Cooperative Ecosystem Studies Unit, South Florida-Caribbean CESU

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The Everglades Depth Estimation Network (EDEN) provides a critical dataset that supports biological models of the Everglades ecosystem for the Comprehensive Everglades Restoration Plan (Telis, 2006). Development of EDEN is an iterative process as additional high accuracy elevation data are collected, water surfacing algorithms improve, and additional ground-based ancillary data become available (Jones and Price, 2007). Data from EDEN are being actively utilized by different research groups and the feedback from them are essential for evaluating and improving EDEN. Recently, the Gawlik Lab at FAU found that the computed hydroperiods from EDEN data are more variable and patchy in WCA1 (A.R.M. Loxahatchee National Wildlife Refuge) than other sub-regions (Figure 1), seemingly reflecting fine scale topographic variation from the many small tree islands in WCA1. To assess whether the hydroperiod and water depth differences are the result of elevation changes in the digital elevation model (DEM), the EDEN DEM and DOQQs (1-m, 2004) were overlaid and examined. It was noticed that some cells in WCA1 did have DEM values as much as 30 cm greater than the surrounding cells, while no obvious difference in landscape patterns were shown (Figure 2). It was suspected that elevations for such cells might be measured on small tree islands or other higher ground, and the interpolation process (to create the DEM) did not smooth out these measurements as it did in other sub-regions with larger tree islands prevalent (Figure 3). Further investigation confirmed that different rules were applied when interpolating the DEM in WCA1 (Telis and Higer, USGS, personal communication). The high variability in fine scale topography in WCA1 poses special problems for the interpolation of the DEM, because it is not clear how much of that variability should be smoothed to match the DEM in other areas and how much should be preserved, and thus reflect the unique character of WCA1. To provide a solid foundation for subsequent analyses of EDEN data, it will be necessary to quantify the patterns of variability and error in the DEM within WCA1. The success of the proposed research will help refine the EDEN dataset and greatly benefit the research and management activities in WCA1. The research included in this agreement is designed to answer questions critical to restoration success. There are three related research Objectives that are contained within the current cooperative program: Objective 1 – This Objective will develop a reference base of ground elevation data and other information, primarily for WCA1. Objective 2 – This Objective will develop a statistical comparison of modeled EDEN DEM to measured ground elevations. Objective 3 – This Objective will document a SAS program for batch processing of EDEN surfaces.

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