Alluvium
Alluvium is loose soil or sediments (such as clay, silt, sand, gravel and so on) that is eroded and carried in suspension by flood or river water before being deposited. The material of alluvium is may be unconsolidated, i.e. not formed together into solid rock, and can by picked up or eroded and carried away by moving water before being deposited elsewhere when the water flow slows down. Where the loose alluvial material is consolidated into a stone-like material (or lithological unit), this is known as lithification.
The fine-grained fertile soil that is deposited by water that flows over flood plains or river beds is known as alluvial soil.
Some of the characteristics of alluvial soils include:
- The soil morphology will vary according to the age of the alluvial deposit and how it was formed.
- The textural range of the soil can vary widely from gravel to silty clay.
- Drainage can vary from very poor to free.
- The texture of the soil can vary both vertically and laterally.
- It may contain a large amount of organic matter.
The presence of alluvial deposits may mean that the ground conditions are poor and so can require the construction of a raft foundation, or deep pile foundations. In these conditions, strip or pad foundations would require significant excavation.
Geoarchaeology, Using Earth Sciences to Understand the Archaeological Record, published by Historic England in 2015, defines states: ‘alluvium any water-borne sediment is technically alluvium, but the common usage is for fine-grained floodplain deposits’.
[edit] Related articles on Designing Buildings Wiki
Featured articles and news
The need for a National construction careers campaign
Highlighted by CIOB to cut unemployment, reduce skills gap and deliver on housing and infrastructure ambitions.
AI-Driven automation; reducing time, enhancing compliance
Sustainability; not just compliance but rethinking design, material selection, and the supply chains to support them.
Climate Resilience and Adaptation In the Built Environment
New CIOB Technical Information Sheet by Colin Booth, Professor of Smart and Sustainable Infrastructure.
Turning Enquiries into Profitable Construction Projects
Founder of Develop Coaching and author of Building Your Future; Greg Wilkes shares his insights.
IHBC Signpost: Poetry from concrete
Scotland’s fascinating historic concrete and brutalist architecture with the Engine Shed.
Demonstrating that apprenticeships work for business, people and Scotland’s economy.
Scottish parents prioritise construction and apprenticeships
CIOB data released for Scottish Apprenticeship Week shows construction as top potential career path.
From a Green to a White Paper and the proposal of a General Safety Requirement for construction products.
Creativity, conservation and craft at Barley Studio. Book review.
The challenge as PFI agreements come to an end
How construction deals with inherited assets built under long-term contracts.
Skills plan for engineering and building services
Comprehensive industry report highlights persistent skills challenges across the sector.
Choosing the right design team for a D&B Contract
An architect explains the nature and needs of working within this common procurement route.
Statement from the Interim Chief Construction Advisor
Thouria Istephan; Architect and inquiry panel member outlines ongoing work, priorities and next steps.
The 2025 draft NPPF in brief with indicative responses
Local verses National and suitable verses sustainable: Consultation open for just over one week.
Increased vigilance on VAT Domestic Reverse Charge
HMRC bearing down with increasing force on construction consultant says.
Call for greater recognition of professional standards
Chartered bodies representing more than 1.5 million individuals have written to the UK Government.