Ulkokaarre

Ulkokaarre is a Finnish term that translates to "outer arc" or "outer curve." In geography, it refers to the outer edge of a meander in a river or stream. Rivers naturally form bends or meanders as they flow across a landscape. The water velocity is not uniform across the width of the river channel. On the outside of a curve, the water flows faster. This increased velocity leads to greater erosional forces, causing the outer bank to be worn away and steepened.

Conversely, the inner side of a meander experiences slower water flow. This results in deposition of sediment, creating a gentler slope known as an inner kaarre or slip-off slope. Over time, the continuous erosion on the ulkokaarre and deposition on the inner kaarre can cause meanders to become more pronounced. Eventually, a meander loop may become so exaggerated that it is cut off from the main river channel, forming an oxbow lake. The concept of ulkokaarre is fundamental to understanding fluvial geomorphology and the processes that shape river landscapes.