Newswise — February 17, 2020 – Alluvial soils are soils deposited by surface water. You’ll find them along rivers, in floodplains and deltas, stream terraces, and areas called alluvial fans. The Soil Science Society of America’s (SSSA) February 15th Soils Matter blog explores the definition and importance of alluvial soils.

According to blogger Matthew Ricker, “This is an important category of soils. They provide many functions in our ecosystem. Alluvial soils remove sediments and nutrients flowing in the adjacent water. They can also remove other contaminants from rivers and improve water quality for downstream communities!”

All alluvial soils form by flooding. Because floods periodically deposit new sediment at the surface, alluvial soils can have a unique layered look. Dark and light colors alternate, along with assorted sizes of gravel particles. This unique layering process is called stratification.

In many places around the world there are distinctly different soil colors, chemical properties, and human artifacts buried in floodplains. These allow scientists to reconstruct human occupation and land use history.

To learn more about alluvial soils and their benefits to society, read the entire blog post: https://soilsmatter.wordpress.com/2020/02/15/what-are-alluvial-soils.  

Follow SSSA on Facebook at https://www.facebook.com/SSSA.soils, Twitter at SSSA_Soils. SSSA has soils information on www.soils.org/discover-soils, for teachers at www.soils4teachers.org, and for students through 12th grade, www.soils4kids.org.

The Soil Science Society of America (SSSA) is a progressive international scientific society that fosters the transfer of knowledge and practices to sustain global soils. Based in Madison, WI, and founded in 1936, SSSA is the professional home for 6,000+ members and 1,000+ certified professionals dedicated to advancing the field of soil science. The Society provides information about soils in relation to crop production, environmental quality, ecosystem sustainability, bioremediation, waste management, recycling, and wise land use.

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Newswise: What are alluvial soils?

Credit: M.C. Ricker

Caption: Photograph from eastern Pennsylvania showing floodplain deposits from three distinct stages of watershed land use (picture tape in centimeters). The lowest material (below 60 cm) is old fertile alluvium that has a thick plow layer from agriculture in the 19th century. On top of this is stratified industrial coal washings (20-60 cm) from the early 20th century that buried this once fertile farmland in industrial waste. The upper most sandy material (0-20 cm) is human transported material from the construction of a nearby road in the past decade. This one soil profile clearly shows the evidence of human impacts from agriculture, industrial coal mining, and more modern suburban construction over the past 300 years.

Newswise: What are alluvial soils?

Credit: M.C. Ricker

Caption: Photograph from eastern Pennsylvania (picture tape in centimeters) showing black alluvium deposited from industrial coal mining (upper 60 cm). The darker area was deposited on top of the previously fertile brown and red native floodplain soil. This soil is nearly 100 km downstream from the active mines, illustrating how knowing watershed characteristics is the key to understanding alluvial soil properties.

Newswise: What are alluvial soils?

Credit: M.C. Ricker

Caption: Fertile alluvial soil in central Pennsylvania (tape in centimeters). This floodplain soil is formed from erosion of prime farmland in the watershed, which transfers nutrients to the floodplain. The loamy upper material effectively holds water in the plant root zone and the rounded gravelly base (below 90 cm) allows for drainage of excess water from the root zone.