12.15 Fire as a Geomorphic Agent

Abstract

Intense heat produced by fire and the burning of vegetation can significantly alter geomorphic features and processes. The effects of fire on geomorphology include increased erosion, runoff, and weathering rates, and changes to soil properties and hydrologic processes. Fire severity and extent commonly determine fire's influence on geomorphology. Widespread, high-severity fires may alter sediment loads, erosion rates, and streamflow for an entire drainage basin; however, small, low-intensity fires may not produce any noticeable geomorphic changes. Location and environmental conditions also exert strong influence on the degree of fire's effects. Vegetation type and density, topographic features, and soil conditions may buffer, enhance, or influence the pattern of geomorphic disturbance. Many geomorphic alterations are a result of loss of vegetation, and the duration of the changes to geomorphic processes is generally related to the re-establishment of vegetation. Inversely, damage to geomorphology may influence vegetation regrowth rates, pattern, and composition. The effects of fire on geomorphology are well addressed in the literature, particularly for fire-prone regions and for common and highly visible geomorphic changes. This chapter provides an overview and a synthesis of major topics of fire–geomorphology interactions as they are presented in the literature. Topics addressed include soil hydrophobicity, infiltration, mineralization, and nutrients; surface erosion and mass movements; weathering; runoff, streamflow, and morphology; prehistorical fire and geomorphology; and topographic influence on fire behavior.