includes the following columns: time, flow velocity, water 0.5 depth, shear stress, maximum scour depth (pier, contraction, or 0 total), and instantaneous scour depth (pier, contraction, or 19601963196619681971197419771980198319851988199119941997 total). The first few days of a typical output file of the program Year are shown in Table 9.2. For this example, the critical shear stress was 4 N/m2; as can be seen, no scour occurred until the Scour Depth Vs Time 7000 velocity was high enough to overcome the critical shear stress on day 11. The format of the output file is a text file. This file 6000 Scour Depth (mm) can be used to plot a number of figures (Figure 9.10). The most 5000 commonly plotted curves are water velocity versus time, water 4000 depth versus time, shear stress versus time, and scour depth ver- 3000 sus time. The scour depth versus time curve indicates whether 2000 the final scour depth Zfinal (scour depth at the end of the hydro- 1000 graph) is close to the maximum scour depth for the biggest flood in the hydrograph Zmax or not. Typically, in sand the 0 1960 1965 1970 1975 1980 1985 1990 1995 answer is yes, but in low erodibility clays the difference is sig- Time (year) nificant enough to warrant the analysis in the first place. Kwak et al. (2001) showed the results of a parametric analysis indi- Figure 9.10. Example of plots generated from SRICOS- cating the most important parameters in the prediction process. EFA output.