Numerical investigation of the effectiveness of shaded fuel break prescriptions for WUI fire scenarios

Shaded fuel breaks are intended to provide suppression opportunities for the emergency services and they are currently also being considered as mitigation strategies for the protection of assets located at the WUI. The prescriptive characteristics of these fuel breaks depend on regional regulations, which often differ. In this manuscript, the effectiveness of shaded fuel break regulations of the neighbouring regions of Catalonia (Spain) and Pyrénées-Orientales (France) is quantitatively analysed and compared through FDS (Fire Dynamics Simulator) simulations. The vegetation within the fuel break, simulated in form of Lagrangian particles, is exposed to a predefined wildland fire with two different fireline intensities (10000 kW/m and 30000 kW/m) and two wind speeds (15 km/h and 28 km/h). An untreated scenario is also analysed. Results show that the analysed fuel break prescriptions reduce fire behaviour metrics to values that allow for safe intervention for suppression from the emergency services. However, when it comes to asset protection when emergency services are not able to intervene, a width of 25 m (minimum width prescribed in Catalonia) is not sufficient in cases with high winds or high fireline intensities, while a width of 50 m (in Pyrénées-Orientales) is also insufficient when exposed to high winds.