Macro Scale Wetlands Restoration by Drainage Canal Removal—Challenges, Solutions, and Lessons Learned.

This paper describes some of the findings and outcomes of a nationally prominent wetlands restoration program which is unusual in scale (55,000 acres) and hydraulic complexity. Ecosystems prevailing in the area of the Picayune Strand Restoration Project (PSRP) in southwest Florida had been profoundly impacted by the installation of drainage canals designed to lower water tables on a regional scale and thereby create large tracts of developable land. This development effort had eliminated the original mix of natural overland flow and amorphous flowways, replacing it with a highly structured network of canals, roads and associated ditches or other hydraulic features. Present plans are to recover the natural condition by eliminating the canal system over an area of some 55,000 acres. A constraint to these plans was thateighboring areas, including agriculture, residential, business, transportation and natural systems areas, were not to be adversely impacted. In particular, backwater flooding of upstream developed areas which might result from canal removal downstream was to be avoided. A substantial design analysis was performed to establish how best to maintain some form of positive drainage in a way that does not increase the potential for flooding outside the project area. It was decided that upstream flows would be captured and discharged through several large (several thousand cfs) pumps to lateral spreading canals that approximate predeveloped overland flow conditions. The design options to accomplish this basic scheme were numerous and involved a variety of candidate configurations. Ultimately, plugging the original canals at intervals was found to be hydraulically efficient and cost effective compared to total filling. In the long term, natural process will complete the process of infilling the canal drainage network. This paper discusses the analyses that were undertaken to establish the preferred restoration plan, the results of the project in its present partially complete state, comparisons of measured groundwater responses in the pilot restoration area to simulated responses and lessons learned as construction and monitoring has been pursued. In particular, the concerns raised by observed plugging practices are noted, and lessons learned for this type of large scale rehabilitation are provided. Suggestions are made regarding preferred practice, and areas meriting further research are identified.