Model Calibration and Validation of South Florida Biscayne Bay Coastal Wetlands Watershed

Among the 40 projects in the Florida Comprehensive Everglade Restoration Plan, the Biscayne Bay Coastal Wetlands (BBCW) project has a purpose of re-hydrating wetlands and reducing point source discharge to Biscayne Bay. Seven project alternatives that include rule-controlled coastal canal structures, rule-controlled pump stations, spreader swales, stormwater treatment areas, flowways, levees, culverts, roads, and backfilling canals have been proposed to achieve the purpose. These alternatives are evaluated with the WASH123D model-a first-principle, physics-based numerical model that computes flow and transport in a watershed system that is conceptualized as a combination of 1-D channel network, 2-D overland regimes, and 3- D subsurface media. The WASH123D-BBCW model needs to be calibrated and validated before being used to evaluate the alternatives. This paper presents the calibration and validation of the model. A three-step approach that is used for model calibration and validation is presented, discussed, and evaluated in this paper. The three steps are: calibration of the overland Manning's roughness coefficients (n2) and subsurface hydraulic conductivities (K) with the coupled 2- D/3-D WASH123D-BBCW model where the historical data of canal stage is used as the boundary condition; calibration of the canal Manning's roughness coefficients (n1) where the calibrated n2 and K from the previous step are used; and validation of the calibrated n1, n2, and K with a second set of historical data. The calibration- validation results of the WASH123D-BBCW model are also presented in the paper.