The impact of hydrological model resolution on streamflow estimation and catastrophe model event clustering

Hydrological models are essential tools for generating streamflow estimates across various scales. While the choice of model structure is often scrutinized, the spatial resolution at which these models operate is a critical factor that directly influences the accuracy and representation of hydrological processes (Hoch et al., 2023; van Jaarsveld et al., 2025):  coarser resolutions may fail to capture localized runoff dynamics, whereas finer scales offer better precision at the cost of computational intensity.

One application of hydrological models is to identify and group discharge peaks into event catalogues. These catalogues are integral components of catastrophe (CAT) models, used by the insurance and disaster-management sectors to quantify their portfolio risk and guide underwriting.  However, the spatial resolution of the underlying hydrological model may introduce uncertainty into this process: discrepancies in streamflow timing and magnitude resulting from resolution choices may alter how events are clustered, potentially leading to variations in the frequency and severity of events recorded in an event catalogue.

This study presents a sensitivity analysis evaluating the impact of varying model resolutions of the hydrological model Wflow on both streamflow estimations and the subsequent generation of event catalogues. By comparing model outputs across multiple spatial resolutions in the UK and Ireland, we assess the degree of (dis-)agreement in event identification and clustering. Our results aim to shed light on how spatial discretization choices propagate through the risk-modelling chain, ultimately affecting the reliability of flood impact assessments and financial risk projections.

 

Hoch, J. M., Sutanudjaja, E. H., Wanders, N., Van Beek, R. L. P. H., and Bierkens, M. F. P.: Hyper-resolution PCR-GLOBWB: opportunities and challenges from refining model spatial resolution to 1 km over the European continent, Hydrol. Earth Syst. Sci., 27, 1383–1401, https://doi.org/10.5194/hess-27-1383-2023, 2023.

van Jaarsveld, B., Wanders, N., Sutanudjaja, E. H., Hoch, J., Droppers, B., Janzing, J., van Beek, R. L. P. H., and Bierkens, M. F. P.: A first attempt to model global hydrology at hyper-resolution, Earth Syst. Dynam., 16, 29–54, https://doi.org/10.5194/esd-16-29-2025, 2025