Featured Research

from universities, journals, and other organizations

Sand In Sediment Can Predict River Damage

Date:
April 17, 1998
Source:
Johns Hopkins University
Summary:
A Johns Hopkins engineer has developed a method to estimate how quickly a sudden rush of river sediment will flow downstream, aiding analysis of the likely environmental damage.

New method sheds light on a stream's response to land disturbance

A Johns Hopkins University scientist has devised a simple method of estimatinghow quickly excess river sediment--unleashed by natural or man-made landdisturbances--will flow downstream. Peter R. Wilcock's technique, unveiled inthe April 17 issue of the journal Science, may help prevent or correctenvironmental problems that occur when large amounts of fine-grained materialswash into a river.

Forest fires, logging, road construction, urban development and dam operationscan send a rush of sediment into gravel-bed rivers, triggering seriousconsequences, says Wilcock, a professor in the Department of Geography andEnvironmental Engineering. For example, a surplus of sand can degrade thehabitat of fish and other aquatic animals and increase thepotential for flooding along a river.

For this reason, says Wilcock, river managers need to know how quickly thissand will be swept downstream, returning the gravel bed to a healthiercondition. "We want to be able to predict how long it will take for the extrasediment to move through the river," he says.

But predicting how sediment will move has been difficult because the particlescome in many sizes, each moving at a different pace. "The sampling necessaryto analyze all of these sizes would be so extensive as to be impossible,"Wilcock says. "We needed a theory that could be supported by a practicalamount of field observation."

The Hopkins scientist solved this problem by dividing sediment into just twocategories: sand, with grains smaller than 2 millimeters; and gravel, withgrains larger than 2 millimeters. The percentages of these two sizes can bedetermined by wading along the river, which is much simpler and quicker thanother sampling techniques, Wilcock says.

"You need to know the rate at which the sediment will be transported by thestream," he says, "and you want to know whether the fine material--thesand--will move downstream faster than the gravel."

Wilcock's method demonstrates how fast the water must move in order to firstdislodge the sand and gravel from the river bed and begin then moving thematerial.

"Estimates of transport rate are needed to forecast the extent and duration ofriver impacts caused by land disturbance," Wilcock says. "This information isalso needed to guide efforts to restore rivers that have received excessivesediment loadings."

An interesting consequence of this new way of looking at sediment movementthrough rivers is that it demonstrates that an increase in the proportion ofsand in the bed can increase the rate of transport of both the sand and thegravel. "This is encouraging because it suggests that rivers have a naturalability to increase their rate of transporting sediment in response to anincrease in sediment supply," Wilcock says. "This does not remove thenegative impact of fine-grained sediment loading, but it may reduce andshorten it."

Wilcock's research is supported by the Stream Systems Technology Center of theU.S. Forest Service.

Related Web Site: Johns Hopkins Department of Geography and Environmental Engineering -- http://www.jhu.edu:80/~dogee/


Story Source:

The above story is based on materials provided by Johns Hopkins University. Note: Materials may be edited for content and length.


Cite This Page:

Johns Hopkins University. "Sand In Sediment Can Predict River Damage." ScienceDaily. ScienceDaily, 17 April 1998. <www.sciencedaily.com/releases/1998/04/980417114343.htm>.
Johns Hopkins University. (1998, April 17). Sand In Sediment Can Predict River Damage. ScienceDaily. Retrieved September 19, 2014 from www.sciencedaily.com/releases/1998/04/980417114343.htm
Johns Hopkins University. "Sand In Sediment Can Predict River Damage." ScienceDaily. www.sciencedaily.com/releases/1998/04/980417114343.htm (accessed September 19, 2014).

Share This



More Earth & Climate News

Friday, September 19, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Wildfires in CA Burn Forest Asunder

Raw: Wildfires in CA Burn Forest Asunder

AP (Sep. 18, 2014) An out-of-control Northern California wildfire has nearly 2,800 people from their homes as it continues to grow, authorities said Thursday. Authorities said a man has been arrested on suspicion of arson for starting the fire on Saturday. (Sept. 18) Video provided by AP
Powered by NewsLook.com
Raw: Elephant Undergoes Surgery in Tbilisi Zoo

Raw: Elephant Undergoes Surgery in Tbilisi Zoo

AP (Sep. 18, 2014) Grand the elephant has successfully undergone surgery to remove a portion of infected tusk at Tbilisi Zoo in Georgia. British veterinary surgeons used an electric drill to extract the infected piece. (Sept. 18) Video provided by AP
Powered by NewsLook.com
Raw: Scientists Examine Colossal Squid

Raw: Scientists Examine Colossal Squid

AP (Sep. 16, 2014) Squid experts in New Zealand thawed and examined an unusual catch on Tuesday: a colossal squid. It was captured in Antarctica's remote Ross Sea in December last year and has been frozen for eight months. (Sept. 16) Video provided by AP
Powered by NewsLook.com
Man Floats for 31 Hours in Gulf Waters

Man Floats for 31 Hours in Gulf Waters

AP (Sep. 16, 2014) A Texas man is lucky to be alive after he and three others floated for more than a day in the Gulf of Mexico when their boat sank during a fishing trip. (Sept. 16) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins