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Hydraulic Modeling of In-channel Habitats in the Ozark Highlands of Missouri:  Assessment of Physical Habitat Sensitivity to Environmental Change


by Maria S. Panfil and Robert B. Jacobson



The spatial and temporal variability of stream flow challenges scientists' ability to inventory in-stream habitats and assess their sensitivity to environmental changes.  This document describes a method for in-stream physical habitat inventory based on two-dimensional finite element hydraulic modeling, a Froude number and depth based habitat classification system, and a Geographic Information System.  The approach is applied to the Ratcliff Ford reach of the Jacks Fork River, Missouri, USA in order to assess the sensitivity of in-stream habitats to climatically induced hydrologic variation.  Modeling results for 31 discharges (0.4-78.5 cms) are presented in three ways: as plan-view maps of depth, velocity, Froude number, and habitat distribution; as contour plots of bivariate distributions of depth and velocity, and as summations of habitat abundance in wet and dry climatic regimes.  Modeling results indicate non-linear, divergent relationships between discharge and habitat areas.  Race-like conditions with intermediate Froude numbers (Fr# = 0.2-0.4) dominate channel conditions at higher discharges while pools and glides (Fr# = 0.1-0.2) dominate channel area at lower flows.  Comparisons of habitat duration curves for wet and dry climatic regimes suggest that most of the net loss of habitat area in dry years is accommodated at Ratcliff Ford by a loss of race and riffle habitat.  Pool and glide habitats may be less sensitive to hydrologic variability because the canyon-like nature of the Ratcliff Ford reach maintains deep, narrow pools over a wide range of discharges.


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Table of Contents

  • Introduction and Background

    • Figure 1.1 -- Overview of factors influencing in-stream habitat.
    • Figure 1.2 -- Map of the Ozark Highlands.
    • Figure 1.3 -- Map of the Jacks Fork Basin.
    • Figure 1.4 -- Map of the Ratcliff Ford Study Reach.
    • Figure 1.5 -- Photographs of the Ratcliff Ford Study Reach.
    • Table 1.1  -- Hydrologic characteristics for the Jacks Fork River at continuous streamflow gaging stations and at the Ratcliff Ford study reach.
  • Methods

    • Figure 2.1 -- Graph of annual mean flow records for Eminence, 1921-1996.
    • Figure 2.2 -- Hydrographs and flow duration curves for years representative of wet and dry climate scenarios.
    • Figure 2.3 -- Regression plot relating gaged flow records at Eminence to flows at Ratcliff Ford.
    • Figure 2.4 -- Extrapolated wet scenario, dry scenario, and mean flow duration curves for Ratcliff Ford.
    • Figure 2.5 -- Maps of bed topography and roughness input into the finite element mesh.
    • Figure 2.6 -- Illustration and graph of the habitat classification scheme used to classify model output.
    • Table 2.1  -- Habitat areas for the range of discharges modeled.
    • Table 2.2  -- Depth and Froude number criteria for the habitat classification system.
  • Results and Discussion

    • Figure 3.1 -- Maps of model output of depth, velocity, Froude number, and habitat; discharges 78.5-0.4 cms.
    • Figure 3.2 -- Contour plots of bivariate distributions of depth and velocity; discharges 78.5-0.4 cms.
    • Figure 3.3 -- Graphs of discharge vs. habitat area.
    • Figure 3.4 -- Habitat duration curves for wet and dry climate scenarios.
    • Figure 3.5 -- Graph of average daily habitat areas for wet and dry climate scenarios.
  • Conclusion

  • References

  • Appendices

    • A.1 -- The Ozarks Stream Geomorphology Project.
    • Figure A1.1 -- Flow chart summarizing factors that influence stream morphology and aquatic communities.
    • A.2 -- Stream surveying and biological sampling.
    • A.3 -- Derivation of the regression relationship between flows at Eminence and Ratcliff Ford.
    • Figure A3.1 -- Comparison flow duration curves between three USGS streamflow gaging stations in the Jacks Fork basin.
    • A.4 -- Derivation of the stage/discharge relationship for Ratcliff Ford.


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Last Modification: 02/02/05