POST-FIRE EROSION: RE-VISIONING SCIENCE, CONTEXT, AND CONSEQUENCES

Over the past decades the science of post-fire hydrology and erosion focused primarily on how changes to soil properties fostered enhanced runoff and erosion and addressed threat assessments as local surface hydrology problems, specifically flooding and debris-laden flows, limited to low order catchments. We argue that advances in post-fire response require a re-visioning of core fire hydrology science, evaluation of hydrogeomorphic response across wider geographic and temporal domains, and considering future post-fire response in the context of shifting climate drivers and increasing human population. We urge abandoning the false dichotomy of soils versus vegetation effects and instead focusing on the interaction of first-order controls within an integrated biogeophysical and spatial framework. The geographic extent of flood and sediment pulses extends downstream beyond initial threat zones and interact across scales with other disturbance processes. Consequences to ecosystem health and human use may vary in time with variable signal strength. Direct fire effects interact with rainfall and snow hydrology and alter near surface flow and groundwater recharge processes. Shifting climate drivers and growing population pressure are expected to increase the frequency, spatial extent, and severity of future wildland fires. Increases in severely burned area coupled with possible increases in rainfall magnitude and intensity may amplify the consequences of post-fire response. At some threshold of land area burned and interaction with insect infestation and infectious disease the response of bio-hydrogeomorphic systems may shift states. Disturbance signals may emerge, amplify, and propagate further downstream and into groundwater systems. We present conceptual models and discuss research implications of re-envisioned approaches to the science of post-fire hydrogeomorphic response, broad-scale views of the effects within hydrologically connected systems, and possible trajectories under altered climate regimes and population growth.