The hydro-morphological index of diversity: a tool for describing habitat heterogeneity in river engineering projects

Abstract

We present a new hydro-morphological index of diversity (HMID), a tool aimed for use in river engineering projects and firstly developed at gravel-bed streams in Switzerland, but intended for a broader use. We carried out field work with extensive hydraulic and geomorphic data collection, conducted correlation analysis with hydro-morphological variables, formulated the HMID, and analyzed the correlation between HMID and a visual habitat assessment method. The HMID is calculated by means of the coefficient of variation of the hydraulic variables flow velocity and water depth, which have been demonstrated to sufficiently represent the hydro-morphological heterogeneity of alpine gravel-bed stream reaches.Based on numerical modeling, the HMID can be calculated easily for a comparison of different alternatives in river engineering projects and thus achieves predictive power for design decisions. HMID can be applied at a reach-related scale in engineering programs involving geomorphic measures that aim at the enhancement of habitat heterogeneity of a stream. However, the application of HMID has to be integrated with evaluations of the long-term streambed evolvements that are considered at a catchment scale and strongly related to the sediment regime of the stream under study.

A case study on spatial and temporal hydraulic variability in an alpine gravel‐bed stream based on the hydromorphological index of diversity

“…To further evaluate spatial variability, we chose mean values, coefficient of variation (CV) of the hydraulic variables and a recently proposed hydro-morphological index of diversity (HMID) (Gostner et al, 2012) that is also CVbased. CV is an adjusted measure for standard deviation and therefore a better comparative measure of variability (Schneider, 1994) and commonly used in temporal and spatial analysis of ecological patterns (Rossi et al, 1992;Simonson et al, 1994;Gubala et al, 1996;Palmer et al, Figure 4.…”

“…The hydraulic environment is composed by hydraulic variables such as flow velocity and water depth, which are the result of the interplay between the morphological template and the hydrological regime. Recently, it was demonstrated (Gostner et al, 2012) that the hydraulic variables flow velocity and water depth and, in particular, their variance are highly correlated to other physical factors believed to be critical for aquatic biota, such as bottom shear stress or substrate characteristics. Recently, it was demonstrated (Gostner et al, 2012) that the hydraulic variables flow velocity and water depth and, in particular, their variance are highly correlated to other physical factors believed to be critical for aquatic biota, such as bottom shear stress or substrate characteristics.…”

“…In this study, we focused our efforts on implementing a numerical two-dimensional (2D) hydrodynamic model of the study reaches and analysing spatial and temporal variability on the basis of statistical parameters of hydraulic variables and a recently proposed hydromorphological index of diversity (HMID) (Gostner et al, 2012). Thus, we were able to (i) elucidate hydraulic variables as a result of the interplay between both hydrological and morphological conditions that make up the physical habitat, (ii) analyse not only spatial but also temporal variability of the studied variables and (iii), by applying the HMID, avoid a time-consuming elaboration of species-specific preference curves that are subject to uncertainty and require validation.…”

Land‐use legacy and the differential response of stream macroinvertebrates to multiple stressors studied usingin situexperimental mesocosms

“…Habitat heterogeneity is an important stream ecosystem feature, as variation in substratum type and hydro-morphology result in a multitude of different habitat niches (Gostner et al, 2013). Habitat heterogeneity is an important stream ecosystem feature, as variation in substratum type and hydro-morphology result in a multitude of different habitat niches (Gostner et al, 2013).…”

Preface: physical template and river ecosystem functioning: interdisciplinary feedbacks for improving rivers

“…Based on extensive hydraulic and geomorphic data collected in alpine rivers, Gostner et al (2012) present a new hydromorphological index based on the coefficient of variation of the flow velocity and the water depth. It can be linked to standard modelling and is especially designed to enable the prediction and comparison of different alternatives in river engineering projects to support decision making processes towards an enhancement of habitat heterogeneity.…”