It is good modelling practice to parameterise your model specific to the location and conditions you are modelling. Paramaterisation of a model includes the selecting the correct rainfall data, defining the catchment and ensure that the pollutant characteristics are representative of your catchment. MUSIC provide default parameters which in some cases will be appropriate though in all cases it is recommended they are reviewed and changed as needed.
Generally you should adjust pollutant loadings to differentiate between roofs and ground level impervious surfaces. It is recommended that you seek guidance from your local authority or regulator to ensure you are setting up your model according to their requirements.
Refer to Australian Runoff Quality - A guide to Water Sensitive Urban Design for general guidance on pollutants by land use category or Urban Stormwater Quality: A Statistical Overview (Hugh Duncan - CRC for Catchment Hydrology)
Additional resources include: