  the duck river,  long,u.s. geological survey. national hydrography dataset high-resolution flowline data. the national map, accessed june 8, 2011 is the longest river located entirely within the u.s. state of tennessee. free flowing for most of its length, the duck river is home to over 50 species of freshwater mussels and 151 species of fish, making it one of the most biologically diverse rivers in north america. the duck river drains a significant portion of middle tennessee. it rises in hills near an area of middle tennessee known as the "barrens", an area with enough rainfall to support a woodland but which white settlers found already deforested upon their arrival. (several theories have been advanced to explain this phenomenon.) it enters the city of manchester and meets its confluence with a major tributary, the little duck river, at old stone fort state park, named after an ancient native american structure between the two rivers believed to be nearly 2,000 years old. other major towns along the duck include shelbyville, columbia, and centerville. above shelbyville, the duck is impounded by normandy dam, a tennessee valley authority project of the early 1970s which was built for flood control and recreation. normandy was not equipped for power generation as were previous tva dams built in middle tennessee. the structure was named for the hamlet of normandy, which is nearby. the resultant reservoir occupies over  of what was previously prime land for agriculture. further downstream, shelbyville is protected from potential duck river flooding by levees and floodgates. a dam constructed by the tennessee electric power company across the river adjacent to downtown shelbyville is a relic of the early electrical development of the area prior to the establishment of the tennessee valley authority. thumb|right|250px|blue hole falls along the duck river near manchester downstream in maury county is the yanahli wildlife preserve, occupying land which was meant to be another tva reservoir. the columbia dam was never completed, however, when an endangered species of mussel w
Landforms_of_Coffee_County,_Tennessee Landforms_of_Humphreys_County,_Tennessee Rivers_of_Tennessee