The Gorjanci Hills are a forested mountain range in the south-eastern part of Slovenia. They are rich in water, which flows into numerous streams. The larger streams include Klamfer, Babni potok, Sovpat, Šumeči potok, Pendirjevka, Kobila, and Sušica. During heavy rainfall, they turn into torrents. The present contribution will focus on the major flash floods of these streams in the 1930s and their regulation to prevent flooding.