Sedimentological and Biological Analyses on Hobble Creek Prior to Restoration Sedimentological and Biological Analyses on Hobble Creek Prior to Restoration

by Brown, Jaron Michael

Hobble Creek is one of several inflowing streams and rivers into Utah Lake, Utah, USA. Historically, June sucker (Chasmistes liorus), a federally listed endemic fish, spawned up all the major inflowing streams and rivers but is now limited to just the Provo River. The State of Utah has recently proposed restoring the lower reaches of Hobble Creek for additional spawning and rearing needs. This restoration effort will likely involve removal of migration barriers, re-aligning the stream, and removing existing levees that prevent floodplain access. These changes have raised several questions that this study aims to answer. First, what are the sediment transport rates under current flow conditions in Hobble Creek, and how well do various predictive models match the actual rates? Secondly, assuming a successful introduction of adult June sucker into the Hobble Creek system, will the existing flow regime be capable of transporting the fry to an area adequate for successful population growth?

Four bedload predictive models were used to create sediment rating curves for flows typically found in Hobble Creek: the Meyer-Peter, Muller equation (MPM), Wilcock’s two parameter model, Rosgen’s Pagosa reference curve, and Bathurst’s Phase 2 equation. Each were used and compared to data obtained on Hobble Creek during the spring 2006 snowmelt runoff season. Results show that the uncalibrated MPM formula over predicted bedload rates by several orders of magnitude, while the Wilcock model sometimes performed more accurately, but was also prone to inaccuracies greater than an order of magnitude. The Rosgen and Bathurst predicted rates were consistently within an order of magnitude of observed rates.

Areas of optimal rearing potential were determined by separating the stream-lake interface into four zones: dense vegetation, sparse vegetation, open lake, and within the creek. These four zones were analyzed for rearing potential based on food resources, temperature patterns and existing small fish densities. Larval drift modeling was performed to characterize the ability of the stream to transport larvae to the zones studied. We found that highest food density occurs in the open lake; small fish were most abundant in the open lake as well. The open lake is also better for rearing habitat in terms of temperatures between zones. Furthermore, larval drift studies show that the current geometry and flow regime is incapable of transporting larvae to zones in the lake where food and warm water are both available, and that larvae are likely to die before reaching those areas.