Compound Post‐Fire Flood Hazards Considering Infrastructure Sedimentation. Issue 8 (19th August 2022)

• Record Type: Journal Article
• Authors: Jong‐Levinger, Ariane; Banerjee, Tirtha; Houston, Douglas; Sanders, Brett F.
• Is Part Of: Earth's future. Volume 10:Issue 8(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-08-19
• Subjects: compound hazards -- wildfire -- flood -- debris flow -- infrastructure -- Monte Carlo simulation; Environmental sciences -- Periodicals; Environmental sciences; Periodicals; 550
• DOI: 10.1029/2022EF002670
• Languages: English
• ISSNs: 2328-4277

Abstract

Abstract: Flood and debris hazards are heightened following wildfires, but are challenging to quantify due to interdependence between fire frequency and severity, runoff and sediment fluxes during storms, and sedimentation that reduces infrastructure capacity. Herein we present a stochastic simulation framework to estimate compound flood and debris hazards from sequences of wildfires and rainstorms and the accumulation of sediment within flood infrastructure. Application of the framework to a hypothetical watershed representative of southern California shows that the present‐day compound hazard may be up to 6 times greater than the marginal hazard posed by peak flows in the absence of wildfire, and that future compound hazards could be up to 11 times greater than the marginal hazard based on future increases in wildfire frequency. Numerous sensitivities are investigated, including infrastructure design and maintenance, which are shown to be crucial for moderating future increases in post‐fire flood hazards. Plain Language Summary: More frequent and intense wildfires lead to increased risks of flooding and debris hazards following rainstorms. However, existing models for estimating hazards to communities do not account for the filling of protective flood infrastructure with sediment, which reduces capacity. We present an original model for estimating post‐fire flood and debris hazards that captures the interconnected influences of wildfire, rainstorms, and reduced infrastructure capacity from sedimentation. The modeling approach can simulate present and future hazards to aid both short‐term and long‐term risk management efforts. Simulations show that present‐day hazards are up to six times greater based on the interaction of processes compared to flood hazards in the absence of fires. Based on future increases in wildfire frequency, future flood hazards could be up to 11 times greater. Simulations also show that hazards can be reduced with more intensive cleaning and maintenance. Key Points: Post‐fire flooding represents a compound hazard based on interdependence between fire, runoff, and infrastructure sedimentation A new modeling framework is formulated and applied to simulate compound post‐fire flood hazards using stochastic inputs Compound post‐fire flood hazards can be up to an order of magnitude greater than flood hazards in the absence of fire