Predicting Velocity Frequency Distributions in Stream Reaches

Abstract

The quantification of management impacts on fish populations requires a reliable estimation of the local hydraulic habitat variability. In the case of complex natural flows, deterministic hydraulic models are expensive and not adapted to the description of local velocities. Statistical descriptions of the velocity distribution as a function of easily obtained input variables are therefore an attractive alternative. Existing velocity data on several French stream segments with intermediate-to large-scale roughness were analyzed statistically to define a shape parameter of the point velocity frequency distributions. Dimensional analysis was used to model this shape parameter, and thereby the velocity distributions, as a function of simple average descriptors of stream reaches (discharge, mean roughness, mean depth, and mean width). Such predictive models of the physical habitat availability for fish in the probability domain can provide stream managers with cost-effective decision tools. low-flow conditions, because of the violation of the common assumptions of uniformity and the unpredictability of turbu-2367 2368 LAMOUROUX ET AL.: PREDICTING VELOCITY FREQUENCY DISTRIBUTIONS LAMOUROUX ET AL.: PREDICTING VELOCITY FREQUENCY DISTRIBUTIONS 2369

Intercontinental Convergence of Stream Fish Community Traits along Geomorphic and Hydraulic Gradients

“…In our study, streams of France and Virginia had similar ranges of Froude numbers, even though reaches in Virginia were generally narrower, shallower and slower flowing (see Methods). This variable also integrates the spatial diversity of point hydraulic variables (bottom shear stress, current velocity) in stream reaches (Lamouroux et al 1992(Lamouroux et al , 1995. Therefore, our results indicate that dimensionless physical variables reveal common properties of systems of different sizes, and are potential predictors of ecological similarities in these systems (Statzner et al 1988, Heede andRinne 1990).…”

Aquatic Habitat Modeling in Running Waters

“…While empirical models of variation in broad morphometric channel variables have been in existence for many years, it is only recently that these statistically based techniques have been applied to model habitat hydraulics at the reach or "mesohabitat" scale. It has been suggested that at the reach scale, statistical hydraulic models can provide estimates of the frequency distribution of hydraulic variables, when given simple inputs such as mean river velocity, depth, and width (Lamouroux et al 1995(Lamouroux et al , 1999. Statistical techniques have shown that consistent patterns of such distributions appear among different streams.…”

Aquatic habitat modelling: biological validations of IFIM/Phabsim methodology and new perspectives

“…Simplified alternative to Phabsim, supported by statistical analysis of about one hundred Phabsim (Evha for the French version) study sites simulations Lamouroux et al (1995Lamouroux et al ( , 1998 demonstrated that hydraulics variables distributions like velocity or depth can be derived from reach values of hydraulic geometry. In the logical extension of these works, the idea of similar results with the common outputs of Phabsim modelling (i.e.…”

“…They are based on hydraulic statistical models (Lamouroux et al 1992(Lamouroux et al , 1995 coupled with local multivariate fish habitat models described above. The hydraulic statistical models are tools that predict the frequency distribution of velocity or depth in a stream reach with a simplification of the physical measurements.…”