An Dour and the SAGE Léon Trégor are carrying out the vulnerability profile of the coastal waters from the Bay of Morlaix to the Bay of Locquirec, to address microbiological issues. One of the necessary elements to develop is the mathematical modeling of microbiological flows (of bacteria - E. coli, norovirus, and micropollutants) in the coastal areas. The objective is to characterize and prioritize their impacts on pollution flows and their origins based on their types, locations, and modeled events (weather-related, seasonal, or anthropogenic)