The Dobra is a river located mostly in the Karlovac County in the Republic of Croatia. It is 104.2 kilometres long and its basin covers an area of 1,428 square kilometres. Its name is the feminine form of the Croatian adjective meaning "good" but it is over simplistic folk etymology. The river name probably comes from the Celtic transl. cel – transl. dubrum, dubron m…The Dobra is a river located mostly in the Karlovac County in the Republic of Croatia. It is 104.2 kilometres long and its basin covers an area of 1,428 square kilometres. Its name is the feminine form of the Croatian adjective meaning "good" but it is over simplistic folk etymology. The river name probably comes from the Celtic transl. cel – transl. dubrum, dubron meaning 'water', Illyrian δυβρις 'deep' or Old Slavonic dъbrь also 'deep' or 'valley'.