Updated Condition Assessments in 2023 for Oak Creek and Pleasant Creek, Capitol Reef National Park

Schook, Derek; Wagner, Joel; Martin, Michael; Taliga, Chris

An evaluation of fluvial processes on the Fremont River near Holt Orchard confirms that recent channel migration will likely continue and cause further loss to the historic landscape. With substantial investment, bank stabilization is likely achievable in this setting, though it would be challenging because of the long two-part meander, flashy river flows, dry climate, and non-cohesive soils. Traditionally engineered hydraulic structures usually stabilize eroding banks when properly designed and emplaced. This hardened stabilization approach generally impedes ecosystem processes and transfers erosional forces elsewhere, and the cost may exceed $1,000,000 based on recent emergency riverbank stabilization work along State Route 24 in CARE. Alternatively, a robustly developed bioengineering treatment may also resist further orchard loss. Bioengineering would also require substantial financial and technical investment, but this approach would function somewhat more naturally and provide more habitat. A bioengineered solution takes time for vegetation to mature and achieve maximum bank protection, and the approach carries a greater risk than traditionally engineered structures. A third approach, which could be combined with the others, is channel realignment to reduce stream energy against the banks. Any of these action alternatives would require further evaluation and design, careful execution, monetary investment, and follow-up monitoring with adaptive management. In contrast, selecting a no-action alternative will result in losing some more of the historic orchard that is located on the river terrace. The extent of the loss is not readily predictable, but some/much of the orchard is likely to persist for centuries. The process of streambank erosion is simultaneously destructive and beneficial because it dissipates hydraulic energy and creates landforms, rejuvenating the riparian ecosystem. This no-action alternative is a preferable approach for maximizing ecosystem function, and it could be combined with monitoring future bank erosion and an adaptive management plan. The management decision of how to address the channel migration at Holt Orchard could include comparing the relative cost and values of bank stabilization versus preserving dynamic ecosystem processes. The objective of this Technical Assistance Report is to further inform this decision process.