Background: Simulations of fire spread are vital for operational fire management and strategic risk planning.

Aims: To quantify burn heterogeneity effects on post-fire fuel loads, and test whether modifying fuel load estimates based on the fire severity and patchiness of the last fire improves the accuracy of simulations of subsequent fires.

Methods: We (1) measured fine fuels in eucalypt forests in south-eastern Australia following fires of differing severity; (2) modified post-fire fuel accumulation estimates based on our results; and (3) ran different fire simulations for a case-study area which was subject to a planned hazard reduction burn followed by a wildfire shortly thereafter.

Key results: Increasing fire severity resulted in increased reduction in bark fuels. In contrast, surface and elevated fuels were reduced by similar amounts following both low-moderate and high-extreme fire severity. Accounting for burn heterogeneity, and fire severity effects on bark, improved the accuracy of fire spread for a case study fire.

Conclusions: Integration of burn heterogeneity into post-burn fuel load estimates may substantially improve fire behaviour predictions.

Implications: Without accounting for burn heterogeneity, patchy burns of low severity may mean that risk estimations are incorrect. This has implications for evaluating the cost-effectiveness of planned burn programmes.