The National Weather Service uses its 1-dimensional generalized flood wave routing (FLDWAV) model, which has the ability to account for the effects of tidal conditions and storm surges in coastal rivers, to forecast the water surface elevations and discharges in the St. Johns River, FL. However, there is a transition area between the river and the coast (in the estuary) where a one-dimensional model may not be adequate because the assumption of a horizontal water surface may not be valid. The National Ocean Service uses the 3-dimensional Environmental Fluid Dynamics Code (EFDC) model to simulate the hydrodynamic circulation in the St. Johns River and estuary. As part of the Coastal Storms Initiative, a comparison of the modeling results between FLDWAV and EFDC is done to determine the limitations of 1-dimensional modeling in coastal rivers and to improve the river forecast in the transition area. A combined flood forecast map representing both the river and coastal components is also being developed. A comparison of the two model results in the common area will be presented and the development of an integrated flood forecast map is also discussed.