STREAM RESTORATION PROJECTS
Jonathan Dickinson State Park (JDSP), Northwest Fork Loxahatchee River Floodplain Hydrologic Restoration, Hobe Sound, Florida
Problem: The project site is located along the southeast bank of the Wild and Scenic Northwest Fork Loxahatchee River at a location just north of Indiantown Road (SR706), and west of the Florida Turnpike/I-95 corridor within the boundaries of the Jonathan Dickinson State Park (JDSP). The river at this location was impacted in the past by agricultural cross ditching and pumping of groundwater to maintain water levels for crops. Recreation use and resource management, and the River suffers from a reduced hydrologic base flow along the river floodplain and surrounding depleted wetlands. Backfilling of three ditches at the site will be of substantial benefit to impacted individual wetlands for restoration of more natural hydro period along the river’s floodplain.
Solution: A field horizontal and vertical control survey of the project site area was performed in early November 2003. The field survey included approximately one mile of total ditch cross sections, typical sections at approximately 100 feet intervals, and spot elevations of the area between ditches on a 500-feet grid. The field cross sectional survey data was applied for the preparation of engineering construction drawings to be used in the proposed filling of drainage ditches. Imagery for the site was available in the form of black and white historical photos from the United States Geological Survey (USGS), and color infrared (CIR) digital ortho quads (DOQ’s) from the South Florida Water Management District. A 1940 B/W photo that was scanned at high resolution, geo-rectified, and overlaid with other planimetric data using GIS for hydrologic assessment. Historical flow and stage data of the nearby Lainhart Dam was acquired to assess flow regimes near the study area. Historical vegetation boundary analyses show that the three ditches proposed for backfilling are located within the historical connections to riverine wetlands. This indicates the need to re-establish the flow exchange that took place between the riverine wetlands and these “upland” connections.
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