The construction of reclaimed islands along the coastline of Dubai with diameters reaching up to 10 kilometres has changed the character and features of the Dubai coastline. The 105-kilometer stretch has no known equivalent in terms of the pace and extent of development shaping up its features into one of the most prized and renowned coast in the world. Inherent to those changes are real and potential impacts that affect among others, water circulation, water quality, shoreline stability, as well as the biological communities in the waters and in the sediments. The impacts need to be well understood, managed and eventually controlled. Mathematical models were developed among other management tools to gain insight of such complex coastal and marine environments. In 2006, local Dubai authorities commissioned HydroQual to develop a three-dimensional numerical model for the purpose of better understanding and predicting the hydrodynamic, water quality and biological processes governing the coast of Dubai. This presentation describes the tool development, application and usefulness to the Dubai authorities involved in managing the continuously evolving coastal and marine environments of Dubai. It also discusses the findings in the context of lessons learned during and after the assessment process, including field deployment, data acquisition and data quality issues. The specifics of the work included conducting an analysis of water quality and other historical available data, Implementing an immediate field program aimed at generating information to support the model calibration, and designing the model grid, set up the three-dimensional, time variable, coupled hydrodynamic/water quality model and conduct final calibration of the model.