HYDRODYNAMIC CHARACTERIZATION OF FRESHWATER MUSSEL HABITATS IN THE UPPER 
MISSISSIPPI RIVER.

Nathan Young, Larry Weber, and Tatsuaki Nakato.
IIHR – Hydroscience & Engineering, Department of Civil & Environmental 
Engineering, The University of Iowa, Iowa City, IA, 52242.

Human activities in the Upper Mississippi River Basin have caused a significant 
decline in freshwater mussel populations.  One contributing factor is the 
construction of navigation dams and river training structures on the main stem 
of the Upper Mississippi River (UMR).  These structures have resulted in the 
slowing and redirection of flow through the braided channel system, severely 
impacting mussel habitats.  The goal of the research described is to develop a 
more complete understanding of hydrodynamics within mussel habitats in hopes of 
providing information useful in the preservation and restoration of mussel 
populations in the UMR.  Research efforts will involve a comprehensive data 
collection program in Pool 16 of the UMR, characterizing hydraulics, water 
quality, and substrate in the reach.  Statistical treatment of the data will be 
used to correlate measured parameters with mussel density and habitat quality.

Methods will include collection and analysis of data describing the bathymetry, 
flow fields, water chemistry, sediment gradation and chemistry, and mussel 
location and density.  A bathymetric survey, begun in 2002, will define the 
geometry of the riverbed at reach and habitat scales.  Velocity data will be 
collected using acoustic Doppler velocimetry (ADV).  ADV measures time series of 
fine-scale three-dimensional velocities, allowing for a detailed description of 
velocity fields and useful in characterizing shear stress and turbulence.  Water 
quality, sediment, and mussel data will be collected using conventional methods.  
The use of side-scanning sonar is currently being investigated as a supplemental 
means of measuring substrate composition, locating mussel beds, and quantifying 
mussel density.

Bathymetric and velocity data will also be used to develop numerical simulations 
using computational fluid dynamics (CFD). Numerical simulation will provide a 
means of studying hydrodynamics under the wide range of flow conditions 
experienced by UMR species, as well as the relationship between scale and the 
influence of individual hydrodynamic parameters on habitat quality.

Keywords: Upper Mississippi River; bathymetric survey; freshwater mussels; 
hydrodynamics; habitat