As a boat approached the canal traveling south on the Catawba River, the patroon, or river boat pilot, first saw the diversion dam. The dam consisted of piles of loose stone on the river bottom. It projected from the bank at roughly forty degrees and did not completely cross the river. It was designed to keep a sufficient water supply flowing through the canal when the river was low and to maintain an area of calm water to prevent boats from being swept into the shoals during floods.