Increased infiltration is a key component of Sustainable Urban Drainage systems (SUDs) designed to reduce and delay flood peaks after high-intensity rainfall. However, localized stormwater infiltration may affect groundwater dynamics and water quality. Physically based numerical modelling offers a means to investigate these impacts, though it poses challenges due to differing spatial and temporal resolution requirements for surface and subsurface processes. Analysis of overland (OL) flow, standing water levels and flow directions was modelled with Mike SHE in an area surrounding a swale. The aim is to assess the impact of focused infiltration from a swale in a semi-urban peninsula bordered by a river in Luleå, northern Sweden. The 210 m × 350 m model domain includes a constant-head boundary and two alternative geological profiles, with and without a thin low-permeability layer and topsoil layer. Simulations were performed at 1 m and 2 m spatial resolutions to evaluate effects on overland flow, surface ponding, and groundwater heads during 20-, 40-, and 80- mm rainfall events. Results show only minor differences between the two resolutions in overland flow patterns and the general groundwater heads, whereas geological representation, particularly thin low-permeability layers, had a much stronger influence on system response. For applications not requiring detailed short-term local dynamics, simplified geological conceptualizations may be sufficient.