Vegetative Resistance to Flow in the Everglades

Project Proposal for 2001

Project number: 4384-16300

Continuing Project Work Plan - FY 2001

IDENTIFYING INFORMATION
Co-Project Chiefs: Harry L. Jenter and Raymond W. Schaffranek
Region/Division/Team/Section: Eastern Region/Water Resources Division/Branch of Regional Research
Email: hjenter@usgs.gov, rws@usgs.gov
Phone: (703) 648-5916, (703) 648-5891
Fax: (703) 648-5484
Mail address: U.S. Geological Survey, 430 National Center, 12201 Sunrise Valley Drive, Reston, VA 20192

Project title: Vegetative Resistance to Flow in the Everglades
Ecosystem: South Florida
Project start date: October 1994
Project end date: September 2002

PURPOSE AND SCOPE:

Data fundamental to quantifying the effects that the highly variable vegetation of the Everglades has on shallow surface-water flows is lacking. Models presently being used to manage the ecosystem need to quantify the flow-resistance effects of vegetation in order to properly simulate flow. These management models have been forced to rely primarily on qualitative estimates and engineering judgments for the treatment and representation of vegetative flow resistance. The objectives of this project are: 1) to collect data to produce accurate values of flow-resistance coef-ficients for use in numerical simulation models, 2) to analyze these flow data to quantify the re-sistance effects of the submerged vegetation, 3) to investigate the vegetation/flow-resistance correlation in controlled laboratory experiments and in the field, 4) to isolate the key vegetation properties to which the evaluation of resistance effects can best be correlated, and 5) to derive expressions that can be used to more creditably represent these effects in numerical models. These findings can be used to establish the validity of management models presently in use throughout the entire Everglades ecosystem as well as to provide improved expressions for representing the resistance effects of vegetation on flow for incorporation in newly developed models.

SIGNIFICANCE TO RESTORATION:

Restoration and resource-management decisions affecting the south Florida ecosystem are based, in large part, on the results of numerical flow-simulation models. Scenario tests of management options are typically processed and evaluated using results from numerical flow models. Such simulation results are critically dependent on the particular treatment of vegetative flow resistance used in the numerical model. The resistance exerted on the shallow flow of the Everglades by the variably dense vegetation is one of the dominant but least understood forces affecting its movement. This project will benefit the restoration and management of the south Florida ecosystem by providing the fundamental information needed to better define and properly treat the resistance effects of vegetation on flow in management models. Comprehensive flow-resistance information is required in the management models used by the South Florida Water Management District (SFWMD), the Corps of Engineers (COE), and the National Park Service (NPS), among others, to ensure that appropriate conclusions affecting restoration actions are drawn from nu-merical simulation results. The design and operation of stormwater treatment areas (STAs), such as the prototype Everglades Nutrient Removal (ENR) Project for the removal of phosphorus from agricultural runoff, will be improved when the hydraulic models used to affect their design and operation incorporate improved expressions for treating vegetative resistance. Restoration and management decisions, based on numerical simulations produced by models such as the South Florida Water Management Model and others, likewise will be founded on more realistic simulations when improved expressions for treating flow resistance are incorporated. Hence, evaluation of restoration and management alternatives through the use of numerical model results will be more consistent, reliable, accurate, and, therefore, of greater credibility in the decision-making process.

METHODOLOGY:

Numerical models, remote-sensing techniques, and geographical-information-system tools are being used to analyze data, evaluate resistance coefficients, and develop empirical expressions to define the flow resistance of various types of vegetation found in the Everglades wetlands. Water-surface slope, flow velocity, and vegetation data have been collected to determine the flow-resistance effects of variably dense vegetation. Concurrent flow and vegetation data have been collected in an indoor flume under controlled laboratory conditions as well as throughout the Everglades wetlands.

Data collected in the USGS tilting flume at the Stennis Space Center, MS, are being used to de-termine the flow resistance of uniform stands of sawgrass. Experiments were conducted for five flow depths between 0.15 and 0.76 meters, for mean cross-sectional velocities between 0.15 and 5 cm/s, and for three plant densities. Hydraulic measurements of the water-surface slope and flow velocities were made during each experiment using modified hook gages and acoustic Doppler velocity (ADV) meters. The vegetation in the flume was sampled and characterized during each experimental series (Rybicki, et. al., 1999), each consisting of 20 to 40 experiments. The vegetation in the flume was sampled to determine, as a function of depth, the biomass per unit area, number of stems and leaves per unit area, leaf and stem widths, as well as other characteristics. Concurrent flow and vegetation data were also collected at numerous sites in Shark Valley Slough, Taylor Slough, WCA-2, and the ENR area for various types of plant communities including sawgrass, rush, cattail, and others, to supplement the laboratory experiments.

In order to collect the data needed to evaluate and develop flow-resistance expressions, a unique pipe-manometer method has been devised to determine the local water-surface slope in wetlands. The device is a 2.4-meter-long plastic pipe, 7.6 cm in diameter, with a 90-degree elbow at one end. The pipe is positioned in the water column parallel to the flow direction and an ADV meter equipped with a side-looking probe is used to measure the centerline flow velocity in the pipe. Knowing the flow characteristics of the pipe, the difference in the water-surface elevation at the ends of the pipe is calculated from appropriate expressions using the measured centerline flow velocity in the pipe. The pipe manometer is currently calibrated, and appears to hold great potential as an efficient, accurate method for the local measurement of the shallow water-surface slopes typical of the low-velocity, small-gradient flows in the Everglades.

ACCOMPLISHMENTS, OUTCOMES, AND PRODUCTS

FY 2000 project accomplishments:

The death of Dr. Jonathan Lee, the project chief, in December of 1999 prompted the need for development of new approaches to accomplish the project objectives that are identified in the revision of the FY 2000 Project Workplan and Budget developed by the new Project Chiefs. Steps have been taken by the Project Chiefs to ensure that the project commitments according to the original workplan are met and that significant findings and results are communicated to the scientific community in a timely manner. The following discussion reflects the content of the revised workplan and its impacts on the project budget.

All project laboratory and field datasets collected over the four-year duration of the project (1996-1999) were organized and catalogued by project personnel during December of 1999 and January of 2000 and have been analyzed throughout the remainder of the year to yield velocity profiles, depth-averaged velocities and Manning’s n values. Data from the laboratory, Shark Slough, Taylor Slough and Water Conservation Area 2A have been analyzed and tabulated. Summary reports describing these data sets are in preparation.

In the spring, contracts were initiated with Dr. Vincent Lai to complete the pipe manometer theoretical analysis and calibration and Dr. Lisa Roig to complete the vegetative resistance calculations for both laboratory and field data. Both of these contracts have been fulfilled as of October 2000. Draft reports from both contracts have been prepared and are being reviewed for publication. A full-time intern has been hired to assist both in data processing and report writing tasks.

All data pertaining to the calibration of the pipe manometer were processed during January and February of 2000. The data were turned over to Lai for evaluation in March 2000. In turn, Lai has provided the Project Chiefs with a draft report describing the theory of the pipe manometer, including definition of the limits of laminar, transitional and turbulent flow theory.

At the end of March, Roig initiated a literature review on the subject of vegetative resistance to flow using Lee’s files and notes as one source of reference information. This review is completed and serves as the foundation for her journal article as well as a precursor to her analysis of Lee’s laboratory and field data. It also serves as a valuable reference resource for others contributing to this project.

The project intern has assumed primary responsibility for the production of reports documenting the laboratory and field data for pipe calibration and flow-resistance computation. The intern, along with a Project Chief (Jenter), has published a USGS Open File data report describing the pipe manometer calibration data and procedure.

During March of 2000, the Project Chiefs assisted in the submission of two manuscripts co-authored by Dr. Lee and Dr. Mariano Guardo of the South Florida Water Management District. The first, a USGS Water Resources Investigation Report, has received USGS Director’s approval and should be published shortly. The second, a journal article, was submitted to Ecological Engineering in March of 2000, has been reviewed and is being rewritten by Dr. Mariano Guardo in response to the reviews.

FY 2000 scientific outcomes:

Major scientific outcomes for this project during FY 2000 include:

1. The theoretical limits of applicability of Lee’s pipe manometer method for computing water-surface slopes have been determined and defined. This allows other researchers to identify situations in which the pipe manometer technique can be used to accurately measure the local water-surface slope.

2. The pipe manometer calibration data show a distinct, nearly-linear variation between the pipe centerline velocity and the square root of the water surface slope. For the pipe manometer geometry used on this project in both the field and laboratory, this implies that the developed calibration is applicable throughout the range of velocities typically observed in the Everglades (Calibration data collected in the laboratory span the range 0.3 cm/s - 7.5 cm/s).

FY 2000 products completed or nearly completed:

Lee, J. K., Visser, H. M., Jenter, H. L. and Duff, M. P., 2000, Velocity and Stage Data Collected in a Laboratory Flume for Water-Surface Slope Determination Using a Pipe Manometer, U.S. Geological Survey Open-File Report 00-393.

Lee, J. K., Lai, C., and Jenter, H. L., (in review), A "Pipe-Manometer" Technique for Determination of Water-Surface Slope in Wetlands, to be submitted to professional society Journal - December 2000.

Lee, J. K., Jenter, H. L., Lai, C., Visser, H. M., and Duff, M. P., 2000, A Pipe Manometer for the Determination of Very Small Water-Surface Slopes in the Florida Everglades, Abstract, Greater Everglades Ecosystem Restoration Conference, Naples, FL, December 11-15, 2000.

Lee, J. K., Roig, L. C., and Jenter, H. L., (in review), Flow Resistance in Free Surface Flow through Emergent Vegetation at Low Reynolds Numbers, to be submitted to professional society Journal - December 2000.

Lee, J. K., Roig, L. C., Jenter, H. L., and Visser, H. M., Determination of Resistance Coefficients for Flow through Submersed and Emergent Vegetation in the Florida Everglades, Abstract, Greater Everglades Ecosystem Restoration Conference, Naples, FL, December 11-15, 2000.

Lee, J. K., Ball, M. H. and Duff, M. P., (in preparation), Methods for Flux Calculations from Taylor Slough Velocity Transects, to be submitted as a U.S. Geological Survey Open-File Report - May 2001.

Rybicki, N. B., Reel, J. T., Gammon, P. and Lee, J. K., 1999, Vegetative resistance to flow in South Florida: Summary of vegetation sampling in Taylor Slough, U.S. Geological Survey Open-File Report 99-XXX, YY p.

FY 2000 stakeholder meetings or other outreach activities:

Project personnel participated in the 2000 Florida Bay Science Conference (April), the TIME Modeling Meeting (June) and the Society of Wetland Scientists Meeting (August). In addition, project personnel participated in less formal meetings to discuss findings with colleagues in South Florida.

Bibliography:

Carter, Virginia, Reel, J. T., Lee, J. K., and Rybicki, N. B., 1998, The relation between vegetation and water-flow velocity profiles in an emergent wetland, Everglades National Park, Florida, in Spilhaus, A. F., Jr., ed., Spring Meeting, Boston, 1998, Supplement to Eos, Transactions, American Geophysical Union: Washington, D.C., American Geophysical Union, p. S93 (abstract, poster).

Carter, Virginia, Reel, J. T., Rybicki, N. B., Ruhl, H. A., Gammon, P. T., and Lee, J. K., 1999, Vegetative resistance to flow in South Florida: Summary of vegetation sampling at sites NESRS3 and P33, Shark River Slough, November 1996, U.S. Geological Survey Open-File Report 99-218, 90 p.

Carter, Virginia, Ruhl, H. A., Rybicki, N. B., Reel, J. T., and Gammon, P. T., 1999, Vegetative resistance to flow in South Florida: Summary of vegetation sampling at sites NESRS3 and P33, Shark River Slough, April 1996, U.S. Geological Survey Open-File Report 99-187, 73 p.

Carter, Virginia, Rybicki, N. B., Reel, J. T., Ruhl, H. A., and Lee, J. K., 1999, Vegetative characterization for Everglades studies, in Gerould, Sarah, and Higer, Aaron, eds., U.S. Geological Survey program on the south Florida ecosystem: South Florida Restoration Science Forum, Boca Raton, Fla., 1999, Proceedings: U.S. Geological Survey Open-File Report 99-181, p. 10-11 (extended abstract).

Carter, Virginia, Rybicki, N. B., Reel, J. T., Ruhl, H. A., Stewart, D. W., and Jones, J. W., 1999, Classification of vegetation and characterization of vegetative resistance parameters for surface-water flow models in Taylor Slough, Everglades National Park, in Proceedings Third International Ecohydraulics Symposium, IAHR, Salt Lake City, UT, 14 p.

Jones, J.W., Desmond, G., and Lemeshewsky, G., 1999, "Land characterization for hydrologic modeling in the Everglades", in Proceedings Third International Ecohydraulics Sympo-sium, IAHR, Salt Lake City, UT.

Lee, J. K., 1999, Finite-element surface-water modeling system: Two-dimensional flow in the horizontal plane--Addendum to the users manual: U.S. Geological Survey Open-File Re-port 97-410, 80 p.

Lee, J. K., and Carter, Virginia, 1996, Vegetation affects water movement in the Florida Everglades: U.S. Geological Survey Fact Sheet FS-147-96, 2 p.

Lee, J. K., and Carter, Virginia, 1997, Vegetative resistance to flow in the Florida Everglades, in Gerould, Sarah, and Higer, Aaron, eds., U.S. Geological Survey program on the south Florida ecosystem: Technical Symposium, Ft. Lauderdale, Fla., 1997, Proceedings: U.S. Geological Survey Open-File Report 97-385, p. 49-50 (extended abstract).

Lee, J. K., and Carter, Virginia, 1998, Field measurement of flow resistance due to vegetation in the Florida Everglades, in Spilhaus, A. F., Jr., ed., Spring Meeting, Boston, 1998, Supplement to Eos, Transactions, American Geophysical Union: Washington, D.C., Ameri-can Geophysical Union, p. S87 (abstract).

Lee, J. K., and Carter, Virginia, 1999, Field measurement of flow resistance in the Florida Everglades, in Gerould, Sarah, and Higer, Aaron, eds., U.S. Geological Survey program on the south Florida ecosystem: South Florida Restoration Science Forum, Boca Raton, Fla., 1999, Proceedings: U.S. Geological Survey Open-File Report 99-181, p. 60-61 (extended abstract).

Lee, J. K., Carter, Virginia, and Rybicki, N. B., 1999, Determining flow-resistance coefficients in the Florida Everglades, in Proceedings Third International Ecohydraulics Symposium, IAHR, Salt Lake City, UT, 1999. (Extended abstract).

Lee, J. K., and Guardo, Mariano, 2000, A finite-element surface-water model of Flow-Way Cell 1 of the Everglades Nutrient Removal Project: U.S. Geological Survey Water-Resources Investigations Report 97-4159, 70 p., approved by Director.

Lee, J. K., and Guardo, Mariano, in review. Modeling Surface-Water Flow in a Constructed Wetland submitted to Ecological Engineering.

Lee, J. K., Visser, H. M., Jenter, H. L. and Duff, M. P., 2000, Velocity and Stage Data Collected in a Laboratory Flume for Water-Surface Slope Determination Using a Pipe Manometer, U.S. Geological Survey Open-File Report 00-393.

Reel, J. T., and Lee, J. K., The relation between vegetation and water-flow velocity profiles in a sawgrass marsh, in Gerould, Sarah, and Higer, Aaron, eds., U.S. Geological Survey program on the south Florida ecosystem: Technical Symposium, Ft. Lauderdale, Fla., 1997, Proceedings: U.S. Geological Survey Open-File Report 97-385, p. 74 (abstract).

Rybicki, N. B., Carter, Virginia, Reel, J. T., and Lee, J. K., 1998, The relation between vegetation and water-flow velocity profiles in an emergent wetland, Everglades National Park, Florida, in Annual Meeting, 19th, Anchorage, Alaska, 1998, Proceedings, Society of Wetland Scientists: Anchorage, Alaska, Society of Wetland Scientists, p. 99-100 (abstract).

Rybicki, N. B., Reel, J. T., Ruhl, H. A., Gammon, P. T., Carter, Virginia, and Lee, J. K., 1999, Biomass and vegetative characteristics of sawgrass grown in a tilting flume as part of a study of vegetative resistance to flow, U.S. Geological Survey Open-File Report 99-230, 29 p.

WORK PLAN

FY 2001 activities:

FY 2001 activities will focus principally on completing the vegetative-resistance to flow correla-tion analysis for writing summary reports and journal papers. All requests for FY 2001 funds submitted with this workplan are focused on the production of the identified deliverable journal articles below. The budget request includes funds to support a contract for services of a statisti-cal hydrologist to consult in the analysis of the correlation of vegetation and resistance data using multiple, linear and non-linear, regression techniques, as appropriate, and to assist in the writing of the associated journal articles.

Analysis and documentation of the effects of vegetation on flow structure in the wetlands will be conducted collaboratively by the flow-modeling group (Jenter and Schaffranek) and the vegeta-tion-classification group (Carter and Rybicki). This effort will be largely an in-depth analysis of all synoptic vegetation and flow data collected to date to investigate and describe how vegetation of differing characteristics variously influences flow patterns spatially and vertically in the water column as well as temporally.

Identification and analyses of the dependence and correlation of flow resistance on vegetation characteristics will be focused on developing, through statistical techniques, correlation functions that can then be used to provide improved expressions to treat flow resistance in numerical flow models. The development of empirical relations for representing flow resistance at grid scales consistent with the vegetation characteristics of the Everglades will be determined through a combination of regression analyses, numerical modeling experiments, remote-sensing techniques, and GIS interpretations. This effort is a continuation of collaborative work with John Jones who is funded to do research under the Land Characteristics from Remote Sensing project, but will in-volve a full collaborative effort of both the flow-model and vegetation-classification groups cou-pled with the significant participation of a statistical hydrologist.

FY 2001 deliverables/products:

Journal articles will be prepared on the following topics:

1) Analysis and description of the effects of vegetation on flow structure in the Everglades wetlands.

2) Identification and analyses of the dependence and correlation of flow resistance on vege-tation characteristics.

FY 2001 outreach:

Results will be communicated to the SFWMD, the NPS, the COE, and the public at informal meetings throughout the year. All these agencies will benefit from the use of improved methods for representing vegetative flow resistance in their computer models. The vegetative resistance project has worked closely with Mariano Guardo of the SFWMD in development of the hydrau-lic model of Cell 1 of the ENR Project. Talks and posters will be presented at professional soci-ety meetings as opportunities arise. The project will present results of its investigations at any major interagency stakeholder meetings scheduled during FY 2001.

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