Rock Stream Stability Structures in the Vicinity of Bridges.

摘要

This report was sponsored by the Utah Department of Transportation (UDOT) to determine if rock stream stability structures could be used as scour countermeasures and to protect streambanks. Traditional scour countermeasures, such as rock riprap, are effective in minimizing erosion but may not provide the best aquatic habitat. UDOT is interested in finding countermeasures that are effective in minimizing erosion at design flows and also benefit the aquatic habitat. David Rosgen, a specialist in fluvial geomorphology, has developed restoration structures that are friendly for aquatic habitat and also provide streambank protection and stream stability. These structures are the J-Hook Vane, Cross-Vane and W-Weir. Based on the findings outlined in this report, Cross-Vanes and W-Weirs can help protect bridges because they will protect both sides of a streambank while also providing grade control of the streambed. For stream stability structures to withstand design flows and shear stresses experienced near bridges, they should follow the design guidelines specified in this report. One of the most important design guidelines is that the structures discussed in this report have an attached portion of floodplain where the structure meets the stream bank. This portion of floodplain area can help to disperse the energy of the flow, thereby reducing shear stresses at abutments. Cross-Vanes and W-Weirs can help protect bridges and other infrastructure against scour by reducing shear stresses at piers and abutments at the design flood event. To further investigate their use as a scour countermeasure, it is recommended that this type structure be installed near a bridge following this report’s design criteria.UDOT believes that Cross-Vanes and W-Weirs should not be used as a primary scour countermeasure and that rock riprap (or other equivalent structural countermeasure) should be used as the primary protection for bridge foundations, abutments and piers.