Handbook for Predicting Stream Meander Migration and Supporting Software (2004) / Chapter Skim
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7.1 INTRODUCTION This chapter defines the steps necessary to conduct a detailed meander migration analysis. The first method (Section 7.2)
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31 analysis. The opposite case may also occur, in which the final bend is a double-headed bend (Figure 7.4-H, -I, -M, -N, and -O)
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32 and 1966. The vector arrow at each bend shows the direction and magnitude of movement of the bend centroid between 1937 and 1966.
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33 Figure 7.6. Depiction of the bends from the 1937 and 1966 outer banklines as defined by best-fit circles.
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In Figure 7.9, the banklines predicted for 1998 by extrapolation of trends of change between 1937 and 1966 are superimposed on an aerial photograph taken in 1998. Two of the registration points used for this comparison are different because two of the original registration points from the previous aerial photos are no longer present on the 1998 aerial photo.
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35 alous rate. Because of problems inherent in using a long-term average rate of change, it is recommended that the most recent rate, the rate of change for the previous period (Period B in this case)
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as revetment, bridges, and levees that can have a significant influence on meander migration. The amount of migration of the bend centroid for Period A is DA, and for Period B it is DB.
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37 the group of registration points and banklines associated with one aerial photo has been superimposed onto the second aerial photo, the group can be correctly registered on that photo by resizing and rotating the group using the "Format Picture> Size" and "Format Picture>Rotate" tools. Right clicking on the picture accesses these tools.
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38 Figure 7.15. "Reach Data" dialog box of the Data Logger.
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39 The second script prompts the user for a file name in which the Virtual Table (VTab) for this sub-reach is to be stored (see Figure 7.17)
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40 • Upstream channel width (U-U) , • Bend apex channel width (A-A)
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41 • Orientation of the centerline of the bend, • Three channel width measurements, • Wavelength of the bend, and • Amplitude of the bend. Figure 7.25 illustrates the format in which the data are stored.
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42 Figure 7.25. Some of the data fields for Bend 1 and Year 1.
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43 Figure 7.29. Centroid, radius of curvature, and orientation of the predicted bend.
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44 migrating at less than the specified rate and 100 minus "x" percentage were migrating faster than the specified rate. These figures show that the C sites migrate faster than the A, B1, and B2 sites.
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45 Figure 7.31. Cumulative percentage of extension in channel widths per year.
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46 channel locations (outer bank only) are shown.
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