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<br />Table 6.1 ASSESSING THE SCOUR POTENTIAL AT BRIDGES <br />1, UPSTREAM CONDITIONS <br /> <br />a. Banks <br /> <br />- Stable Natural vegetation, trees, bank stabilization ..asures <br />such as riprap, paving, gabions, channel stabilization <br />measures such as dikes and groins. <br /> <br />Unstable Bank sloughing, undermining, evidence of lateral <br />movement, damage to stream stabilization installation's, <br />etc. <br /> <br />b. Main Channel <br /> <br />Clear and open with good approach flow conditions, or ..andering or <br />braided with main channel at an angle to the orientation of the <br />bridge. <br /> <br />Existence of islands, bars, debris, cattle guards, fences that may <br />affect flow. <br /> <br />Aggrading or degrading streambed. <br /> <br />Evidence of 80vement of channel with respect to bridge (make <br />sketches, take pictures.) <br /> <br />c. Floodplain <br /> <br />Evidence of significant flow on floodplain. <br /> <br />Floodplain flow patterns - does flow overtop road and/or return to <br />main channel? <br /> <br />Existence and water adequacy of relief bridges (if relief bridges <br />are obstructed, they will affect flow patterns at the main channel <br />bridge. ) <br /> <br />Extent of floodplain development and any obstruction to flows <br />approaching the bridge and its approaches. <br /> <br />Evidence of overtopping approach roads (debris, erosion of <br />embankment slopes, damage to riprap or pavement, etc.) <br /> <br />d. Debris <br /> <br />Extent of debris in upstream channel. <br /> <br />54 <br /> <br />'I <br />I <br />(! <br />, I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />