Kiesarm

Kiesarm is a geomorphological term referring to a secondary river channel, or arm, whose bed and banks are dominated by gravel sediments. The name derives from Dutch kies, meaning gravel, and arm, meaning an offshoot of a river. The term appears primarily in Dutch- and German-language hydrological literature.

Formation and characteristics: Kiesarms develop in gravel-rich braided or wandering river systems. High-energy floods transport coarse material that forms gravel bars and splits the main channel, creating an additional offshoot. These arms often display a wide, shallow gravel bed, with variable flow, frequent avulsions, and rapid responsiveness to sediment supply and discharge changes.

Distribution and usage: While not universal, the term Kiesarm is used in regional riverine studies across the Low Countries and parts of Central Europe to distinguish gravel-dominated side channels from finer-sediment channels. It is related to, but distinct from, terms such as side channel, channel avulsion, and gravel chute.

Ecology and management: Kiesarms contribute to habitat diversity and groundwater recharge. They can act as hydraulic relief valves during floods but are susceptible to siltation, vegetative encroachment, and gravel extraction. River engineers consider Kiesarms in flood risk assessment, habitat restoration, and sediment management plans.

See also: Braided river, side channel, sediment transport, fluvial geomorphology.