Veleka (in Turkish : Kocadere, Kojadere ) is a river in Turkey and Bulgaria , Burgas region - Malko Tarnovo and Tsarevo municipalities , flowing into the Black Sea. Its entire length is 147 km, of which 24 km on Turkish territory, and 123 km on Bulgarian territory, which ranks it 21st among Bulgarian rivers. The Veleka River is the largest river in Southeastern Bulgaria and along the Southern Black Sea coast.