Subscribe free to our newsletters via your
. Earth Science News .




WATER WORLD
Rivers flow differently over gravel beds
by Staff Writers
Champaign IL (SPX) Oct 20, 2014


River researchers used a specially constructed model to study how water flows over gravel river beds. Postdoctoral researcher Gianluca Blois (left) and professor Jim Best also developed a technique to measure the water flow between the pore spaces in the river bed. Image courtesy L. Brian Stauffer.

River beds, where flowing water meets silt, sand and gravel, are critical ecological zones. Yet how water flows in a river with a gravel bed is very different from the traditional model of a sandy river bed, according to a new study that compares their fluid dynamics. The findings establish new parameters for river modeling that better represent reality, with implications for field researchers and water resource managers.

"The shallow zones where water in rivers interacts with the subsurface are critical environmentally, and how we have modeled those in the past may be radically different from reality," said Jim Best, a professor of geology, geography and geographic information science at the University of Illinois.

"If you're a river engineer or a geomorphologist or a freshwater biologist, predicting where and when sediment transport is going to occur is very important. This study provides us with a very different set of conditions to look at those environments and potentially manage them."

Best and postdoctoral researcher Gianluca Blois led the study at the U. of I., in collaboration with colleagues in the United Kingdom. The team published its findings in the journal Geophysical Research Letters.

The researchers used a specially constructed flume in the Ven Te Chow Hydrosystems Laboratory at Illinois to experimentally compare scenarios ranging from the traditional model of an impermeable river bottom to a completely permeable river bed - a collection of spheres that simulate gravel.

The researchers used a technique called particle image velocimetry (PIV), a widely used method for quantifying how water flows over a model river bed, pioneered at the U. of I. in the 1980s. Best and Blois developed a method to use PIV endoscopically to study, for the first time, fluid flow within the small spaces between the gravel. This allowed them to quantify flow within the river bed and link it to the stream flow above.

They found that, in the scenario that simulates a gravel bed, the patterns of flow velocity above the bed and the distribution of forces on the river bed were dramatically different from the models on which all previous work has been based. Their experimental scenarios also disproved one popular theory that explained the difference between classic models and field observations for the formation of bed topography, such as dunes.

"Bedforms formed in fine sediments are known to be substantially different from those formed in gravel beds, but we just didn't know why," Blois said.

"People before us suggested that those differences were due to the roughness of the grains. But we introduced the bed permeability, just like real rivers. This, with our new measurement technique, allowed us to demonstrate that most of the stress variation is actually coming from fluid emerging from the permeable bed, rather than roughness."

The maps of water flow that the experiments produced could lead to better predictive models, so that researchers can more accurately predict and study how nutrients and pollutants travel and accumulate in rivers. These new models also could provide insight into the growth and behavior of organisms that thrive in the narrow zone where river flow meets the river bed.

"For example, when salmon spawn in gravel-bed rivers, they basically make a depression in the gravel, into which they lay their eggs," Best said. "By doing that, not only do they protect the eggs, but they create a bump in the sediment that creates a pressure distribution that would keep fine grains from going into the bed, which would be detrimental to the eggs. It's fascinating that fish actually take advantage of these flow dynamics."

The researchers are working with collaborators around the world to study how permeability affects turbulence above the bed, how this affects the organisms that grow in the pore spaces, and how tiny particles and dissolved substances accumulate in porous riverbeds.

"It's going to change the way we conceptualize these systems and model them," Blois said. "We're trying to raise awareness of the fact that we are now able to measure the complex flow dynamics in these challenging environments, and that's going to open up a new paradigm for river research."

The UK Natural Environmental Research Council supported this work.


Thanks for being here;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.
SpaceDaily Contributor
$5 Billed Once


credit card or paypal
SpaceDaily Monthly Supporter
$5 Billed Monthly


paypal only


.


Related Links
University of Illinois
Water News - Science, Technology and Politics






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle








WATER WORLD
Lake Erie increasingly susceptible to large cyanobacteria blooms
Ann Arbor MI (SPX) Oct 20, 2014
Lake Erie has become increasingly susceptible to large blooms of toxin-producing cyanobacteria since 2002, potentially complicating efforts to rein in the problem in the wake of this year's Toledo drinking water crisis, according to a new study led by University of Michigan researchers. Since the detection of the toxin microcystin left nearly half a million Ohio and Michigan residents with ... read more


WATER WORLD
Natural disasters killed over 22,000 in 2013: Red Cross

Rescuers airlift 154 to safety after deadly Nepal storm

Glitzy Russian TV drama brings Chernobyl to new generation

Chobani yogurt founder gives $2mn for Syria/Iraq refugees

WATER WORLD
Engineers find a way to win in laser performance by losing

Unstoppable magnetoresistance

Sticky business: bonding ultrastable space missions

Tailored flexible illusion coatings hide objects from detection

WATER WORLD
Rivers flow differently over gravel beds

New study shows the importance of jellyfish falls to deep-sea ecosystem

Lake Erie increasingly susceptible to large cyanobacteria blooms

Researchers solve riddle of the rock pools

WATER WORLD
Icebergs once drifted to Florida, new climate model suggests

Peru glaciers shrink 40% in 44 years: government

Canada Inuits reach EU deal to resume seal-product exports

What is Happening with Antarctic Sea Ice

WATER WORLD
Building a bridge from basic botany to applied agriculture

Stomping out grape disease one vineyard at a time

Plant communities produce greater yield than monocultures

Are there enough fish to go around?

WATER WORLD
Journey to the Center of the Earth

New method helps predict extreme floods in Andes

Search for missing on Japan volcano called off until next year

Bermuda braces for 'dangerous hurricane' Gonzalo

WATER WORLD
Nigeria tries 59 soldiers on mutiny charges

Horn free: Lagos tries to tackle noise pollution

27 Chinese and local hostages released in Cameroon: govt

Six UN peacekeepers injured in C. Africa

WATER WORLD
Facebook, Apple to cover women's egg-freezing: report

Buried complex of ancient cult uncovered in Israel

New Antikythera Discoveries Prove Luxury Cargo Survives

Treasure trove of ancient genomes helps recalibrate the human evolutionary clock




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.