Tag Archives: engineer

Flood Alleviation – Unpaid Engineers to Restore Floodplains

Following major floods in January 2014 Marina Pacheco, the chief executive of the UK Mammal Society, recommended that the UK Government promote beaver reintroductions as a means of reducing flood risk in the future.

“Restoring the beaver to Britain’s rivers would bring huge benefits in terms of flood alleviation. These unpaid river engineers would quickly re-establish more natural systems that retain water behind multiple small dams across tributaries and side-streams. As a consequence the severity of flooding further downstream would be greatly reduced, at no cost to the taxpayer,” wrote Pacheco.

This regulation in river flow may also help reduce flooding and bankside erosion downstream according to the biofresh blog http://biofreshblog.com/2014/04/18/beavers-ecological-stress-and-river-restoration/

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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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Engineering Cannot Save Our Rivers

We note the draft language in Montana DNRC’s 2012 Model Floodplain Ordinance requiring that “a licensed professional engineer” (P.E.) design all stream restoration and bank stabilization projects undertaken in Montana.  While engineering is an important professional discipline, the proposed rule as written would greatly diminish the vital roles played by hydrologists, fluvial geomorphologists, sedimentologists, ecologists, and the other skilled scientists in this important work.  Further, it’s very important to understand that there is no consistent requirement in a professional engineer’s academic training or in Montana’s P.E. certification criteria that would dictate the attainment of specific skills for stream bank stabilization and restoration.

Decades of misguided, hard-engineering attempts to force natural stream systems into unnatural configurations have resulted in unhealthy, armored floodplains along many of our nation’s streams, including in Montana.  History will likely describe our time as a period of human failure – the failure to understand and the failure to accommodate the most basic ecological needs and functions of our precious water resources. These waters and their floodplains serve a broad host of ecological services for humans and wildlife, providing biodiversity, aquifer recharge and carbon sequestration. Without the protection of these basic functions, we will pass to the next generation a tarnished legacy of damaged and destroyed resources.

Any successful stream restoration or bank stabilization project requires a multi-disciplinary or inter-disciplinary team of scientists and technicians to ensure success. THI would suggest that granting a design monopoly for stream bank stabilization and river restoration to engineers may simply expose many P.E.’s to increased liability due to a general lack of direct experience in these applications.

Anyone interested in the future of Montana’s Floodplains, Rivers and Wetlands should comment on Montana DNRC’s 2012 Model Floodplain Ordinance now:  Traci Sears phone: 406-444‐6654, or via email  at  tsears@mt.gov

>>Read the Montana DNRC’s 2012 Model Floodplain Ordinance http://dnrc.mt.gov/wrd/water_op/floodplain/news/draft_model_ordinance.pdf

 

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Builders, Architects, Engineers – Why Buy Credits in a Mitigation Bank?

Why buy credits in a mitigation bank instead of creating a wetland or restoring a stream on- or off-site? Purchasing credits gives the developer these major benefits:

Save time and money: The developer, after following the 404(B)(1) Guidelines to try to avoid or  minimize wetland or stream impacts, then does not have to go through the time-consuming permit approval process to create or restore a wetland, riparian buffer or stream reach.  One of the benefits described in the Federal Guidance for the Establishment, Use and Operation of Mitigation Banks is that “Use of mitigation banks may reduce permit processing times and provide more cost-effective compensatory mitigation opportunities for projects that qualify.”   Additionally, the developer may not be experienced in wetland or stream restoration, may not have the additional land required for mitigation, may not wish to encumber the mitigation property in perpetuity or other issues. For the long term, buying credits in a bank is usually less costly than “doing your own”, particularly when the cost of the additional permitting process is added to the construction task.  Mitigation requirements like easements and long-term monitoring can be time consuming activities.

Eliminates risk and responsibility: The credit transaction legally transfers all responsibility for wetland and stream mitigation to the mitigation banker.

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And purchasing credits in a mitigation bank brings one more highly significant benefit for the environment:

The mitigation bank assures that the mitigation works – and lasts.  Too often, wetlands built on-site eventually fail because the landowner does not have sufficient incentive or know how to maintain them.

Mitigation bankers assume total responsibility for the mitigation and guarantee perpetual maintenance of the bank’s environmental assets Mitigation is typically performed prior to the wetland impacts, therefore reducing or eliminating temporal loss of wetland functions.

Mitigation financial securities and conservation easements are in place prior to wetland impacts.

Information Courtesy the National Mitigation Banking Association (NMBA)

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