Predicting the probability of concentrated flow occurrence using a dynamic approach on high-resolution soil surface data

Authors: Nouwakpo, Sayjro; AL-HAMDAN, OSAMA - Texas A&M University, Kingsville; Williams, Christopher; SPAETH, KENNETH - Natural Resources Conservation Service (NRCS, USDA)

Submitted to: Catena
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/29/2026
Publication Date: 5/4/2026
Citation: Nouwakpo, S.K., Al-Hamdan, O., Williams, C.J., Spaeth, K. 2026. Predicting the probability of concentrated flow occurrence using a dynamic approach on high-resolution soil surface data. Catena. 270. Article 110191. https://doi.org/10.1016/j.catena.2026.110191.
DOI: https://doi.org/10.1016/j.catena.2026.110191

Interpretive Summary: Concentrated flow erosion, occurs when runoff accumulates and flows in narrow channels on the hillslope. This form of erosion is often associated with accelerated soil erosion and off-site impairment of water bodies. Predicting the probability that runoff will become concentrated is crucial to accurate soil erosion modeling but few models exist to achieve this. In this study, we propose a methodology to quantify the probability of concentrated flow occurrence from three-dimensional surfaces of 6 m x 2 m erosion plot by applying synthetic experiments on digitized soil surfaces. The study also provides the first conceptual framework to compute and predict the spatial extent of the concentrated flow network as the number of flow paths (NFP). Pfc and NFP were positive functions of runoff rate, bare ground, canopy cover (NFP only), and clay content while rock cover had an attenuating effect on Pfc. These results are consistent with previously published functions for the probability of flow concentration.

Technical Abstract: Concentrated flow erosion, one of the major mechanisms of erosion by water, is often an indicator of accelerated soil erosion and off-site sediment delivery. While flow hydraulics in a concentrated flow pathway is well understood process, thanks to years of research in the domain, much less is known about the probability of flow concentration occurrence and the spatial extent of the active concentrated flow network. In this study, we propose a methodology to quantify the probability of concentrated flow occurrence from three-dimensional surfaces of 6 m x 2 m erosion plot by applying synthetic rainfalls followed by flow routing and channel cross section analyses in digital space. The probability of flow concentration (Pfc) was expressed as a logistic regression predicting the odds that concentrated flow, referenced to a conceptually defined equivalent flow path area (Afpe), exceeds a given threshold. The study also provides the first conceptual framework to compute and predict the spatial extent of the concentrated flow network as the number of flow paths (NFP). Pfc and NFP were positive functions of runoff rate, bare ground, canopy cover (NFP only), and clay content while rock cover had an attenuating effect on Pfc. These results are consistent with previously published functions for the probability of flow concentration.