Strategies for modelling roofs on large-scale urban drainage models focusing on incomplete data scenarios

Impermeable surfaces such as roofs play a key role in urban pluvial floods due to the rapid transfer of rainfall to drainage networks, contributing to system overloading. This study proposes and evaluates different modelling strategies within large-scale urban drainage models, exploring simplified approaches for roof geometry and roof-to-manhole connections. The results indicate that, regardless of the methodology used to estimate roof width, the differences become negligible if the discharge point is distant. Additionally, for a contributing area of roofs discharging upstream to a manhole, the method of roof-to-manhole connection does not have a significant influence, which demonstrates the potential of these strategies to streamline the modelling process without compromising the reliability of the simulations. The findings highlight the feasibility of applying these modelling strategies in situations where data completeness is not feasible, offering a balanced solution between model complexity and accuracy. • Roof geometry modelling strategies allow estimating width without compromising the accuracy of simulated roof discharges. • Assigning roofs to the nearest manhole based on proximity yields reliable results in connection modelling strategies. • Virtual roofs formed through block aggregation can replace actual roofs without compromising the accuracy of the model. • These modelling strategies can be used in incomplete data scenarios when roof geometry and connections are missing • The study offers a practical method to simplify model setup, crucial for large urban applications.