Monitoring Scour Critical Bridges (2009) / Chapter Skim
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39 CASE STUDIES OF EXISTING SITES The following case histories were selected for this report because they cover a range of geographical locations and types of fixed scour monitoring instrumentation. Alaska To better understand the scour process and to monitor bed elevation at bridge piers, the USGS and the Alaska Department of Transportation and Public Facilities operate a network of streambed scour monitoring stations in Alaska (Conaway 2005, 2006a, b)
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40 to the Caltrans central office in Sacramento. The existing devices include four different types of communication systems including (1)
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41 occurred at one of the yellow flag float-outs; it floated out as designed and a telephone call was triggered. However, it was not possible to tell which specific pier had scoured.
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including sending false alarms and not protecting investment in the infrastructure. In a discussion regarding the performance of the scour monitors, Caltrans reported that, in general, the instruments perform well.
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43 the data logger. They attributed the difference in measurements to the geometry of the echo reflection point area (because of its conical shape)
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44 FIGURE 41 Remote station and conduit to sonar monitor at Wantagh Parkway over Sloop Channel, Long Island. FIGURE 42 Elevation of Robert Moses Causeway over Fire Island Inlet, Long Island (Copyright: Raimondo di Egidio)
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FIGURE 45 Adjustable sonar bracket prior to underwater installation on Wantagh Parkway over Goose Creek, Long Island. 45 the failure, and they were designed, custom-built, and arrived at the site ten weeks later.
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46 FIGURE 46 General elevation of Klineline Bridge, Vancouver, Washington. FIGURE 47 Inspection photograph of exposed pier spread footing on the Klineline Bridge on Highway 99 over Salmon Creek.
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47 FIGURE 51 Conduit from sheet pile to tilt meter mounted on a pier of the Klineline Bridge. A water stage was installed to monitor flow, the rate of change of flow, and river depth changes.
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Alaska The Knik River near Palmer was the only site within the 20 bridge monitoring network (see Figures 32 and 33) that had large changes in bed elevation each year (Conaway 2006a)
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49 The cross section defined by the upstream bridge opening was surveyed periodically to document changes in bed elevation across the channel. These cross sections and the sonar data show an annual cycle in channel change.
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Georgia The Georgia DOT report contained information on observed scour at three of four bridges monitored during their 2-year study (Sturm et al.
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