New Techniques for Aquatic Habitat Modeling

Assessments of stream aquatic habitat have often included water characteristics, such as depth and velocity, derived from numerical flow models. These simulations were only possible over longer stream segments using simplified 1D models, while computational burdens constrained more realistic 2D models to much shorter channel reaches. Both 1D and 2D models were often further limited by a lack of digital topographic data with resolution and accuracy sufficient to properly define the boundary conditions of the numerical flow domains. Recent advances in surveying technology, more efficient flow algorithms, and the availability of faster computers have begun to mitigate these issues and open opportunities for improved habitat appraisals. We combine detailed stream bathymetry, mapped by the Experimental Advanced Airborne Research Lidar (EAARL), with 2D fluid dynamics and aquatic habitat models to investigate the level of risk posed to spawning habitat of threatened fish species by altered flow characteristics in an evolving climate in a central Idaho stream. Results indicate that predicted climate-change induced variations in the annual hydrograph may have only small effects on spawning habitat in low-gradient unconfined headwater streams.