Establishing appropriate boundary conditions is essential for developing high-accuracy hydrodynamic models. However, this task is particularly challenging in topographically varying urban domains without monotonous slopes due to insufficient boundary information. This study investigates five different boundary conditions and establishes modeling practices of boundary conditions in pluvial urban flood modeling. A numerical test model within the city of Berlin is used, employing the 2D hydrodynamic finite element module of the open-source TELEMAC system. It performs unsteady simulations with nodal rainfall inputs for various precipitation scenarios, excluding infiltration. The results demonstrate that the suitability of boundary conditions is critically dependent on the surrounding topography. For boundary segments with a positive slope, a stage–discharge curve is found to outperform the other boundary conditions investigated in this study. Conversely, for segments with a negative slope, a closed wall boundary condition appears clearly preferable. Additionally, a drainage reservoir boundary condition performs effectively for more complex boundary segments but necessitates extensive preprocessing. Based on these insights, simulations were repeated with segment-tailored boundary conditions. The results indicate that this combined model outperforms the global application of each individual model.

According to the latest IPCC report, climate change directly impacts the intensity and frequency of floods in urban areas. As a result, Flash floods, characterized by a rapid increase in flood peak during a short duration, are becoming more common. Managing these flash floods is a crucial yet challenging task for water authorities. One important tool supporting the management of flash floods are 2-D hydrodynamic models.In this study, we use the 2-D module of the openTELEMAC-MASCARET software to investigate the effect of the building representation on an urban flash flood. For this, we isolate a sinuous-shaped building group within an artificial study area. The building group itself and the topography in the model are derived from the Moabit district in Berlin. The buildings are cut out from the model as a hole, and the impact on the model results from the vertex distribution around these holes is assessed. We compare different algorithms to resample the vertices of the building. First, we design an algorithm that resamples the vertices of the building edges at an even distance while conserving the overall shape of the building. The resampling distance is set globally but slightly varies for every building edge. This algorithm is then compared with built-in resampling tools from other software: one tool also conserves the shape of the building yet cannot resample the vertices at an even distance (from QGIS), and another tool resamples at an even distance, yet does not conserve the building shape (from SMS). A change in the distribution of vertices causes a change in the mesh distribution around the buildings. Hence, the flow pattern around the buildings also changes. Additionally, we study the numerical stability of the different distributions. With this study, we aim to deepen the understanding of building representation in urban flood modeling and set the path for further investigations within this topic.

Accurate simulation of flood dynamics in urban environments requires resolving complex flow patterns generated by buildings, yet fully high-resolution meshes still remain computationally too expensive. This study evaluates the potential of local mesh refinements to improve urban flood modeling while maintaining a reasonable computational cost. Using the well-established Toce Experiment as a benchmark, two local refinement strategies, edge refinements along building edges and areal refinements extending into the surrounding flow field, are implemented within the TELEMAC-2D framework. The results show that each of these local refinements improves the simulation accuracy of water depths and more substantially enhances the reproduction of fine-scale velocity structures around buildings, which coarse meshes fail to capture. Areal refinements provide the most consistent improvements in the predicted flow patterns, while edge refinements may be more applicable in complex urban study areas due to limited preprocessing requirements. A detailed analysis of the Toce Experiment also highlights the sensitivity of numerical predictions to inlet conditions and roughness parameters, revealing hidden uncertainties within the benchmark dataset itself. These findings demonstrate both the benefits and the practical limitations of local mesh refinements in 2D urban flood modeling, providing guidance for developing computationally efficient yet physically robust hazard simulations.

Net radiation (Rn) is a key control on land–atmosphere exchanges and a primary forcing for transpiration modelling. However, commonly used radiation products often lack the spatial resolution required to resolve soil–plant–atmosphere interactions in heterogeneous landscapes, limiting their applicability for water management studies. Here, we present a new daily net shortwave and net radiation dataset for Europe at 1-arcminute (~1.4 km) spatial resolution covering the period 2001–2020, developed to support high-resolution transpiration modelling using the Priestley–Taylor approach.The dataset is generated through the integration of multiple complementary data sources, combining station-based downward shortwave radiation from the EMO-1 dataset, satellite-derived longwave radiation from the ELITE product, and a physically based estimation of blue-sky albedo derived from GLASS black and white-sky albedo products, together with information on photosynthetically active radiation from BESS.Evaluation against FLUXNET observations reveals that the high-resolution net shortwave radiation product outperforms the coarser ERA5-Land reanalysis across 7 of 9 analyzed European countries, with particularly strong improvements in topographically complex regions, such as the Alps, and in heterogeneous land-use areas. However, the net radiation product shows larger uncertainties in semi-arid regions and during high-latitude winter conditions, reflecting known limitations in satellite-based radiation retrievals. Nevertheless, the high spatial resolution represents a valuable contribution to remote-sensing-based water cycle studies, drought assessment, and land-surface modeling.