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How do meltwater streams create braided channels in front of glaciers?

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esker: Nunavut — glacial landform Eskers, or narrow ridges of gravel and sand left by a retreating glacier, wind through western Nunavut, Canada, near the Thelon River.

Meltwater streams create braided channels in front of glaciers primarily due to the high volume of sediment they carry and the extreme variability of their water flow.12

As these streams emerge from the glacier snout, they are typically laden with debris—ranging from sand to coarse gravel—picked up from beneath or within the ice. Once the water leaves the confinement of the glacier's ice tunnels, it spreads out, causing a decrease in velocity. Because the stream's ability to transport material depends on its velocity, this slowdown forces the water to deposit its sediment load.13

This deposition chokes the original stream channel with sand and gravel bars. The stream is then forced to divert its course around these obstacles, breaking into multiple, winding, and shifting channels. This process is further intensified by the highly variable nature of meltwater discharge, which fluctuates significantly based on daily and seasonal temperatures. The resulting braided pattern is characterized by a high width-depth ratio and mobile bed material, commonly found on outwash plains where valleys are being filled with incoherent, coarse sediment.124