Applying spatial hydraulic principles to quantify stream habitat

Abstract

Flow complexity plays an important role in stream ecology. Yet, a paucity of research exists with regard to quantifying flow complexity and relating it to the habitats that aquatic organisms utilize. Here we provide a generalized example of how twodimensional (2-D) numerical hydraulic models and spatial hydraulic metrics can be used to simulate and quantify biologically important flow patterns within streams. A detailed topographic survey, incorporating meso-scale topographic features (e.g. exposed boulders and bedrock outcrops) is performed for a small urbanized stream. The 2-D hydraulic model RMA2 is then used to model the flow conditions within the stream reach. Model results demonstrate that the meso-scale topographic features create highly complex flow patterns of potential biological importance. Recently developed spatial hydraulic metrics, based on hydraulic engineering principles (vorticity, circulation and kinetic energy gradients), are then used to quantify the various types of flow complexity found within the stream reach. In particular, spatial hydraulic metrics are used to quantify the stream reach's overall flow complexity and the flow complexity surrounding three chub mounds. A method for uniquely characterizing circulation zones is then developed and applied to five circulation zones within the study reach. The principles used in performing this study's topographic survey, spatial explicit hydraulic modelling and spatial hydraulic analyses, form a general framework for quantifying flow complexity in any stream. The ways in which using hydraulic models and spatial hydraulic metrics can help establish better habitat suitability criteria and design best management practices for use in stream and catchment area restoration projects is discussed.

Assessing hydrodynamic space use of brown trout, Salmo trutta, in a complex flow environment: a return to first principles.

“…Conallin et al, 2014) to the outputs of numerical modelling of complex flows (e.g. Crowder and Diplas, 2006). Unfortunately, the variables used tend to lack biological realism because they provide a poor indirect proxy for some more ecologically relevant factor, while the approaches employed frequently fail to account for multiple confounding variables.…”

The development of hydraulic and geomorphic complexity in recently formed streams in Glacier Bay National Park, Alaska

“…Changes in the diversity and complexity of hydraulic features have been found to influence habitat and species diversity (Maddock, 1999;Bartley and Rutherford, 2005;Sullivan et al, 2006), contributing to increased biodiversity within the stream environment (Stalnaker and Waddle, 1996;Crowder and Diplas, 2006;Dyer and Thoms, 2006;Principe et al, 2007). In comparison, little research has focussed on how changes in geomorphic diversity and complexity influence habitat availability within the aquatic environment (Yarnell et al, 2006).…”

Hydraulically related hydro‐morphological units: description based on a new conceptual mesohabitat evaluation model (MEM) using LiDAR data as geometric input

“…Their approach was compared with parallel ecological research on mesohabitats and functional habitats. Modelling variable discharges using two-dimensional depth-averaged numerical modelling was applied in the work of Crowder and Diplas (2006). Their results demonstrate that the meso-scale topographic features create highly complex flow patterns of potential biologic importance.…”