loading page

The role of riverine bed roughness, egg pocket location, and egg pocket permeability on salmonid redd-induced hyporheic flows
  • +4
  • Bishal Bhattarai,
  • Brandon Hilliard,
  • William Jeffery Reeder,
  • Ralph Budwig,
  • Benjamin T. Martin,
  • Tao xing,
  • Daniele Tonina
Bishal Bhattarai
University of Idaho

Corresponding Author:[email protected]

Author Profile
Brandon Hilliard
University of Idaho
Author Profile
William Jeffery Reeder
University of Idaho
Author Profile
Ralph Budwig
University of Idaho
Author Profile
Benjamin T. Martin
Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam
Author Profile
Tao xing
University of Idaho
Author Profile
Daniele Tonina
University of Idaho
Author Profile

Abstract

Salmon spawning activities alter streambed morphology, forming a dune-shaped egg nest called a redd. The spawning process increases redd sediment hydraulic conductivity, KD, and congregates large sediment grains to form an egg pocket, such that egg pocket hydraulic conductivity, KEP, may be higher than KD. Salmon females may create one or more egg pockets within a single redd. Although the impact of redd shape and KD on redd-induced hyporheic fluxes has been studied, the effects of streambed roughness, R, egg pocket permeability, and egg pocket location on egg pocket hyporheic fluxes have not yet been quantified. This study investigates this knowledge gap with a set of numerical simulations supported by flume experiments. We simulated hyporheic flows for five egg pocket locations, five KEP values from 0.0025 to 0.02 m/s, and 12 rough streambed surfaces. Surface roughness was scaled from a measured streambed surface in two ways - only vertically (R1) and both vertically and horizontally (R2) - with scaling coefficients ranging from 0.5 to 3. The measured streambed surface had a median diameter, D50, of 1 cm and a standard deviation of 0.77 cm. The results indicated that the dimensionless flux into the egg pocket increases noticeably with the downstream distance of egg pockets from the redd pit, and less strongly with KEP*=KEP/KD. The near-surface downwelling fluxes significantly increase with R1, but only negligibly with R2, and for deeper egg pockets, flux into the egg pocket is minimally impacted by surface roughness.
26 Jun 2023Submitted to ESS Open Archive
08 Jul 2023Published in ESS Open Archive