flodgrus

Flodgrus is a geological term used in Swedish to denote coarse gravels deposited by rivers, i.e., river gravel or fluvial gravel. These gravels consist predominantly of rounded to subrounded pebbles and cobbles, often with sand and silt, and occur in alluvial settings such as floodplains, river bars, and terraces.

Formation and properties: Flodgrus forms when rock fragments are eroded upstream, transported by river flow, and deposited when the energy of the current decreases. Clast sizes typically range from gravel to cobble, with particles becoming more sorted downstream or in zones where flow velocity fluctuates. The material is usually well rounded due to abrasion and may occur as bar deposits or as basal gravels beneath finer sediments.

Distribution and environments: River gravels are common along active river valleys worldwide. They accumulate in braided and meandering channel belts, point bars, and paleo-floodplains, reflecting river dynamics, sediment supply, and flow regimes.

Uses and economic importance: Flodgrus is widely used as construction aggregate for concrete and road bases, as drainage material, and in landscaping. The quality varies with grain size distribution, cementation, and contamination by clay or organic matter.

Environmental considerations: Extraction from river gravels can impact aquatic habitats, alter sediment transport, and increase turbidity. Sustainable quarrying practices, regulatory oversight, and proper permitting are important to mitigate ecological effects.

See also: Alluvium, Fluvial geology, Gravel pit.