Mar 3
2010

I just got word yesterday that I am to present at the 2010 WRRI Annual Conference at the McKimmon Center.  I am to present at session 4B: Stormwater Management II on Wednesday, March 31st. The presentation will be entitled “A Comparison of Methods for Determining Peak Discharge in Small Watersheds at Selected USGS-gaged Locations: An Evaluation of the NCDOT Method”. The abstract is as follows:

The North Carolina Department of Transportation (NCDOT) uses a method for determining peak discharges in small watersheds (< 1 mi2) that is used nowhere else. The method involves the use of a series of charts that the NCDOT published in January 1973. The origins of the charts appear to be unknown (Genereaux 2002) and the accuracy relatively untested. The author became aware of these charts when a former colleague was in a dispute regarding the design of a culvert. He had sized it using a peak flow developed using the Hydrologic Engineering Center – Hydrologic Modeling System (HEC-HMS) and Soil Conservation Service (SCS) methods while the roadway designer had found that the culvert could be reduced in size and expense if one were to use the NCDOT charts instead, which gave a lower flow rate. The incident highlighted the need to understand the strengths and weaknesses of a particular hydrologic method in order to determine the appropriateness of its use.

In this presentation, a comparison is to be made between the NCDOT method, the Rational method, and the use of U.S. Geological Survey (USGS) regression equations in determining the peak discharges for the 5, 10, 25, and 100-year events. These discharges are to be determined at locations, both urban and rural, that have been previously gaged by the USGS and used for development in their regression equations. Discharge estimates are to be made using data available from the USGS reports and National Oceanic and Atmospheric Administration (NOAA) Atlas 14. These estimates are to be compared with those developed by USGS using statistical analysis of the gage data that was collected at each location. By comparison of these various estimates, it is hoped to demonstrate when each method may reasonably be used, which method is preferable, and what kind of accuracy can be expected.

Update: The presentation can be found here: 2010 WRRI Presentation.

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Dec 2
2009

NCSU BAEThe North Carolina Department of Transportation (NCDOT) requires that those involved in the preparation and implementation of Erosion and Sediment Control plans be certified.  One can either be a Certified Professional in Erosion Sediment Control (CPESC) or Certified Professional in Storm Water Quality (CPSWQ), or one can be certified by NCDOT.  The Biological and Agricultural Engineering (BAE) department at NC State University is in charge of the certification program.  There are different levels and related workshops at which one can be certified.  Tuesday, I attended the Level IIIa workshop, which is said to apply to “E&SC/Stormwater plan designer(s)”.  There is a test at the end to ensure the competency of certificate holders.  The results of my test have yet to be announced.

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Nov 13
2009

SWATSWAT is a hydrologic model developed by the USDA Agricultural Research Station in Temple, Texas in cooperation with Texas A&M University.  Unlike most hydrologic models, SWAT models not only the movement of water, but movement of nutrients as well.  As a result, it is a tool widely used to model watershed non-point sources for their contribution to water quality.

The NC Cooperative Extension Service has arranged for the SWAT team to come to North Carolina in order to hold training sessions.  There is an introductory course to be held at NC A&T University in Winston-Salem on Monday, November 16th and Tuesday, November 17th.  I will be attending this session.  Advanced training is to be offered at NC State University on Thursday, November 19th and Friday, November 20th.

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Oct 15
2009

Raleigh News & ObserverHydropower is coming to the Triangle.  The Raleigh News & Observer is reporting that Jordan and Falls Lakes, the area’s primary sources of drinking water, are going to be retrofitted for hydroelectric power generation.  They should generate enough power for 1,700 and 1,200 homes, respectively.  The two projects will contribute to the 12.5% renewable power generation mandate for the year 2021.

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Oct 2
2009

Philly.comThe Philadelphia Inquirer is reporting that their fair city is implementing a novel strategy to reduce their problems with combined sewer overflows.  Instead of making the pipes and wastewater plants larger to handle the stormwater runoff, they are retrofitting Low Impact Development (LID) practices to reduce the runoff in developed areas.  There are to be widespread installations of bioretention facilities, permeable pavement, green roofs, and other technologies.  The plan will cost $1.6 billion, but it should end up saving money in the end.

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Oct 2
2009

Science Friday“Meandering rivers are common on Earth and other planetary surfaces, yet the conditions necessary to maintain meandering channels are unclear. As a consequence, self – maintaining meandering channels with cutoffs have not been reproduced in the laboratory…” until now.  Science Friday, a radio show on NPR, has just posted the following video of the first such model, which has been developed by UC Berkeley researchers.

“Experimental channels <like the one in the video above> are needed to explore mechanisms controlling migration rate, sinuosity, floodplain formation, and planform morphodynamics and to test theories for wavelength and bend propagation. Here we report an experiment in which meandering with near-constant width was maintained during repeated cutoff and regeneration of meander bends. We found that elevated bank strength (provided by alfalfa sprouts) relative to the cohesionless bed material and the blocking of troughs (chutes) in the lee of point bars via suspended sediment deposition were the necessary ingredients to successful meandering. Varying flood discharge was not necessary. Scaling analysis shows that the experimental meander migration was fast compared to most natural channels. This high migration rate caused nearly all of the bedload sediment to exchange laterally, such that bar growth was primarily dependent on bank sediment supplied from upstream lateral migration. The high migration rate may have contributed to the relatively low sinuosity of 1.19, and this suggests that to obtain much higher sinuosity experiments at this scale may have to be conducted for several years. Although patience is required to evolve them, these experimental channels offer the opportunity to explore several fundamental issues about river morphodynamics. Our results also suggest that sand supply may be an essential control in restoring self-maintaining, actively shifting gravel-bedded meanders.”

For the complete research article, see the Proceedings of the National Academy of Sciences.

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Aug 16
2009

I have recently had the opportunity to extend my modeling capabilities by learning SWMM5.  The training that I went through was a web-based course offered by Computational Hydraulics International (CHI), who offers their own SWMM software toolset that goes by the name of PCSWMM.  The training included the following SWMM capabilities and uses:

-Hydrologic routing using RADAR, rain gages, or synthetic events.

-Steady state and dynamic  hydraulic modeling of piped and open channel networks.

-Event-based and continuous modeling.

-Detention pond design.

-Land use – based water quality modeling and evaluation of best management practices (BMPs).

-Sanitary sewer dry weather flow (DWF) and rainfall derived inflow and infiltration (RDII).

-Sensitivity, calibration, and error analysis.

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Jul 27
2009

(Yonkers Historical Society) Yonkers, N.Y., diverted the Saw Mill River through a giant underground flume in the 1920s. Now, inspired by other cities’ efforts to “daylight” such waterways, Yonkers is trying to unbury the river and create a greenway along its banks.

(Yonkers Historical Society) Yonkers, N.Y., diverted the Saw Mill River through a giant underground flume in the 1920s. Now, inspired by other cities’ efforts to “daylight” such waterways, Yonkers is trying to unbury the river and create a greenway along its banks.

The New York Times has a story about the popularity of restoring forgotten urban streams.  These streams are forgotten because they have been piped and paved over, making them seem to be just another part of the storm drainage system.  This was often done to hide the pollution that ran through urban streams prior to the various waste treatment measures that have become widespread.  Restoration of these streams has become a worldwide phenomenon involving reaches in such varied locations as Seoul, New York, London, Los Angeles, San Antonio, and Vancouver.  One might even count Rocky Branch, which runs through North Carolina State University and highlights the work of the Biological and Agricultural Engineering Department.

There are various reasons for this movement.  The first is to bring a bit of nature to the city much as one might do with a park.  It makes the city a friendlier place that attracts more visitors and provides a place for recreation.  However, the reasons for restoration go deeper than that.  For example, streams provide habitat.  The streams in Vancouver used to provide spawning grounds for salmon.  By providing habitat, we improve and augment the food chain, which will ultimately improve and augment our own food.  Another example is the cleaning and filtering of runoff that is performed by floodplains.  Many of the elements found in stormwater runoff are either themselves health hazards or are nutrients in such over-supply that can cause microbes to run wild; in turn causing their own problems.  By removing these elements, the floodplain protects the stream habitat and downstream water supplies.  Ultimately, we are all connected to and use these streams: to bathe in, drink from, and grow food (in the wild or via agriculture).  It is heartening that so many places have seen the importance of using them wisely.

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Jul 24
2009

The New York TimesAccording to the New York Times, the White House Council on Environmental Quality (CEQ) is drafting new federal floodplain rules to be mandated by Executive Order.  These rules are to be followed by the federal government and likely by anyone using federal money for a project.  It seems that the federal government, like state departments of transportation, has been having trouble following the rules put forth by the FEMA National Flood Insurance Program (NFIP) and the White House would like have it lead by example.  For this reason, these proposed rules are likely to exceed the minimums mandated by the NFIP.  For example, critical infrastructure is not to be located in the 500-year floodplain unless no alternative is available.  If development does occur in the 100-year floodplain, it is to occur in consultation with state and local officials; thus making it follow their rules should they prove more strict.

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Jul 2
2009

And now for some local news.  The main source of drinking water in Raleigh, Falls Lake, has had some problems with nutrient levels and algal blooms.  The Neuse River, on which Falls Lake is located, already has a set of rules to regulate nutrient levels in stormwater runoff.  However, due to the sensitivity of the problems at Falls Lake, a combination of state and local officials in Wake County are pushing a plan for a speedier cleanup of the lake through the State Legislature.  This has great potential to affect Durham County, however, as much of the pollution appears to originate there.  The likely result would be an accelerated and expanded plan of retrofits to existing development to treat stormwater runoff.  It is also a potential double whammy for Durham too, as Jordan Lake, to its south, is currently undergoing development of a similar plan.  The difference for Durham, however, is that it uses Jordan Lake as a drinking water source.

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