[1] The river originates under the name Dudenska reka from a spring at an altitude of 440 m, southeast of the summit of Chukara (466 m) in the Bosna Ridge of the Strandzha mountain range.

Downstream of the village it turns east and forms a wide swampy valley until its mouth in a dike-protected riverbed.

The marshy area at is mouth is known as Dyavolsko blato (Bulgarian: Дяволско блато, "devil's swamp"), covered by common reed ("Phragmites australis").

The swamp is fed by a freshwater spring, has an area of 2.7 km2 and depth up to 3 m.[1] Its drainage basin covers a territory of 133 km2 and borders the drainage basins of the Ropotamo to the north and west, the Veleka to the southwest, and the Karaagach to the south and southeast, all of them flowing into the Black Sea.

Two kilometers upstream from the village is located Yasna Polyana Reservoir, built for irrigation and potable water supple for many settlements along the southern Bulgarian Black Sea Coast.