Analysis of Bridge Construction as a Restoration Technique for Everglades National Park, FL, USA, Using Hydrological Numerical Modeling

Abstract

Since the construction of the Tamiami Trail in the 1920s, overland flow to the Florida Everglades has decreased significantly, affecting ecosystems from the wetlands to the estuary. As part of the effort to return flows to historical levels, several changes to the existing water management infrastructure have been implemented or are in the design phase. These changes include the construction of two bridges [a 1.6-km (1-mi) and a 4.2-km (2.6-mi) bridge] and the removal of the Tamiami Trail roadway, as well as increasing canal water levels to increase head elevations north of Everglades National Park (ENP). A numerical model of ENP hydrology was developed using MIKE SHE/MIKE 11 software to review the effects of these structure changes and evaluate the potential impact of bridge construction. Model simulations show that the newly constructed 1.6-km bridge along the Tamiami Trail could increase water delivery to the Northeast Shark Slough (NESS) by about 6%. The 1.6-km bridge, plus the proposed 4.2-km bridge, could increase flows by about 10% from the baseline. These simulations also show an increase of flow to the eastern canals by less than 1% for each scenario, demonstrating that bridge implementation along the Tamiami Trail will have a minimal impact on eastern canal operations and flood management. The percent probability of water levels exceeding baseline conditions was determined for the simulation period. This analysis showed that the length of time of inundation, or the hydroperiod, would increase for large areas of the park with the introduction of each bridge. Additional simulations were conducted to demonstrate the effect of proposed water-level increases for canals north of the park. Raising water levels in the canal by up to 0.3 m (1 ft) increased overland water levels up to 21 cm in some areas within ENP. These simulations demonstrate that a general increase in water levels and hydroperiods within ENP will be achieved by adding bridges to the Tamiami Trail roadway and by increasing water levels in the canal.