Trip report detailing assessment of a hydraulic drop structure at the confluence of the Paria River and Water Canyon

Martin, Mike

he purpose of this site visit was to evaluate the overall stability, associated geomorphic conditions, and possible repair/replacement options of a large, hydraulic drop structure constructed at the confluence of the Paria River and Water Canyon in Bryce Canyon National Park (Figure 1). Downstream channel incision of the Paria River has undermined the lower portion of the structure and it appears that it could be completely lost in the future if no action is taken. This report summarizes our field observations, describes the immediate geomorphic setting, and presents an evaluation of the structure’s condition. Although we conclude that undertaking some type of repair is essential to maintain the structure and protect the nearby infrastructure, developing a specific engineering treatment was beyond the scope of this visit. We suggest that local engineers, which have expertise with this type of hydraulic structure and these river conditions, be consulted for specific treatment strategies. However, WRD will be available to interact with any design engineers or other interested parties in order to follow NPS objectives.