research question for modelling extreme rainfall event with coupled 2D surface and 1D sewersystem model
It sounds as though you have ideas on the tools you'd like to use, but not on an actual question that you want to use them to answer.

You probably need to either come up with such a question, or focus instead on methodology - in studying the tools and the effectiveness of using them in a given scenario.

For nearly any modelling project, its viability will be affected by whether data are available to validate the model. If no appropriate data are available for the area you're looking at, you probably don't have a project (because what use is a model if you have no idea whether it's right?).

Bear in mind that these comments are all generalisations based on very limited information. The best advice is still "talk to your advisor".