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AI-GEOSTATS: sampling strategy

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  • Veerle Huvenne
    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
    Message 1 of 2 , Feb 12, 2002
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      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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    • 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 2 of 2 , Feb 13, 2002
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        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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        "unsubscribe ai-geostats" followed by "end" on the next line in the message
        body. DO NOT SEND Subscribe/Unsubscribe requests to the list
        * Support to the list is provided at http://www.ai-geostats.org

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        * As a general service to the users, please remember to post a summary of any useful responses to your questions.
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