Featured Research

from universities, journals, and other organizations

Sediment Prediction Tools Off The Mark

Date:
February 5, 2008
Source:
Smithsonian
Summary:
A recent study led by a Smithsonian ecologist suggests it is time for a change in at least one area of watershed management. She has been examining the tools scientists and managers use to predict how much sediment runs into the Chesapeake Bay, and by her account, they are way off the mark. The new study compared actual measurement of sediments in more than 100 streams in the Chesapeake watershed with predictions from several of the most up-to-date models. All the models failed completely to identify streams with high sediment levels.

The water appears murky in this photo of Muddy Branch Creek, due to sediment after heavy rains. Muddy Branch Creek is within the Chesapeake Bay watershed. Sediment running into the bay reduces light, suffocates underwater organisms and is a significant source of phosphorous, a nutrient that essentially fertilizes the water promoting algal blooms and many other problems in the bay.
Credit: Michele Hogan

A recent study led by Smithsonian ecologist Kathy Boomer suggests it is time for a change in at least one area of watershed management. Boomer has been examining the tools scientists and managers use to predict how much sediment runs into the Chesapeake Bay, and by her account, they are way off the mark.

Sediment running into the bay reduces light, suffocates underwater organisms and is a significant source of phosphorus, a nutrient that essentially fertilizes the water promoting algal blooms and many other problems in the bay.

The study, co-authored by SERC ecological modeler Donald Weller and ecologist Thomas Jordan, appears in the January/February issue of the Journal of Environmental Quality. "Cities and counties are under increasing pressure to meet total maximum daily loads set by state and federal agencies and to understand where sediments come from," she said. "So we tested the tools most widely used now to predict sediment delivery."

Her work has led to a new tactic. "We're moving away from focusing on upland erosion and looking more at what happens near streams and in streams during events with high levels of stream sediments."

The new study compared actual measurement of sediments in more than 100 streams in the Chesapeake watershed with predictions from several of the most up-to-date models. All the models failed completely to identify streams with high sediment levels.

"There was no correlation at all between the model predictions and the measurements," said Boomer. The study is among the first to directly compare predictions of the widely used models with actual observations of sediments in a large number of streams.

The problem, she said, is that the most widely used models all begin with the same tool, the Universal Sediment Loss Equation. The USLE estimates erosion from five factors: topography, soil erodibility, annual average rainfall amount and intensity, land cover, and land management practices. Boomer emphasized that the USLE was developed to help farmers limit topsoil loss from individual fields rather than to predict sediment delivery from complex watersheds to streams.

As often applied, the USLE gives an average annual erosion rate for the whole watershed draining into a stream. But not all of the eroded soil makes it into the water, so the estimates do not translate directly into sediment delivery rates. To account for the discrepancy, different models incorporate a wide variety of adjustments. According to Boomer, the adjusted models still do not work, partly because erosion rate is not the best information to start with.

During the study, Boomer and colleagues Weller and Jordan compared erosion rates and sediment yields estimated from regional application of the USLE, the automated Revised-USLE, and five widely used sediment delivery ratio algorithms to measured annual average sediment delivery in 78 catchments of the Chesapeake Bay watershed.

"We did the same comparisons for an independent set of 23 watersheds monitored by the U.S. Geological Society," Boomer said.

Sediment delivery predictions, which were highly correlated with USLE erosion predictions, exceeded observed sediment yields by more than 100 percent. The RUSLE2 erosion estimates also were highly correlated with the USLE predictions, indicating that the method of implementing the USLE model did not greatly change the results.

"Sediment delivery is largely associated with specific rain events and stream bank erosion," she said. "So, USLE-based models that emphasize long-term annual average erosion from uplands provide limited information to land managers."

With a new focus on what is happening in and near the streams themselves, Boomer and her colleagues hope to develop more reliable tools to predict sediment running into Chesapeake Bay--tools that can be used in other lakes and estuaries as well.


Story Source:

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


Cite This Page:

Smithsonian. "Sediment Prediction Tools Off The Mark." ScienceDaily. ScienceDaily, 5 February 2008. <www.sciencedaily.com/releases/2008/01/080129160722.htm>.
Smithsonian. (2008, February 5). Sediment Prediction Tools Off The Mark. ScienceDaily. Retrieved July 22, 2014 from www.sciencedaily.com/releases/2008/01/080129160722.htm
Smithsonian. "Sediment Prediction Tools Off The Mark." ScienceDaily. www.sciencedaily.com/releases/2008/01/080129160722.htm (accessed July 22, 2014).

Share This




More Earth & Climate News

Tuesday, July 22, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

New Orleans Plans to Recycle Cigarette Butts

New Orleans Plans to Recycle Cigarette Butts

AP (July 21, 2014) New Orleans is the first U.S. city to participate in a large-scale recycling effort for cigarette butts. The city is rolling out dozens of containers for smokers to use when they discard their butts. (July 21) Video provided by AP
Powered by NewsLook.com
Shark Sightings a Big Catch for Cape Tourism

Shark Sightings a Big Catch for Cape Tourism

AP (July 21, 2014) A rise in shark sightings along the shores of Chatham, Massachusetts is driving a surge of eager vacationers to the beach town looking to catch a glimpse of a great white. (July 21) Video provided by AP
Powered by NewsLook.com
Spectacular Lightning Storm Hits London

Spectacular Lightning Storm Hits London

AFP (July 19, 2014) A spectaCular lightning storm struck the UK overnight Friday. Images of lightning strikes over the Shard and Tower Bridge in central London. Duration: 00:23 Video provided by AFP
Powered by NewsLook.com
A Centuries' Old British Tradition Is Far from a Swan Song

A Centuries' Old British Tradition Is Far from a Swan Song

AFP (July 19, 2014) As if it weren't enough that the Queen is the Sovereign of the UK and 15 other Commonwealth realms, she is also the owner of all Britain's unmarked swans. Duration: 02:18 Video provided by AFP
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