Changing the Channel: Navigating Toward Self-Mitigation


Changing the Channel:
Navigating Toward Self-Mitigation

Joe Marchianno, PhD candidate, ESSIE, UF
Suzana Arce, JD cadidate, UF Law
Steven Weber, JD cadidate, UF Law
Professor Tom Ankersen, Legal Skills Professor & Legal Program Director, UF Law
Dr. Christine Angelini, Associate Professor, ESSIE, UF

University of Florida Coastal Policy Lab

January 2022

As part of the Fall 2021 Coastal Policy Lab, a partnership between Florida Sea Grant, the University of Florida Conservation Clinic at the Levin College of Law and the Center for Coastal Solutions in the College of Engineering, faculty and students investigated the potential to mitigate the impacts of repetitive maintenance dredging by using more efficient channel designs. The West Coast Inland Navigation District (WCIND) served as the client for this science to policy project, which had two components. The first was to look beyond the traditional “box-cut” template that has often been employed in navigation dredging but may not be the most economically efficient or environmentally sound. Students employed FUNWAVE-TVD modeling software to examine whether sediment accretion can be reduced by varying the depth, width and slope of an idealized channel based on an Intracoastal Waterway channel known as “Intrepid Waters” that is notorious for repetitive dredging in Southwest Florida. 

The second component involved an analysis of State and federal law governing channel dredging, particularly the maintenance dredging exemption. The maintenance exemption serves as a default approach to channel dredging because it often serves as the “path of least regulatory resistance” for cost sensitive and time constrained regional and local agencies charged with maintaining navigation channels. Students concluded that any novel approaches to channel dredging that more than minimally exceed an existing “box-cut” dredge footprint would likely remove a project from the maintenance exemption and require a more costly and time-consuming individual permit. However, the project team also concluded that the environmental “savings” from increasing the interval of time between maintenance operations could potentially offset the one-time environmental impacts of the new dredge footprint, a tradeoff the team termed “self-mitigation.” It was less clear how this approach to mitigation could be applied by the environmental agencies under existing rules and mitigation methodologies. 

In December of 2021, the project team met on site with the WCIND and a representative from Lee County’s Department of Natural Resources to present their results and tour the problematic Intrepid Waters channel. Based on this initial effort and discussions that resulted from the presentation, The Center for Coastal Solutions will continue to process the idealized channel modeling data developed by students in the Coastal Policy Lab and will begin working with WCIND to develop a plan to collect more site-specific field data from the Intrepid Waters channel, allowing more robust, and realistic, modeling from which to eventually field test alternative dredge templates and project the likely frequency of future dredging needed for such templates. Results will enable the CCS and WCIND to determine the extent to which the maintenance dredge interval can be extended, and the extent to which any extended interval might “self-mitigate” the environmental impacts of reduced maintenance dredging, as well as the economic savings over time from a greater one-time investment in an alternative channel deployment.