Dr. Vince Neary
Department of Civil and
Environmental Engineering
Tennessee Technological University
Prescott Hall 339
1020 Stadium Road, Box 5015
Cookeville, TN 38505-0001

Tel: (931) 372 3604
Fax: (931) 372 6239

Our Research

Wetlands Research

Collaborators:
Dr. V.S. Neary (TTU, Civil Engineering), A. Jason Hill (TTU, Civil Engineering), Dr. Tom Roberts (TTU, Biology), Ken Morgan (Biology), Dr. Jie Cui (TTU, Mechanical Engineering)



Forested Depressional Wetland, Highland Rim, Middle Tennessee
(Photo V.S. Neary, November 20, 2003).


Wetlands are considered one of the most important hydrologic systems in our biosphere, but are threatened by human development. The water resources group at TTU is working on several fronts to provide regulators and wetland managers with better guidance and improved assessment tools for wetland preservation, mitigation, construction, monitoring and management. Current research includes: (1) Modeling vegetated flow resistance in wetlands and rivers; (2) Hydrologic modeling for wetlands; (3) Functional assessment modeling for wetland hydrology.


Vegetated Flow Resistance
The assessment of vegetation effects in waterways is increasingly important with the shift to ecological approaches to river and wetland engineering and restoration, and other water management practices that value the benefits of vegetation to aquatic and riparian habitat, biota and water quality (Stoesser et al. 2004). Vegetation causes flow resistance mainly as form drag and dramatically affects local flow, turbulence, and mixing properties. It aids sediment deposition while reducing the entrainment capability of sediment into suspension and plays a major role in fluvial geomorphic processes (Simon et al. 2004). Pronounced flow inhomogeneities and coherent structures affect momentum fluxes within vegetation zones and the vegetation-water interface, which in turn affect scalar fluxes that govern oxygen and nutrient exchange, seed dispersal, sediment deposition, and chemical reactions in vegetated zones.We are evaluating the performance of computational fluid dynamics models to simulate the effects of vegetation on open channel flow: A model based on solution of the Reynolds averaged Navier-Stokes (RANS) equations, which calculates the temporally averaged flow field; and a large eddy simulation (LES) model that solves the unsteady Navier-Stokes equations to calculate the instantaneous flow field. The objectives of this preliminary study are: (1) To validate the models with experimental measurements reported in the literature for simulated rigid plant stems in laboratory flumes; (2) To identify measurement data needs for improved model validation; (3) To compare model simulations of flow through channels with and without vegetation; (4) To identify the limitations with the present RANS and LES modeling approaches.




Instantaneous flow field predicted by LES indicating Kelvin-Helmholtz vortices in the centerplane
of the channel (xz plane) for case R31 Shimizu and Tsujimoto 1994.



References
Simon, A., S.J. Bennett, and V.S. Neary (2004) "Riparian vegetation and fluvial geomorphology: Problems and opportunities." In: Riparian Vegetation and Fluvial Geomorphology, edited by S.J. Bennett and A. Simon, Water Science and Application Series Volume 8, p. 1-10, American Geophysical Union, Washington, D.C..

Stoesser, T., V.S. Neary, and C.A.M.E. Wilson (2004) "Modeling Vegetated Channel Flows: Challenges and Opportunities." IASME/WSEAS International Conference on FLUID MECHANICS (FLUIDS 2004), Special Session Eco-hydraulics: State-of-the-Art and Future Directions, Corfu Island, Greece, August 17-19, 2004

Neary, V.S. (2003) "Numerical solution of fully-developed flow with vegetative resistance." Journal of Engineering Mechanics. 129(5), 558-563.

Cui, J. and V.S. Neary (2002) "Large eddy simulation (LES) of fully developed flow through vegetation." IAHR's 5th International Conference on Hydroinformatics, Cardiff, Wales, July 1-5, 2002.


Functional Assessment Model Development
The importance of hydrology to the establishment and maintenance of wetland ecosystems is widely recognized. Hydrology strongly influences plant community development and chemical transport and transformation in wetland ecosystems. Therefore, tools to assess wetland hydrologic conditions are critical to the successful management of wetland resources. The hydrogeomorphic (HGM) approach to wetland classification and functional assessment was developed to facilitate rapid assessment of wetland functions in a regulatory context. The aim of our research is to strengthen current functional assessment model development using the HGM approach by through hydrologic modeling. A forested depressional wetland, representative of seasonally inundated depressions on the Tennessee Highland Rim (Roberts et al. 2004), is being monitored extensively to support model development, calibration and validation. The hydrologic model is being used to simulate functional response to a range of environmental conditions and development impacts (e.g., urbanization). The simulation results provide valuable insights into variable sensitivity and interaction and aid the development of improved assessment models. Future work will explore methods for assessing the uncertainty in functional capacity index scores and the implications for wetland management decision-making.



Simulated response to a decreasing variable subindex for each model variable (Left) and Comparison of simulated functional capacity index (FCI Actual) scores to those predicted with the assessment model (FCI Predicted) (Right).


References
Hill, A.J., V.S. Neary and K. Morgan (2005) "A hydrologic functional assessment model for depressional wetlands." Wetlands, 26(1): 161-180.

Roberts, T.H., K.L. Morgan, A.J. Hill, R. Cripps, and V.S. Neary Hydrogeomorphic Classification and Assessment of Depression and Flat Wetlands at Arnold Engineering Development Center (AEDC), Final Report Prepared for AEDC, June 2004, 169 pages including appendices.

Hill, A.J. and V.S. Neary (2004). Regional Guidebook for Flat and Depressional Wetlands on the Tennessee Highland Rim: Hydrologic Function, Prepared for AEDC, June 2004, 48 pages.

Hill, A.J. and V.S. Neary (In Review). "Hydrologic Modeling as a Development Tool for HGM Functional Assessment Models." Wetlands.


Wetland Hydrology Monitoring and Modeling
Long-term high-resolution hydrologic monitoring data for depressional wetlands is scarce at best. In 2001, a monitoring program was initiated for a depressional wetland in Algood, Tennessee. Instrumentation at the Algood wetland includes two weather stations, numerous piezometer nests and monitoring wells, a water level recorder, a network of rain gauges measuring both gross and net precipitation, stem-flow collars, soil moisture sensors, and flow gauges for measuring surface runoff. The detailed field measurments are supporting efforts to develop hydrologic and functional assessment models for depressional wetlands.



Topographic Map of Algood Wetland showing the location of Monitoring Equipment



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