In the federally approved Comprehensive Everglades Restoration Plan (CERP, http://www.evergladesplan.org/), the restoration of the South Florida ecosystem is a major task for the U.S. Army Corps of Engineers and the South Florida Water Management District. Many competing entities have an interest in the restoration process which will probably include physical changes to the land surface and adjustments to water deliveries. The Biscayne Bay Coastal Wetlands (BBCW) Project is one component of more than 60 restoration plans and has a goal to restore or enhance freshwater wetlands, tidal wetlands, and near shore bay habitat. In an effort to restore wetlands, several structures, and management plans and scenarios are considered. One of the plans is to deliver fresh water from the existing canals through a shallow spreader canal system that is to distribute fresh water through wetlands into the Biscayne Bay. To achieve this, a tool is needed to design this complicated shallow spreader canal system. This paper presents how a spreader canal system, which includes ID canal network routing, 2D overland flow, 3D subsurface flow, and flow through the interface of any two sub-domains of the spreader canal system, is simulated with the WASH123D computer code. A brief description of the model will be given. A hypothetical example that includes two cases and uses topographic data and a high-resolution computational mesh for one project area will be considered to demonstrate how WASH123D can help design a spreader canal system. A couple of issues concerning run time and numerical convergence of the coupled flow model will also be discussed in this paper.