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Ecohydraulics & Habitat Heterogeneity

Habitat heterogeneity is thought to be an important feature of aquatic ecosystems, but specific metrics for designing habitat heterogeneity in restoration and assessing it from observations or simulations are lacking. With this on-going research we are exploring the incorporation of habitat heterogeneity into spawning habitat rehabilitation designs with (SHIRA).

Although optimal spawning habitat as defined by habitat suitability models is generally found in riffles, proximity of habitat to structural cover (pools, large woody debris, boulder clusters and overhanging vegetation) and hydrodynamic shear zones provide equally important refuge from predation and resting zones for energy conservation.

Increased heterogeneity at enhancement sites on the Mokelumne River appeared highly effective in terms of redd utilization with 70 redds located in close proximity to 93% of the available structural cover, and 42 redds located in close proximity to 90% of the available shear zone refugia. Partial results emphasizing habitat heterogeneity availability and utilization metrics were presented at the Ecohydraulics Symposium (see paper) to illustrate their potential in rehabilitation design and assessment.
Distribution of observed chinook redds at an spawning bed enhancement site on the Mokelumne River, overlaid on a 2D hydrodynamic model depth solution. ©2002 Wheaton (See Figure Copyright Disclaimer before downloading).


There are two strands I would like to pursue to continue this research:
  • First, I would like to expand the empirical data collection effort (i.e. redd surveys) to a mix of dynamic and regulated rivers to see if similar trends to what was found on the Mokelumne emerge.
  • Secondly, using this empirical backbone, I would like to incorporate the habitat heterogenity proximity measrurements into an ecohydraulic model I am developing.