The surprising power of fragmentation: How fuel discontinuity limits wildfire spread
Date
2025
Authors
Bitz, Quinn
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Abstract
Wildfire growth depends not only on the quantity of fuel but also on its continuity across the landscape (Keane et al., 2001; Pfeiffer et al., 2013). Fine-scale discontinuities such as roads, rivers, or rocky outcrops can halt fire progression, yet these features are often overlooked in large-scale fire models that treat fuels as homogeneous (Archibald et al., 2009; Bowman et al., 2020). This project investigates how fuel fragmentation at 30 m resolution constrains burned area in realistic landscapes.
Using the ELMFIRE fire spread model (Lautenberger, 2013) with LANDFIRE LF 2023 inputs (LANDFIRE, n.d.), I simulated nearly 8,000 ignition scenarios across five 60 × 60 km domains in the western United States. Burned and burnable area fractions were calculated for each 5 × 5 km tile (sub-domain) to quantify how fuel discontinuities interact with wind and landscape structure.
Results show that burned area increased exponentially across the full range of fuel continuity, forming an upper-limit relationship between burnable and burned area fractions. Fragmented landscapes rarely supported large-scale spread, defined here as cases where more than half of the burnable area was consumed. Wind speed had little effect under low connectivity, but in continuous fuels, stronger winds substantially amplified fire size. Other potential controls, including slope and vegetation structure, were weakly related to burned area, reinforcing fragmentation as the dominant limiting factor.
These findings demonstrate that fuel continuity imposes natural limits on wildfire growth, even under favourable weather. Incorporating such constraints into continental- and global-scale fire models could improve their ability to capture realistic spread dynamics in heterogeneous landscapes.
Supervisors: Jed O. Kaplan and Colin Goldblatt
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Keywords
wildfire, fuel discontinuity, fire spread modelling, landscape fragmentation, LandFire, ELMFIRE