Project Summary Sheet

Project: Vegetative Resistance to Flow

Web Sites: http://sofia.usgs.gov

Location (Subregions & Counties): Central Everglades; Miami-Dade County

Funding (Source): Not funded in FY2002. Previous funding from USGS Greater Everglades Science Program: Place-Based Studies and the Critical Ecosystem Studies Initiative (administered by the NPS)

Principal Investigator(s): Harry L. Jenter (703 648-5916, hjenter@usgs.gov )

Project Personnel: Michael Duff (703 648-7151, mpduff@usgs.gov ); Nancy Rybicki (703 648-5728, nrybicki@usgs.gov ) ; Al Lombana (703 648-4746, alombana@usgs.gov ) ; Pat Gammon (757 539-5394)

Supporting Organizations: Everglades National Park

Associated / Linked Projects: Land Characteristics from Remote Sensing (Greg Desmond, John Jones), Tides and Inflows in the Mangroves of the Everglades (Harry Jenter, Ray Schaffranek, Christian Langevin, Eric Swain)

Overview & Status: This project entails the study of vegetative resistance to flow in the Everglades of South Florida. Both laboratory and field efforts have been focused on collection and analysis of hydrodynamic and vegetation-characteristic data used in the calculation of Manning’s n resistance coefficients appropriate for vegetation types and densities found in the Everglades. The ultimate goal of this work is determination of representative Manning’s n values for the use in management models. The primary finding of the project to date is the quantification of vegetative resistance as a function of Reynolds’ Number with a length scale based on the spacing between plant stems. In addition, the correlation between plant stem spacing and other vegetation-characteristic data has been assessed and will be used to explore the critical link between the Stem Reynolds Number and remote sensing data. This project began in 1995 under the direction of Jon Lee, who passed away unexpectedly in December, 1999. It was then placed briefly under the direction of Ray Schaffranek and Harry Jenter, and then exclusively under the direction of Harry Jenter. Project funding was not requested in FY2002.

Needs & Products: The project aims to answer the following questions: 1) "What is the valid range of values for Manning’s n within the Everglades ecosystem?" 2) "What vegetation characteristics correlate best with Manning’s n values computed from measured sets of flow data?" 3) "Can Manning’s n values be assigned meaningfully at scales compatible with numerical flow models of the Everglades ecosystem at regional levels?" 4) "Would other frictional resistance formulations, rather than Manning’s n, better represent vegetative resistance in flow models?" A peer-reviewed journal article describing the correlation between frictional resistance and Stem Reynolds Number has received USGS Director’s Approval and has been submitted to the ASCE Journal of Hydraulic Engineering. A manuscript describing the correlation between Stem Reynolds Number and other vegetation characteristics, which may be remotely-sensed more easily is in preparation. Results from this study are being incorporated into the surface-water flow model of the Tides and Inflows in the Mangroves of the Everglades (TIME) project.

Application to Everglades Restoration: This project addresses a critical need of surface-water flow modeling in South Florida. Without an understanding of frictional resistance caused by vegetation, numerical flow models have limited confidence in reproducing the correct flow patterns in such a highly frictional environment.