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 vari- ables, formulated the HMID, and analyzed the corre- lation 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 demon- strated to sufficiently represent the hydro-morpholog- ical heterogeneity of alpine gravel-bed stream reaches. Based on numerical modeling, the HMID can be calculated easily for a comparison of different alter- natives in river engineering projects and thus achieves predictive power for design decisions. HMID can be applied at a reach-related scale in engineering pro- grams involving geomorphic measures that aim at the enhancement of habitat heterogeneity of a stream. However, the application of HMID has to be inte- grated 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.