Wildfire and earth surface processes

Wildfire and post-fire rainfall have resounding effects on hillslope processes and sediment yields of mountainous landscapes. Yet, it remains unclear how fire–flood sequences influence downstream coastal littoral systems. It is timely to examine terrestrial–coastal connections because climate change is increasing the frequency, size, and intensity of wildfires, altering precipitation rates, and accelerating sea-level rise; and these factors can be understood as contrasting accretionary and erosive agents for coastal systems. Here we provide new satellite-derived shoreline measurements of Big Sur, California and show how river sediment discharge significantly influenced shoreline positions during the past several decades. A 2016 wildfire followed by record precipitation increased sediment discharge in the Big Sur River and resulted in almost half of the total river sediment load of the past 50 years (~ 2.2 of ~ 4.8 Mt). Roughly 30% of this river sediment was inferred to be littoral-grade sand and was incorporated into the littoral cell, causing the widest beaches in the 37-year satellite record and spreading downcoast over timescales of years. Hence, the impact of fire–flood events on coastal sediment budgets may be substantial, and these impacts may increase with time considering projected intensification of wildfires and extreme rain events under global warming.

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Biogeomorphic processes, spatial heterogeneity, and river corridor resilience to stand-killing wildfire

Wohl,

Marshall,

Scamardo*

et al. 2024

Biogeomorphic Responses to Wildfire in Fluvial Ecosystems

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We used field-based case studies to examine how spatial heterogeneity influences the response of river corridors to changes in water and sediment fluxes after wildfire. Spatial heterogeneity describes the degree to which a river corridor differs from a spatially uniform feature. Biogeomorphic processes, especially those that involve beaver (Castor canadensis) dams and large wood in the channel and floodplain, both influence and respond to spatial heterogeneity. These feedbacks can in turn strongly influence the degree to which a river corridor is resistant, resilient, or sensitive (RRS) to wildfires. A resistant system experiences little change in process or form following a disturbance. A resilient system absorbs disturbances without diminishing or changing process or form. A sensitive system undergoes persistent change following disturbance. Just as spatial heterogeneity can be characterized with respect to different spatial scales in a river network or river corridor, so different components of a river corridor can vary in their response to disturbance. Consequently, spatial scale and the specific process or landform under consideration will strongly influence designation of RRS. We drew two inferences from the case studies: (1) Reach-scale details of spatial heterogeneity and biogeomorphic feedbacks can be important in determining both reach-scale and network-scale responses to major disturbances such as wildfire, and (2) because of the potential for biogeomorphic feedbacks that either attenuate or exacerbate postfire inputs to river corridors, protecting and fostering reach-scale spatial heterogeneity and the biota involved in biogeomorphic feedbacks can increase river network resilience to wildfire.

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Wildfire and earth surface processes

Cited by 3 publications

References 24 publications

Wildfire activity and impacts on palaeoenvironments during the late Paleozoic Ice Age - New data from the North China Basin

Wildfire activity and impacts on palaeoenvironments during the late Paleozoic Ice Age - New data from the North China Basin

Fire (plus) flood (equals) beach: coastal response to an exceptional river sediment discharge event

Biogeomorphic processes, spatial heterogeneity, and river corridor resilience to stand-killing wildfire

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