Kayan

Course

The Kayan is a large river in Borneo. It is one of the largest and most important rivers in the province of Kalimantan Utara. It rises in the northern part of the island's central mountain range in the Ukeng Mountains and flows in a large delta into the Sulawesi Sea below the provincial capital Tanjung Selor.

Geography and hydrology

The Kayan River rises on Mount Ukeng, passing Tanjung Selor city, and discharges into the Sulawesi Sea, with a total length of about 576 km (358 mi) and a basin size of 33,005 km2 (12,743 mi2), forming a wide area at the upstream and narrower in the center until downstream.

The Kayan River is named after the Kayan Dayak tribe. Its headwaters originate in the Ukeng Mountains at an altitude of about 2,015 m (6,611 ft) above sea level. The river cuts through mountainous areas in a south-east, east-east and then north-east direction with high gradient rapids. It flows over Tanjung Selor for more than 70 km through coral and limestone hills to the town. Its banks are typically lined with nipas, with some coconut trees.

Ecology and economy

The Bulungan district of the Kayan River in northern Kalimantan is characterised by rich biodiversity and includes ecosystems such as lowland tropical rainforest, montane forest, peat swamps, mangroves and karst. The Kayan Delta is home to at least 6 native mangrove species (Rhizophora apiculata, Osbornia octodonta, Lumnitzera littorea, Avicennia sp., Rhizophora sp., Sonneratia sp.). The interior of the delta is dominated by nipah (Nypa fruticans), while parts of the delta are home to mixed freshwater and saltwater ecosystems.

The Kayan is vital for communities living along the river and in its delta, as they depend on it for freshwater, fisheries and agriculture. Dayak people living along the river depend on farming, agriculture and fishing.