The Big South Fork of the Cumberland River is a river in the U.S. states of Tennessee and Kentucky. It is a major drainage feature of the Cumberland Plateau, a major tributary of the Cumberland River system, and the major feature of the Big South Fork National River and Recreation Area. Physical geography The Big South Fork begins at the confluence of the New River and the Clear Fork in Scott County, Tennessee, and flows northwest, northeast, and north until ending at Lake Cumberland in McCreary County, Kentucky, near the town of Burnside. It is the third largest tributary of the Cumberland River, and is free flowing for a distance of approximately before being affected by the headwaters of the lake. The terrain furthest upstream near the confluence is the most rugged, with reliefs of as much as . This area is characterized by dendritic draining patterns and narrow gorges, with valleys strewn with large boulders fallen from cliffs above. Major formations include natural arches, mesas, chimneys, cracks and rock shelters. The terrain becomes less rugged as the river travels northward, with reliefs of between and . Soil in the area is divided between two groups. The first is primarily made up of Ramsey, Hartsells, Grimsley, and Gilpin soils and is located adjacent to the river gorge. The second consists of Hartsells, Lonewood, Ramsey, and Gilpin soils and is found on the nearby plateau. Hydrology The river draws water from a drainage basin of Carboniferous rock in the Cumberland Plateau. Taken together, the Big South Fork and its tributaries drain between and , of which about 17% is covered by the associated National Recreation Area. The maximum recorded water flow on the Big South Fork was , the minimum recorded was , and the river averages a flow of . Around half of the Big South Fork's annual streamflow occurs during the months of January through March, and the lowest streamflow typically occurs during September and October. Along the river basin, water drops from an maximum original elevation of above sea level at Peter's Bridge on the Clear Fork, to where the waters meet the Cumberland. Between the confluence of the New River and Clear Fork, and Leatherwood Ford the river has an average gradient across of 20 feet per mile (fpm), and a maximum gradient of 40 fpm. Major tributaries of the Big South Fork include: New River Clear