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RE: AI-GEOSTATS: sampling strategy

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  • Myers, Jeff
    Veerle - Over the past few years, Rocky Flats Environmental Technology Site (RFETS) in Colorado has performed a similar study as part of the Actinide Migration
    Message 1 of 2 , Feb 13, 2002
      Veerle -

      Over the past few years, Rocky Flats Environmental Technology Site (RFETS)
      in Colorado has performed a similar study as part of the Actinide Migration
      Evaluation (AME). They are concerned about actinides (plutonium and
      americium) being eroded from surface soils and inpacting surface waters.
      The ability to predict sedimentation is a function of many items, not just
      the number and placement of samples. Also important are the number of
      rainfall events per year, how early in the spring the occur, their
      intensity, duration, and spacing, the particle size fractions in the soils,
      soil type, hydraulic conductivity, vegetation cover, rill and interrill
      hillslope flow, and the presence of unpaved roadways, just to name a few.
      We used a four-fold modeling system to estimate actinide concentrations in
      surface runoff: Geostatistical, GIS, Hillslope erosion, and Stream Channel
      sediment transport. As a result of the AME, we were able to produce maps
      showing areas of erosion and sedimentation across the site.

      I'm afraid there isn't a real simple answer to your question. For example,
      certain storm events will cause more sedimentation in some locations than in
      others. Small storms may cause sedimentation to occur in some areas that
      will lateer be eroded by a larger storm event. The number of samples will
      also be related to the complexity of the topography and the complexity of
      the stream network. The AME report was available electonically before
      September 11, 2001, but the RFETS website where it was located has been down
      since that time. If it comes back up, I will let you know.

      Jeff Myers
      Fellow Engineer
      Westinghouse Safety Management Solutions
      2131 S. Centennial Ave., SE
      Aiken, SC 29803
      803.502.9747 (direct)
      803.502.9767 (main)
      803.502.2747 (fax)
      803.221.1141 (cell)
      email: jeff.myers@...
      website: http://www.gemdqos.com


      -----Original Message-----
      From: Veerle Huvenne [mailto:veerle.huvenne@...]
      Sent: Tuesday, February 12, 2002 9:51 AM
      To: ai-geostats@...; Geert.Moerkerke@...
      Subject: AI-GEOSTATS: sampling strategy



      Hello Ai-geostats list members,

      A collegue of mine has the following question concerning sampling
      strategy :
      Given : a test site at which the effect of sedimentation/erosion has to
      be checked regularly (say every year). To start off with, the topography
      of the area is known. The first year the elevation is measured in a set
      of discrete points (say some 10 to 15 locations). From this one can
      gather already some information as to where there has been sedimentation
      and erosion. The following years, measurements are planned at the same
      locations. However, now comes the question :
      is there any rule of thumb, theory, calculation,... which allows to
      decide if more or less samples/measurements are necessary to achieve a
      certain precision in the mapping of erosion/sedimentation, given the
      information which can be derived from the measurements taken in the
      first year?
      If it is needed to plan more sample points, where should they be placed?
      In the areas of highest sedimentation/erosion? Or is it better to just
      choose a denser sampling grid?

      Has anybody any information on this? I know it's always difficult to
      plan a sampling design because one does not know what one will find in
      the test site, but this time there is some preliminary information
      already due to the measurements made during the first year. It seems to
      me this might change the way of looking at the problem. Or not?

      Looking forward to your answers, and thanks for your help

      Veerle

      --
      Veerle Huvenne
      Renard Centre of Marine Geology
      University of Ghent

      Krijgslaan 281, S8
      9000 Gent, Belgium
      +32/9/264.45.84



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