Tag Archives: sediment

New Approach to Understanding Sediment Transport in River Channels

A recent set of four related articles published in the Journal of Geophysical Research-Earth Surface takes a new approach to understanding sediment transport, a vital component to the ecological health and long-term evolution of river channels.

When you look at a river’s water surface, it is rarely smooth. Instead, you can usually see the continual churning of turbulent river flow. Sediment transport occurs as this turbulent flow disturbs sand and gravel riverbeds, and the river is flowing fast enough to move the particles downstream. The complex nature of turbulent river flow makes quantifying sediment transport a difficult task.

The new approach to understanding sediment transport developed in this study involves describing individual sediment particle motions and positions as the basis for calculating total transport amounts. High-speed videos of sand grains moving at different flow rates were analyzed to provide experimental data to compare with the new theory. A video showing digitized sand grains transported during experiments is available here. The transport of sand particles is shown by experiment results to be extremely variable in both the location and amount of sediment movement at any given flow. This variability in particle motions results from the complex interaction of turbulent flow with the riverbed.

As our understanding of sediment transport and other river processes continues to improve, so does the ability of the restoration community to provide effective, science-based solutions to degraded aquatic resources, increasing the likelihood of long-term success of restoration projects.

Author John Roseberry, an Environmental Engineer at Trout Headwaters, Inc. and Ph.D. candidate at Vanderbilt University, was lead author of the second article in the series of four from this study. 

Links:

Roseberry et al, 2012: http://www.agu.org/pubs/crossref/2012/2012JF002353.shtml

Furbish et al, 2012a:  http://www.agu.org/pubs/crossref/2012/2012JF002352.shtml

 

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Damaging Environmental Scenarios Loom as Sandy Approaches the East Coast

The Washington Post reported today on the potential environmental threats to the Chesapeake Bay posed by Hurricane Sandy. “More than a hundred million tons of dirty sediment mixed with tree limbs and junk float behind the Conowingo Dam, and Hurricane Sandy, a giant faucet nicknamed “Frankenstorm,” could send it pouring into the Chesapeake Bay,” says the Post.

Read more: http://www.washingtonpost.com/national/health-science/sandy-poses-environmental-threat-to-chesapeake-bay/2012/10/27/64bb8630-1fb2-11e2-9cd5-b55c38388962_story.html

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Potomac River Tops the Most Endangered River List – All Rivers Need Protection

The non-profit advocacy group American Rivers is naming the Potomac the nation’s most endangered river, saying it is threatened by nutrient and sediment pollution that lowers the quality of drinking water and kills marine life.

The group’s annual report titled, “America’s Most Endangered Rivers,” notes what local friends of the Potomac have said for years: that urban development is funneling tons of polluted rainwater to the river; that chemical fertilizer and manure from farms make matters worse; and that wastewater overflowing from sewers, along with pharmaceuticals flushed down toilets, contribute to dead zones in which marine life dies and might cause fish to switch sexes. Some male fish in the river mysteriously have eggs.

The Potomac River, a large Chesapeake Bay tributary, supplanted another bay tributary (the Susquehanna River) as the Nation’s most endangered river.  How does a river that was ranked first last year, now fall off the list?  River restoration cannot be measured in a year, so it’s not that the Susquehanna is now fully restored. Heightening public awareness about the plight of all of our nation’s rivers is crucial, and the annual list is an effective marketing tool.

This year the Clean Water Act turns 40, and even in the face of severe threats to our water resources, Congress continues its attempts to roll back clean water regulations. Read more and find links about the rankings and the report:

http://www.washingtonpost.com/national/health-science/potomac-river-threatened-by-pollution-congress-new-report-says/2012/05/14/gIQAxl89PU_story.html

To learn more about American Rivers: http://www.amrivers.org/

Author Doug Pickford of Trout Headwaters, Inc. (THI), an environmental planner with 20 years of experience in the Chesapeake Bay area, follows events in the bay watershed as the tide turns from voluntary to mandatory for bay cleanup regulations and protections.   Doug’s blog series for THI will document what is likely the largest and most significant watershed clean up effort in the history of the U.S., and offer his insights into some practical ways to assist the health of this magnificent natural resource

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A Picture from Space Tells the Story of Lee’s Impact on the Chesapeake

Stream and River Restoration  Is Critical to Reducing the Impacts of Storm Events on the Chesapeake Bay Watershed

Runoff from the rainfall caused by the remnants of Tropical Storm Lee set off a deluge of sediment, trash and toxic sewer wastes in the Chesapeake Bay and its tributaries.  The satellite image below, captured by the MODIS Rapid Response Project at NASA/GSFC, is visual evidence of the daunting task that sits before environmentalists, businesses, and residents of the Chesapeake Bay watershed.  The massive, murky brown plume, clearly evident in the satellite image, is a witches brew of flotsam and sediment laden water that covers almost 50 percent of the 200-mile-long Bay. 

This toxic plume originated from the scouring effects of large volumes of water flowing across farm fields, suburban yards, and impervious surfaces (roofs and parking lots), tumbled with by-products of urban and rural development (trash, fertilizers, human and animal wastes, etc.).  Bay naturalists fear that this gigantic sediment plume will create yet another large dead zone in the Bay, imperiling already fragile oyster and mollusk populations.  

The recent efforts of the EPA to enact a Total Daily Maximum Load (TMDL) for the Bay will begin to address these problems.  The next step for local communities is to develop very specific Watershed Implementation Plans (WIPs) that will examine each and every Bay tributary to develop strategies that will lessen the impacts of storm events.

Read more about the effects of Tropical Storm Lee on the Bay at: www.washingtonpost.com/national/health-science/chesapeake-takes-a-beating-from-storm/2011/09/13/gIQAKNVaQK_story.html

Author Doug Pickford of Trout Headwaters, Inc. (THI), an environmental planner with 20 years of experience in the Chesapeake Bay area, follows events in the bay watershed as the tide turns from voluntary to mandatory for bay cleanup regulations and protections.   Doug’s blog series for THI will document what is likely the largest and most significant watershed clean up effort in the history of the U.S., and offer his insights into some practical ways to assist the health of this magnificent natural resource.

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The Chesapeake Bay Goes on A Diet – Private Landowners Should Be Prepared to Slim Down Too

Doug Pickford of Trout Headwaters, Inc. (THI), an environmental planner with 20 years of experience in the Chesapeake Bay area, will follow events in the bay watershed as the tide turns from voluntary to mandatory for bay cleanup regulations and protections.   Doug’s blog series for THI will document what is likely the largest and most significant watershed clean up effort in the history of the U.S., and offer his insights into some practical ways to assist the health of this magnificent natural resource.

Background

In December 2010, the U.S. EPA issued regulatory language that essentially requires all of the states within the Chesapeake Bay watershed to reduce the amount of pollution entering the Bay.  This Total Maximum Daily Load (TMDL) is a long-awaited step that put an end to more than 25 years of voluntary state efforts to clean up the Bay. 

After decades of missed milestones and pushed back implementation targets, the next critical date for the Chesapeake Bay TMDL is Dec. 31, 2011.  This is when the jurisdictions will have to prove they have met the goals they had agreed to back in 2009.   Environmental groups will be closely watching the EPA to see what consequences will occur should these targets go unmet. 

Important Decisions Loom for Bay Restoration Stakeholders

The sheer scale of the Chesapeake Bay Watershed, with a high population and a diverse array of stakeholders, is daunting.  As has been the case elsewhere, applying cookie-cutter solutions to stream and wetland restoration is likely to result in expensive failures.   True restoration will require careful planning, a local focus, and highly qualified practitioners to implement the kind of sustainable, meaningful stream, river and wetland restoration that can save the Bay.  

The overall goal of the Bay TMDL is to remove more than 6.67 billion pounds of sedimentation from the streams and rivers feeding the Bay.  More than 90% of this targeted sediment reduction will come from the states of Maryland (1.22 billion lbs.), Pennsylvania (2.09 billion lbs.), and Virginia (2.69 billion lbs.).  Under the current Bay TMDL, all states will have to achieve 60% of their respective reductions by 2017, and meet the final targets by 2025.

The Bay TMDL revolves around the development of Watershed Implementation Plans (WIPs), which commit each state to specific goals for reducing nitrogen, phosphorous and sediment.   It is by far the largest and most significant watershed clean up effort in the history of the U.S.(and quite possibly the world), and is already being challenged in the courts by the American Farm Bureau Federation and other agricultural interest groups.  These groups contend that the Bay initiative will be costly to landowners, and will set the precedent for implementing similar TMDL’s in other large watersheds, such as the Mississippi.

The work that needs to be done under the Bay TMDL is substantial.  Baywide, the jurisdictions will have to reduce nitrogen by 25%, phosphorus by 24% and sediment by 18%.  Over the next two years the states and the District of Columbia will be required to update their WIPs to determine how all of these goals will be met a the local level.  These plans are where the rubber meets the road, so to speak, and will be very specific in their implementation strategies.

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It Will Take a (Conservation) Village

I sit watching the brown slug of Argentina’s broad Rio de la Plata flow to the Atlantic Ocean.  Sediment roiled runoff a mile wide originating in farm fields and city streets, draining from gravel roads and cattle feedlots – all emptying into the estuary.  I studied this same phenomena in my own hemisphere during the past spring, wondering how much of the nonpoint source pollution in Montana’s Yellowstone River had been caused just within my short lifetime.   The perennial dirty brown water exacerbated by denuded riparian buffers, irrigation returns, hardened stream banks and man’s other “utilitarian” measures aimed at “taming” her.

As our world’s finite and increasingly precious freshwater resources continue to lean ever closer to the tipping point, the weight of our problems and our responsibilities becomes greater.  The need for action, for change, for repair and for restoration increases.  

When one travels along the distance of these great rivers, as I have been fortunate to do, it quickly becomes obvious that no single entity – be it a government, a landowner or a corporation –  can alter the present path of degradation.  It will truly take a village – a conservation village.         

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