The evolution of a colluvial hollow to a fluvial channel with periodic steps following two transformational disturbances: A wildfire and a historic flood
Geomorphology
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Abstract
The transition of a colluvial hollow to a fluvial channel with discrete steps was observed after two landscape-scale disturbances. The first disturbance, a high-severity wildfire, changed the catchment hydrology to favor overland flow, which incised a colluvial hollow, creating a channel in the same location. This incised channel became armored with cobbles and boulders following repeated post-wildfire overland flow events. Three years after the fire, a record rainstorm produced regional flooding and generated sufficient fluvial erosion and sorting to produce a fluvial channel with periodically spaced steps. An analysis of the step spacing shows that after the flood, newly formed steps retained a similar spacing to the topographic roughness spacing in the original colluvial hollow (prior to channelization). This suggests that despite a distinct change in channel form roughness and bedform morphology, the endogenous roughness periodicity was conserved. Variations in sediment erodibility helped to create the emergent steps as the largest particles ( >D84) remained immobile, becoming step features, and downstream soil was easily winnowed away.
Suggested Citation
Rengers, F.K., McGuire, L., Ebel, B.A., and Tucker, G.E., 2018, The evolution of a colluvial hollow to a fluvial channel with periodic steps following two transformational disturbances: A wildfire and a historic flood: Geomorphology, v. 309, p. 121-130, https://doi.org/10.1016/j.geomorph.2018.01.003.
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | The evolution of a colluvial hollow to a fluvial channel with periodic steps following two transformational disturbances: A wildfire and a historic flood |
| Series title | Geomorphology |
| DOI | 10.1016/j.geomorph.2018.01.003 |
| Volume | 309 |
| Year Published | 2018 |
| Language | English |
| Publisher | Elsevier |
| Contributing office(s) | Geologic Hazards Science Center |
| Description | 10 p. |
| First page | 121 |
| Last page | 130 |