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Assessing Stream Channel Stability At Bridges in Physiographic Regions

7. CONCLUSIONS

The stream stability assessment method developed here provides a self-contained, preliminary assessment of channel stability conditions as they affect bridge foundations. This method provides a quick assessment of conditions for the purpose of judging whether a more extensive geomorphic study or complete hydraulics (HEC-20, Level II) and sediment transport analyses (HEC-20, Level III) are needed to assess further the potential for adverse conditions developing at the bridge. As such, the method assists in decisionmaking with respect to bridge design, repair, rehabilitation, or replacement.

Although the stability assessment method was developed for use in any physiographic region in the United States, it was not possible to make observations within every region. In addition, it was not possible to sample every stream type and stream order within each region. Therefore, the method should be used cautiously and with questioning so that the results represent the stability at the bridge-stream intersection.

The results of this project provide a simplified methodology for assessing channel stability at bridge-stream intersections. It is intended to be used by qualified bridge inspectors and hydraulic engineers. This method developed is self-contained and does not require any other data or formal method of data collection other than the descriptors given in table 8. However, field forms were developed based on Thorne to help observers focus attention on specific aspects of a stream, make consistent observations, and record the observations systematically. (2) A photo album of the bridges in this study is provided in appendix A.

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