U.S Geological Survey, South Florida Ecosystem Program: Place-Based Studies

Project: Vegetative Resistance to Flow

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

Location: Central Everglades; Miami-Dade County

Principle Investigators: Harry Jenter, hjenter@usgs.gov, 703.648.5916; Raymond Schaffranek, rws@usgs.gov, 703.6648.5891; Jon Lee (decreased)

Project Personnel: Mike Duff, mpduff@usgs.gov, 703.648.7151; Nancy Rybicki, nrybicki@usgs.gov, 703.648.5728; Justin Reel, jreel@usgs.gov, 703.648.4749; Al Lombana, alombana@usgs.gov, 703 648-4746; Pat Gammon, 757.539.5394

Other Supporting Organizations: Everglades National Park

Associated Projects: Land Characteristics from Remote Sensing (Greg Desmond, John Jones), Tides and Inflows in the Mangrove Ecotone (TIME) Model (Harry Jenter, Ray Schaffranek, Chris Langevin, Eric Swain)

Overview & Status: This project entails various aspects of the study of vegetative resistance to flow in the Everglades of south Florida. Both laboratory and field efforts have focused on the measurement of hydrodynamic and ecological variables used in the calculation of Manning’s n resistance coefficient values appropriate for vegetation types and densities found in the Everglades. Concurrent hydrodynamic and vegetation-characteristic data-collection efforts have been conducted and the current project focus is on processing the entire vegetative-resistance data set collected over previous years to the point where Manning’s n values can be documented and published for use in management models. The vegetation characteristic data have been processed and published previously. A critical aspect of the Manning’s n calculation, the determination of the very small water-surface slopes, is also very near completion. Both the theory and laboratory calibration of a unique pipe manometer device used to measure the small slopes are nearly published. The next phase of the analysis will focus on the correlation of vegetative properties to frictional resistance values. It will also focus on the assignment of resistance values at a spatial scale compatible with surface-water flow modeling efforts in the Everglades.

Needs & Products: This 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?"

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.