Coupled Ecological and Hydraulic Approaches to Assess Potential Impacts on Habitat Suitability

Engineering projects in river environments may positively or negatively impact riparian habitat to varying degrees, contingent upon the nature of the project and design choices. Aquatic habitat remains an elusive parameter to fully consider during project design. Hydraulic conditions favorable to habitat vary across species, geographical location, and the literature. When specific conditions are available for a given species, they typically exist in the form of a habitat suitability index indicating predilections for a range of hydraulic or substrate conditions. Coupling habitat suitability indices with hydraulic parameters requires tools to estimate hydraulics for quantification of potential habitat impacts. Indices are commonly reported as a range of depth-averaged parameters, including flow depth, shear stress, or velocity magnitude; for many applications, the use of a two-dimensional numerical hydraulic simulation provides information on the scales needed for index comparison. This proceeding presents results of a practical application of habitat impact assessments for proposed river alterations to the Grand River, MI. Habitat for two critical species, the snuffbox mussel (Epioblasma triquetra) and the lake sturgeon (Acipenser fulvescens), is examined at existing and proposed conditions using a comprehensive literature review of habitat suitability indices, development of new indices based on field surveys, and application of computational fluid dynamics models. Results provide evidence of the power of coupled ecologic and hydraulic models to assess effects on aquatic habitat and serve as a design tool for overall riparian health.