8352 - ASSESSING THE STRENGTH OF RIVER BOTTOMS FOR VEHICLE FORDING

Paper presented at ISTVS 2025 | 55th Conference of the International Society for Terrain-Vehicle Systems https://doi.org/10.56884/JF8WN0WV

Authors: Sally Shoop, John Eylander, Theodore Letcher, Kathleen Staebell

Keywords: River Crossing; Fluvial Geomorphology; Gravel; Strength; Low Water Crossing; River Sediments; River Bottom; Riverbed; Grain Size; Coarse grain; Wet Gap Crossing; Measurement; Vehicle Fording

Abstract:

Vehicle fording, a means of wet gap crossing, is difficult to study because of numerous requirements to ensure safe crossing based on both the vehicle and the changing characteristics of the river. While some of these requirements are well-known, others are so complex and variable that they remain ill-defined. This paper will review river crossing guidance with a special interest on river characteristics that are seasonally variable. While seasonal changes in river flow rate are somewhat predictable, they rely on many assumptions about the river bathymetry and discharge. The riverbank conditions can also change drastically with season, affecting ingress and egress. Lastly, the competence of the river bottom (strength and stability) is extremely difficult to estimate remotely or to measure, so this was a primary focus for this research. Recent progress in fluvial geomorphology and the new field called river morphodynamics may help in determining the best places to cross a river based on its adjacent landforms, river type, and available site observations. Equations from fluvial geomorphology and geotechnical engineering are used to relate river conditions to bottom sediment strength. Exploratory field measurements of river bottom strength were performed. Results using a modified static cone penetrometer were analyzed and methodology to evaluation the strength of the river bottom was developed. While data requires extra care to interpret, the results shed light on areas of future research needs. Fording guidance, applicable geomorphology, and recent advancements in terramechanics research for river crossings are summarized to provide context. Field methods, results and future research needs are presented.