Sources of River Corridor Resilience to Disturbance

As a geomorphologist, I often think about how landscapes have changed due to natural or human disturbance. Below are questions I have been exploring around how rivers respond following disturbances on both short and long timescales. 

Biogeomorphic Influences on River Corridor Resilience to Wildfire Disturbance

In Wohl, Marshall et al. (2022), Wohl, Marshall et al. (2024a), and Wohl, Marshall et al. (2024b), we use a headwater stream in the Front Range of Colorado as a case study for how a system responds following a disturbance cascade (wildfire, convective storm flooding, debris flows) to examine how spatial heterogeneity of wood 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 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 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, 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 whether a system is resistant, resilient, or sensitive. We find that (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 post-fire 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.

Conceptual diagram of how interactions in the river corridor create and maintain spatial heterogeneity that fosters reach-scale attenuation of downstream fluxes and network-scale resilience to wildfire disturbance. 

Post-wildfire debris flow and flooding, captured in the images above on a trail camera. Note the time stamps in the righthand corner of each photo. 

Wohl, E., Marshall, A., Triantafillou, S., Mobley, M., Morrison, R. (2024b). “Distribution of Logjams in Relation to Lateral Connectivity in the River Corridor.” Geomorphology. 

https://doi.org/10.1016/j.geomorph.2024.109100 

Wohl, E., Marshall, A., Scamardo, J., Rathburn, S. (2024a). “Biogeomorphic processes, spatial heterogeneity, and river corridor resilience to stand-killing wildfire” GSA Special Papers. https://doi.org/10.1130/2024.2562(08) 

Wohl, E., Marshall, A., Scamardo, J. White, D., Morrison, R.R. (2022). Geomorphic Influences of River Corridor Resilience to Wildfire Disturbances in a Mountain Stream of the Southern Rockies, USA. Science of the Total Environment. https://doi.org/10.1016/j.scitotenv.2022.153321