Evaluation and Development of Rapid Geophysical Profiling for Canal Embankment and Levee Health Assessment and Seepage Detection.
This proposal revolves around the evaluation of frequency-domain electromagnetic (FEM) and other
geophysical techniques for rapid profiling of canal embankments and levees, motivated by the need for
more efficient/rapid means of identifying: 1) anomalous seepage, 2) voids created by animal burrowing, 3)
unauthorized or "lost" canal penetrations. Specific research questions or areas of interest by team
members include the following:
1)Can FEM profiling of canal levees (using commercially available EM systems, such as the Geonics EM31 or
EM34) serve as a rapid and effective reconnaissance tool for identification of anomalous and focused
seepage or sections of levee experiencing abnormal distributed seepage or anomalous saturation levels?
2)Can FEM profiling reliably identify possible animal burrow areas or areas with man-made canal
3) Is the effectiveness of FEM profiling diminished when systems are mounted on a
non-magnetic/non-metallic cart being towed by an ATV at some reasonable distance and speed?
4) Are manually collected data and cart-towed data consistent, and if so, what are the main logistical
concerns and technical limitations of system(s) operated in a cart-towed manner? For example, how many
miles of data coverage can be collected and evaluated in a typical day of field deployment?
5) Does FEM data correlate well with pre-established electrical resistivity values and trends, as measured
and observed in several locations during previous canal seepage investigations conducted throughout
2011 and 2012?
6) Do FEM data profiles along canal levees spatially and/or temporally correlate with other anomalous
seepage indicators, such as those obtained from airborne or satellite remote sensing data/analysis?
7) What is the target resolution of specific FEM systems ?
8) What other geophysical survey methods could effectively be used in a towed-system cconfiguration?
9) How does a towed-array survey compare to low-altitude airborne
Need and Benefit
Here in the United States alone, there are currently over 100,000 miles of levee embankments and
approximately 79,000 dams on the national inventory list. Many of these structures are reaching or have
surpassed their initial design life, where most embankment structures are over 50 years in age, and many
are greater than 80 years in age. The Homeland Security Presidential Directive of May 7th, 2007 classified
dams and levees as one of the 18 most critical infrastructure and key resource sectors, [e.g., assets,
systems, and networks, whether physical or virtual, so vital to the United States that their incapacitation or
destruction would have a debilitating effect on security, national economic security, public health or safety,
or any combination thereof] (Hickey, 2012). As a result, current efforts are being made at the federal level
to update the US inventory of earthen dams and levees (EDLs), and to prioritize further detailed assessment
of high-risk and poorly performing structures or segments of structures that exhibit states of poor health.
This later effort is where this proposed research fits in. The proposed research will help to improve specific
geophysical tools for rapid and proactive characterization of canal levee and embankment structures, and
for quick reconnaissance surveys to be conducted along extensive segments of canal levees and
embankments. These reconnaissance data will allow for a more informed, focused and guided approach to
prioritizing more detailed field investigations and/or repair efforts in problematic areas experiencing
abnormal seepage or behavior. These data will provide additional and valuable information that can be
considered alongside regular visual inspections information when making decisions on appropriate
follow-up activities. Comparison of these data with visual inspection reports could provide a useful way to
cross-validate both approaches to levee and embankment inspections for seepage or poor structural health
This approach to identifying abnormal seepage or saturation levels within canal levees and embankments
(based on electrical conductivity signatures/anomalies/trends) will help save a considerable amount of
money being spent on geophysical investigation efforts. This savings would be achieved by avoiding
unnecessarily expensive and time consuming electrical resistivity tomography (ERT) profiling surveys
currently being used as a first-round geophysical investigation tool for delineating lateral changes in
electrical conductivity that is interpreted to be associated with seepage. The current approach of using ERT
profiling as the go-to tool for this and related efforts, is analogous to drilling hundreds of exploration
wells in order to delineate the boundaries of an oil reservoir. If the boundaries can be found in a quicker
and cheaper fashion, the subsequent use of more detailed and more expensive surveys (e.g., 2D or 3D or
4D ERT surveys, other geophysical surveys, cone penetrometer, etc. ) can be better focused, optimized and
will ultimately provide a better value of information to land owners, irrigation districts, flood control
districts, municipalities, the Bureau, and decision makers alike.
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