The Kollweck flows steadily through the Duenn Forests and drains directly into the Pacific Ocean, without a delta. The vegetation on the banks of the river is relatively monotone, compared to the vegetation surrounding the Done, and consists mainly out of grasses, reeds, mosses, ferns, birches, and pine trees. The river is one of the few places in the world where the rare Pacific salmon Oncorhynchus skyhlan, commonly known as School salmon, spawns. As a consequence, acidity levels and general purity of the water is well-monitored, and fishing is restricted in the spawn season.