| To restore ecological processes and functions, we must advance our knowledge of natural stream flow fields and their influence on aquatic ecosystems. This research addressed this need by meeting the following objectives: Objective (1) (a) Evaluate the adequacy of existing empirical relationships for describing natural stream flow fields and (b) investigate spatial distributions of flow variables; Objective (2) Test the adequacy of ADCP instruments for measuring velocity, shear stress, and turbulence distributions in cobble bed streams; Objective (3) Investigate temporal variations in periphyton resistance to shear stress.; Objective 1 was completed by conducting acoustic Doppler velocimeter (ADV) measurements in two stream reaches. Objective 2 was met by collecting ADCP and ADV data at nine coincident stations and statistically comparing the results. Objective 3 was met by colonizing periphyton assemblages on ceramic tiles in a stream and exposing the collected tiles to various levels of shear stress in a laboratory flume.; The results showed that existing empirical relationships were adequate for describing velocity and shear stress distributions, but empirical predictions of turbulence parameters were significantly different from observed values. The ADCP adequately measured velocity magnitude and shear stress values, but not three dimensional velocity components or turbulence parameters. Periphyton resistance to shear stress increased with successional development of the assemblage, but was not affected by time of the growth season.; The results have broad implications for evaluating and managing aquatic systems. The flow field measurements reveal that we must re-evaluate natural stream turbulence prediction techniques. Quantifiable descriptions of flow heterogeneity will improve restoration designs and communication between disciplines. Further, this data can be used for parameterization of numerical models. ADCP results verify the use of these instruments for velocity and shear stress measurements. This has implications for habitat evaluation, model calibration, sediment transport estimates, and evaluation of other stream processes. Results of the periphyton experiments can be used to improve reservoir release management, restoration designs, and assessment of instream flow requirements. |
