What determines the placement of some soils into Hydrologic Group D?

The placement of some soils into Hydrologic Group D is primarily determined by the presence of a high water table which can lead to significant drainage issues. Soils in this category are characterized by high clay content and poor drainage properties, resulting in a high water table that makes them prone to saturation. This saturation can reduce the ability of these soils to absorb rainfall or surface runoff, which increases the likelihood of water pooling and leads to flooding and erosion problems.

This classification is crucial for understanding how water interacts with different soil types during precipitation events, helping in the management and planning of stormwater runoff. The focus on drainage issues emphasizes the need for appropriate mitigation strategies in areas where Hydrologic Group D soils are present. The other choices, which include factors like organic content, soil erosion rates, and permeability, do not directly relate to the characteristics that define Hydrologic Group D.