barrierfall

Barrierfall is a term used in hydrology and geomorphology to describe a waterfall that forms where a river encounters a barrier that restricts flow and creates an abrupt drop. The barrier can be natural, such as a resistant rock ledge, lava flow, or moraine, or engineered, such as a dam or levee. The resulting crest and fall are shaped by the geometry of the barrier, the vigor of the stream, and the lithology of the underlying bedrock.

Formation and morphology often involve a combination of factors. A resistant lip or dam-type barrier can cause the river to pond upstream and overflow at a localized crest, producing a vertical or near-vertical fall. Alternatively, a barrier created by sediment aggradation or a landslide can block flow and force overflow along a distinct crest. The downstream plunge pool, width of the fall, and whether the fall is a single drop or a multistep sequence depend on lip geometry, flow regime, and rock hardness.

Occurrence and study of barrierfalls focus on geomorphological processes and their ecological and engineering implications. Barrierfalls influence sediment transport, water surface profile, and habitat connectivity, and they may be considerations in dam-removal projects, river restoration, or flood risk assessments.

See also: waterfall, knickpoint, dam-related geomorphology, lip geomorphology, barrier island (related barrier concepts).