Waterborne debris impacts during extreme hydrodynamic events can significantly damage masonry structures. In the current design practice, these forces are commonly characterised by equivalent force-time (F-t) diagrams calculated with analytical models. The US standard ASCE/SEI 7–22 contains a specific model. However, recent studies suggest that the ASCE model may significantly overestimate the load demand and propose an alternative, more accurate analytical model, i.e. the Mass and Stiffness Ratio Model (MSRM). This paper assesses the ASCE design procedure in relation to a potential alternative MSRM application. In doing this, the structural behaviour of a running-bond masonry wall is analysed when subjected to impact loads calculated with the ASCE and MSRM models. The minimum debris design properties by ASCE are used. Various impact scenarios are considered by changing impact locations across the wall. High-fidelity simulations employing micro modelling strategies, nonlinear material models, and strain rate dependent constitutive laws are used. Results show that the ASCE design formulae overestimate maximum structural displacements by over four times, causing disproportionate damage compared to MSRM results. These results highlight the need to revise the ASCE design provision for debris impacts, and the MSRM are recommended as a more efficient alternative to calculate debris impacts F-t diagrams.