We used an experiment and regression analyses to quantify effects of spatial variation in habitat structure abundance on a riverine macroinvertebrate community under winter conditions. Concrete slabs (0.21 m²; n = 24) with different numbers of stones (mean individual stone surface area = 6.44 cm²) attached to upper faces were placed in the James River and retrieved after 28 d. Macroinvertebrate abundance and taxonomic richness on slabs were significantly positively related to stone abundance. Total macroinvertebrate abundance and abundance of oligochaetes (Nais spp.), Asiatic clams (Corbicula fluminea), caddisflies (Leptoceridae), riffle beetles (Elmidae) and stoneflies (Strophopteryx sp.) were linearly related to stone abundance. However, nonlinear relationships occurred between stone abundance and macroinvertebrate taxonomic richness and between stone abundance and abundance of dragonflies (Erpetogomphus sp.), caddisflies (Hydropsychidae), chironomids (Eukiefferiella spp.), mayflies (Ephemerellidae) and stoneflies (Taeniopteryx sp.). Nonlinear relationships were usually characterized by dramatic increases in macroinvertebrate abundance and taxonomic richness across a gradient of increasing stone abundance when abundance was low (0–43 stones/0.08 m² slab face; 0–40% of slab face covered by stones), but weak responses to additional stones at higher stone abundance (84–160 stones/0.08 m²; 89–96% cover). These nonlinear relationships reflected similar nonlinear relationships between abundance of stones and particulate matter. We conclude that small quantities of habitat structure have significant positive effects on macroinvertebrate abundance and diversity in the James River during winter. At a local scale, habitat structure promotes macroinvertebrate colonization and retention by increasing habitat diversity. Stones and similar physical objects also indirectly benefit macroinvertebrates by trapping particulate matter that provides animals with food and additional habitat.