Sedimentation of rivers is a major concern in South Africa, yet there is no sediment-specific tool for monitoring the effect of sediment stress on riverine ecosystems. Using a novel trait-based approach (TBA), we developed a macroinvertebrate-based sediment biomonitoring index (SBI). South African macroinvertebrates were classified into two vulnerability groups in relation to the potential effects of sediments in riverine ecosystems as well as the trait attributes possessed by each macroinvertebrate family. Forty-eight macroinvertebrate families were designated as vulnerable to sediment stress. Forty-four families were designated as resilient to or tolerant of sediment impact. The index was then tested in selected rivers in South Africa considered to be primarily sediment influenced. The index proved responsive and indicated that the rivers ranged between being minimally sedimented and heavily sedimented. When regressed against turbidity, total suspended solids and embeddedness, the index also proved responsive. Overall, the index can be used as a stressor-specific biomonitoring tool in Southern Africa.