Movement of tractive sediment from disturbed lands

The Smoky Creek basin of the coal area of northeastern Tennessee shows extensive evidence of tractive movement of coarse sediment from mined tributary basins into the main channel. Coal-rich gravel bars and flood-plain debris are common below tributaries. Using a combination of techniques including channel-geometry and bar measurements, sediment sampling for rock-debris and coal size distributions, and botanical dating of flood events and geomorphic features, an average annual yield of 65 metric tons per square kilometer (187 tons per square mile) for tractively moved sediment has been calculated for the period 1977 to 1982. This value, 8 percent of the total sediment load, is probably an underestimate owing to the method of calculation. Slightly more than half of the traction load is coal, which moves through the basin within a few years. Rock debris, however, appears to require years to decades to move similar distances.