Coupling sewers to the surface: Systematic approaches to correcting data discrepancies for 1D-2D drainage modelling

• 1D–2D pluvial flood models require matching 1D sewer elevation and 2D DEM data. • Two methods to automatically remove common data discrepancies are proposed. • Method 1 corrects the 1D domain, while minimising changes to the sewer system. • Method 2 edits the DEM, while minimising changes to the catchment topography. • The impact of the adjustments is evaluated using hydraulic or hydrological simulations. One-dimensional (1D) drainage models coupled with two-dimensional (2D) surface models have been recognised as most suitable for simulating pluvial floods in urban areas. However, discrepancies between the 1D drainage network and the 2D Digital Terrain Model (DTM) surface elevation datasets are often observed. These incompatibilities are commonly adjusted manually, impacting the transparency and reproducibility of flood modelling results. No automated and reproducible methods are currently available to ensure compatibility and consistency between a 1D drainage network and the 2D DTM elevation dataset. We present two methods for automatically correcting these discrepancies: Method 1, which corrects the discrepancies by editing the 1D drainage network, and Method 2, which corrects the discrepancies by editing the elevation of the 2D surface. Both methods ensure 1D–2D data compatibility. The two methods were evaluated through hydraulic and hydrological simulations using a synthetic case study, demonstrating strong performance for both approaches. Additionally, we propose a procedure to guide practitioners and modellers in discerning between 1D data and 2D data errors and choosing which method to use. This procedure is demonstrated for a real case study. The two presented methodologies can improve the process of creating 1D-2D urban drainage models and their reproducibility.