The area upon which Oak Hill is located is characterized by mostly hilly terrain. Limestone rimrock structures are commonplace in Oak Hill. The community is located above the Edwards and Trinity aquifers, resulting in the abundance of caves, sinkholes, karst features, and springs, which allow for recharge and discharge of groundwater. In addition, Barton, Slaughter, and Williamson creeks, which all lead to the nearby Colorado River, flow through Oak Hill. Riparian woodlands exist along areas of these creeks. Threatened bird species, including the golden-cheeked warbler (Setophaga chrysoparia) and the black-capped vireo (Vireo atricapilla) live in some areas of Oak Hill.