ISSUE DEFINITION

Many South Florida stakeholders from government, private industry, environmental, and citizen sectors are collaborating in an effort to return the Florida Everglades system to its ìnatural stateî in terms of restoring its values and functions as an integrated wetland system. Research into the measurement and modeling of water movement and other hydrologic processes is a primary scientific need in support of Everglades restoration. To accurately simulate surface water hydrology in South Florida, scientists must determine the variation in vegetation cover and the role vegetation plays in removal of surface water, resistance to surface water flow, and water quality. The objective of this research is to develop and apply innovative remote sensing and geographic information system techniques to characterize and map the distribution of vegetation and related hydrologic variables, such as evapotranspiration, through space and over time. This work will provide insights regarding the role South Florida vegetation plays in the redistribution of rainfall and surface flow inputs as well as the cycling of nutrients and other materials in the Everglades waters. It will contribute to our understanding of hydrology at large scales. Finally, it will lay the foundation for monitoring the effects of restoration on Everglades flora. These benefits are vital in building the understanding required to properly monitor, simulate, and manage the unique Everglades wetland resource.

BACKGROUND

The extrapolation of processes typically measured or modeled at point locations or at microscales to macroscales is an extremely difficult undertaking. However, this capability is needed to identify the important components of the natural system, quantify the impacts of human activity on the system, forecast system behavior, and monitor the effects of restoration actions. This work will develop the techniques and produce the data sets necessary to conduct hydrological modeling (surface water flow and water budget) at the regional scale. Additionally, success in developing periphyton mapping techniques would produce a critical new tool for biogeochemical and water quality research.

In situ and remotely sensed data from numerous platforms and sensors, each possessing different spatial, temporal, and spectral resolution, will be processed, analyzed, and combined to produce information about biophysical variables (for example, vegetation species composition, vegetation density, vegetation structure, and components of the surface energy balance), as well as image maps of South Florida. These data will be evaluated for their utility in specific modeling and monitoring contexts. Image map products will be developed to convey the results of this work and to portray current vegetation conditions in South Florida to the broadest audience possible.

STATUS/PROGRESS TO DATE

The overall task has been divided into four primary components with specific objectives and general classes of clients. Component one concerns the regional extrapolation of point evapotranspiration measurements and the role of vegetation in surface-water evaporation. Component two is aimed at vegetation-density mapping for resistance to flow modeling. Component three is a pilot study of periphyton mapping techniques using hyperspectral remote sensing capabilities. The fourth component is the development of new, large scale image maps of the Southern and Inland Coastal System model study area within the Everglades National Park.

For each component, the U.S. Geological Survey (USGS) is systematically developing, evaluating, and applying the techniques that yield the most appropriate, spatially distributed information possible on the vegetation, climate, and hydrologic variables of interest to South Florida project scientists. For example, the Priestly-Taylor method is being evaluated as a means of estimating Everglades evapotranspiration without the need for extensive and costly data collection (see German, this volume). This method has been modified to use remotely sensed inputs of leaf area index (LAI) in environments quite different from South Florida. Although it is not yet clear whether LAI can be accurately measured for all dominant vegetation types in the Everglades environment using remote sensing, we have detected a strong relationship between sawgrass biomass and high spatial resolution remotely sensed indexes. Such analysis is possible given the combination of field campaigns (to provide ground truth information for data calibration and accuracy assessment) and extensive technique development that we are applying in each project component.

Remote sensing data from multiple sensors of differing spatial and spectral resolutions have been collected and are being processed. New image data fusion tools that maximize information content to support the interpretation of biophysical fields and yield improved image maps have been developed. To improve machine techniques for vegetation density mapping, scientists developed a new, artificial neural network technique that increases the spatial resolution of thermal-infrared imagery. Collaborative use of the resulting products will allow the evaluation of their utility for process modeling and environmental monitoring while facilitating outreach and technology transfer.

FUTURE EFFORTS

Since the capability to map LAI would contribute to widespread use of the Priestly-Taylor method and perhaps to the vegetation density mapping component, development of LAI estimation techniques at multiple scales using remote sensing will be an important research thrust in the near future. Information products and techniques developed through this project will be transferred to other scientists and management agencies by means of technical reports, existing program public information outlets, and other professional publications and meetings. Selected information produced through this effort (for example, satellite image maps) will be reproduced in sufficient quantity to allow wide distribution to both specialized users and the general public, thus providing increased understanding of the region and the role of the USGS in addressing scientific and management needs. Examples of upcoming major products are hard-copy maps, digital database layers of vegetation and hydrologic variables, CD-ROM's of derived information, and knowledge regarding the scaling properties of various surface features and processes.

(This abstract was taken from the Proceedings of the South Florida Restoration Science Forum Open File Report)