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<br /> Human Stability in a High Flood Hazard Zone
<br /> TABLE 2. Data Summary ror 0.6 Percent Slope.
<br /> Flow Flow Hydraulic Ht. X Wt.
<br /> _""". VelDeity Depth Racnu. Produc~ Weillh~
<br />Subject Type rp. mi. ft em ft em Number (1nchea,lba)
<br />11 C 4.86 1.48 2.88 87.78 1.67 60.90 14.02 10,767
<br /> T 4.46 1.36 2.86 87.17 1.67 60.90 14.02 10,767
<br /> G 4.07 1.24 3.13 96.40 1.76 63.64 12.74 10,767
<br /> S 2.07 0.82 3,72 113.39 1.93 68.83 10.24 10,767
<br />.2 C 6.04 1.54 2.76 83.82 1.63 49.88 13.87 8,466
<br />'3 C 4.69 1.40 2.76 83.82 1.63 49.88 12.54 6,400
<br /> T 4.10 1.26 2.73 83.21 1.62 49.38 11.20 6,400
<br />.4 T 6.46 1.66 2,60 76.20 1.54 46.94 13.63 13,230
<br /> G 4.18 1.27 3.30 100.68 1.81 66.17 13.78 13,230
<br /> S 2,86 0.87 3.80 116.82 1.96 69.44 10.83 1,230
<br />.6 T 6.32 1.62 2.63 77,11 L66 47.24 13.47 9,360
<br /> G 3.97 1.21 3.96 120.40 1.99 60.66 12.10 9,360
<br /> S 4.03 1.23 3.62 107.29 1.87 67.00 14.19 9,360
<br />'6 C 9.80 2.99 2.33 71.02 1.47 44.81 22.80 14,271
<br /> T 9.54 2.91 2.40 73.16 L60 46.72 22.84 14,271
<br /> G 4.66 1.39 3.20 97.54 1.78 54.26 14.66 14,271
<br /> S 4.40 1.34 3.60 106.68 1.87 67.00 16.40 14,271
<br />17 C 14.47 10,948
<br />.8 S 6.80 1.77 3.60 106.68 1.87 67.00 20.30 14,270
<br />'9 S 6.60 1.68 3.40 103.63 1.64 66.08 18.70 11,634
<br />110 S 6.60 1.68 3.60 106.68 1.87 67.00 19.26 13,126
<br />.11 S 6.70 1.74 3.60 106.68 1.87 67.00 19,96 13,024
<br />112 S %.03 L63 3.40 103.63 1.84 66.08 17.11 11,743
<br />Monolith C 2.16 0.68 1.96 69.44 1.31 39.96 4.21 7,060
<br /> T 1.71 0.62 1.87 67.00 1.27 38.84 3.08 7,050
<br /> G 1.18 0.36 1.97 60.06 1.32 40.23 2.32 7,050
<br />. C-Concrete
<br />T-Turf
<br />G-{lravcl
<br />S-Stccl
<br />
<br />surface condition significantly impacts the product
<br />number at toppling for the 0.005 slope tests. The mono-
<br />lith toppled at product numbers of 2.32 and 4.21 on a
<br />loose gravel and concrete surfaces, respectively, When
<br />the flow velocity exceeded 1 fps (0.305 m3/s) the mate-
<br />rial under the edges of the monolith was eroded, which
<br />reduced the footing area and monolith stability.
<br />It is observed that a larger product number was re-
<br />quired to topple the monolith on the 0.005 slope than on
<br />the 0.015 slope for a similar test surface. The lower
<br />product numbers that result from the 0.015 slope are
<br />attributed to the point through which the monolith
<br />weight acts. When the monolith is sitting horizontal,
<br />the weight acts through the centroid down through the
<br />center of the foundation. However, as the slope in-
<br />creases, the weight continues to act through the foun-
<br />dation, but at a location closer to the downstream edge
<br />of the monolith, The result is that as the bed slope in-
<br />creases, the product number necessary to topple the
<br />monolith decreases,
<br />
<br />In an attempt to verilY the analysis, the depth and
<br />velocity values at which the 117.5 lb monolith toppled
<br />in the laboratory experiments for both the 0.005 and
<br />0.015 slopes with concrete surface was plotted on the
<br />hazard envelope as shown in Figure 2. For a channel
<br />slope of 0.005, the flow velocity of 2.16 feet per second
<br />and flow depth of 1.95 ft plotted adjacent to the toppling
<br />envelope curve. When the channel slope was 0.015, the
<br />flow velocity was 1.40 feet per second and the flow
<br />depth was 2.11 ft, plotted immediately outaide of the
<br />toppling envelope curve. The discrepancy of the point
<br />obtained from the 0.015 slope may be due to the slight
<br />difference in the monolith weight, 117.5Ibs, and the
<br />theoretical analysis performed with an ideal weight of
<br />120 lbs. Further, the monolith was tested on the 0.005
<br />slope first resulting in a slight wearing of the down-
<br />stream edge of the monolith base. The slightly worn
<br />edge may have contributed to a premature toppling. It
<br />is evident that the toppling envelope curve developed
<br />
<br />885
<br />
<br />WATER RESOURCES BULLETIN
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