Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Desert Streams: Deceptively Simple

24.10.2014

The simple topography of dryland channels presents an interesting paradox according to scientists from UCSB’s Earth Research Institute

Volatile rainstorms drive complex landscape changes in deserts, particularly in dryland channels, which are shaped by flash flooding. Paradoxically, such desert streams have surprisingly simple topography with smooth, straight and symmetrical form that until now has defied explanation.


Dryland channels exhibit very simple topography despite being shaped by volatile rainstorms. Photo Credit: Katerina Michaelides


Humid channels feature complex topography with river bars, pools or riffles. Photo Credit: Michael Singer

That paradox has been resolved in newly published research conducted by Michael Singer and Katerina Michaelides, associate researchers at UC Santa Barbara’s Earth Research Institute. The pair show that simple topography in dryland channels is maintained by complex interactions among rainstorms, the stream flows these storms generate in the river channel and sediment grains present on the riverbed. Their findings appear today in the journal Geology.

Desert streams flow only during infrequent but intense rainstorms, and when they do, only parts of the channel contain water, making the flow irregular and erratic. One rainstorm may erode sediment grains in one section of the channel, while another storm moves sediment in a different area.

“Given this localized sediment movement during rainstorms, one might expect desert channels to contain mounds of sediment that undulate down the stream course reflecting the irregular flow, but they don’t,” Singer said. “The water produced in the channel only flows partially down the stream and then stops because it seeps into the riverbed, and there’s not enough water from upstream to replace it, so it just disappears.”

Because desert river channels do not feature the river bars, pools or riffles common in perennial streams, they decline in elevation downstream very smoothly. According to the researchers’ findings, feedback between two variables — complex water and sediment movements — shape such basins.

Singer and Michaelides used data collected from the Rambla de Nogalte in southeastern Spain to model these dryland channel variables. The area has a semi-arid climate with mean annual rainfall of around 14 inches, which occurs during convective rainstorms, producing large floods that recur about once a decade.

They found that dryland channel width fluctuates downstream. Their observations show that grain size (roughness) also fluctuates from sand to gravel a downstream direction.

“There’s feedback between this fluctuating width and fluctuating grain size,” Singer said. “The stream flow is generated in a discontinuous pattern along the channel. Some rainstorms produce a bit of topography in some parts of the channel. Other spatial configurations of flow generated by storms destroy that topography so the variability of the rainstorms interacting with this channel are creating and destroying the topography constantly to keep it in this simple form.”

Singer and Michaelides also produced simulations of extreme flows to determine the volume of flow necessary to reshape the channel completely. They examined the longitudinal variability of sediment flow as well as sediment storage to find the channel-shaping threshold. This threshold reshapes the entire channel and makes it smooth again. “It’s a really significant threshold that tells us the magnitude of the flood necessary to reshape the channel,” Singer said.

“Semi-arid and arid river systems are extremely important to the populations that live around them,” he concluded. “Water resources are obviously a huge limitation in the development of societies, and a lot of water is being progressively diverted for irrigation, water use and other purposes, so those can further affect the spatial patterns of where flow is in these channels and potentially impact the processes of where topography develops in the river channel. Humans can inadvertently have an impact on the shape and form of river channels like these.”

Contact Info: 

Julie Cohen
julie.cohen@ucsb.edu
(805) 893-7220

Julie Cohen | Eurek Alert!
Further information:
http://www.news.ucsb.edu/2014/014459/desert-streams-deceptively-simple

More articles from Earth Sciences:

nachricht Monitoring lava lake levels in Congo volcano
16.05.2018 | Seismological Society of America

nachricht Ice stream draining Greenland Ice Sheet sensitive to changes over past 45,000 years
14.05.2018 | Oregon State University

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Explanation for puzzling quantum oscillations has been found

So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics

Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...

Im Focus: Dozens of binaries from Milky Way's globular clusters could be detectable by LISA

Next-generation gravitational wave detector in space will complement LIGO on Earth

The historic first detection of gravitational waves from colliding black holes far outside our galaxy opened a new window to understanding the universe. A...

Im Focus: Entangled atoms shine in unison

A team led by Austrian experimental physicist Rainer Blatt has succeeded in characterizing the quantum entanglement of two spatially separated atoms by observing their light emission. This fundamental demonstration could lead to the development of highly sensitive optical gradiometers for the precise measurement of the gravitational field or the earth's magnetic field.

The age of quantum technology has long been heralded. Decades of research into the quantum world have led to the development of methods that make it possible...

Im Focus: Computer-Designed Customized Regenerative Heart Valves

Cardiovascular tissue engineering aims to treat heart disease with prostheses that grow and regenerate. Now, researchers from the University of Zurich, the Technical University Eindhoven and the Charité Berlin have successfully implanted regenerative heart valves, designed with the aid of computer simulations, into sheep for the first time.

Producing living tissue or organs based on human cells is one of the main research fields in regenerative medicine. Tissue engineering, which involves growing...

Im Focus: Light-induced superconductivity under high pressure

A team of scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg investigated optically-induced superconductivity in the alkali-doped fulleride K3C60under high external pressures. This study allowed, on one hand, to uniquely assess the nature of the transient state as a superconducting phase. In addition, it unveiled the possibility to induce superconductivity in K3C60 at temperatures far above the -170 degrees Celsius hypothesized previously, and rather all the way to room temperature. The paper by Cantaluppi et al has been published in Nature Physics.

Unlike ordinary metals, superconductors have the unique capability of transporting electrical currents without any loss. Nowadays, their technological...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Save the date: Forum European Neuroscience – 07-11 July 2018 in Berlin, Germany

02.05.2018 | Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

 
Latest News

Supersonic waves may help electronics beat the heat

18.05.2018 | Power and Electrical Engineering

Keeping a Close Eye on Ice Loss

18.05.2018 | Information Technology

CrowdWater: An App for Flood Research

18.05.2018 | Information Technology

VideoLinks
Science & Research
Overview of more VideoLinks >>>