Effect of near-surface hydrology on soil strength and mobility
History has repeatedly demonstrated the potentially negative influence of near-surface hydrology on military mobility. Increased moisture and saturation in soil results in a transition from solid to somewhat liquid states. As soil approaches the liquid state, the shear strength available for supporting traffic of ground vehicles or aircraft diminishes. Historical engagements elucidate the importance for armies to recognize soil conditions that could compromise manoeuvre. Since World War II, the US Army has pursued research aimed at equipping soldiers with the tools and knowledge needed to account for the impact of near-surface hydrology on mobility. Significant portions of the research have been focused on characterizing soil trafficability as a controlling factor in ground vehicle mobility and on developing methods for rapidly assessing soil conditions to ensure adequate bearing capacity for expediently constructed roads and airfields. In contrast, hydrological conditions can also produce extremely dry soil with potential for surface layers to break down under ground vehicle and aircraft traffic loadings, resulting in a propensity for extreme dust generation, an entirely different problem for military mobility that the research has also been addressing. Mobility problems associated with these adverse soil conditions have not been eliminated, but the research has produced significant advancements.