Ground-penetrating radar monitoring of fast subsurface processes

Geophysics ◽  
2020 ◽  
Vol 85 (3) ◽  
pp. A19-A23 ◽  
Author(s):  
Niklas Allroggen ◽  
Daniel Beiter ◽  
Jens Tronicke
Keyword(s):  
Ground Penetrating Radar ◽  
Preferential Flow ◽  
Temporal Dynamics ◽  
Time Lapse ◽  
Monitoring Methods ◽  
Attribute Analysis ◽  
Accessible Information ◽  
Spatial And Temporal Dynamics ◽  
Flow Processes ◽  
Ground Penetrating

Earth and environmental sciences rely on detailed information about subsurface processes. Whereas geophysical techniques typically provide highly resolved spatial images, monitoring subsurface processes is often associated with enormous effort and, therefore, is usually limited to point information in time or space. Thus, the development of spatial and temporal continuous field monitoring methods is a major challenge for the understanding of subsurface processes. We have developed a novel method for ground-penetrating-radar (GPR) reflection monitoring of subsurface flow processes under unsaturated conditions and applied it to a hydrological infiltration experiment performed across a periglacial slope deposit in northwest Luxembourg. Our approach relies on a spatial and temporal quasicontinuous data recording and processing, followed by an attribute analysis based on analyzing differences between individual time steps. The results demonstrate the ability of time-lapse GPR monitoring to visualize the spatial and temporal dynamics of preferential flow processes with a spatial resolution in the order of a few decimeters and temporal resolution in the order of a few minutes. We observe excellent agreement with water table information originating from different boreholes. This demonstrates the potential of surface-based GPR reflection monitoring to observe the spatiotemporal dynamics of water movements in the subsurface. It provides valuable, and so far not accessible, information for example in the field of hydrology and pedology that allows studying the actual subsurface processes rather than deducing them from point information.

scholarly journals Detecting infiltrated water and preferential flow pathways through time-lapse ground-penetrating radar surveys

2020 ◽  
Vol 726 ◽  
pp. 138511 ◽  
Author(s):  
Simone Di Prima ◽  
Thierry Winiarski ◽  
Rafael Angulo-Jaramillo ◽  
Ryan D. Stewart ◽  
Mirko Castellini ◽  
...  
Keyword(s):  
Ground Penetrating Radar ◽  
Preferential Flow ◽  
Time Lapse ◽  
Flow Pathways ◽  
Preferential Flow Pathways ◽  
Ground Penetrating

Ground-penetrating radar surveys for the detection of preferential flow into soils

2020 ◽  
Author(s):  
Simone Di Prima ◽  
Thierry Winiarski ◽  
Rafael Angulo-Jaramillo ◽  
Ryan D. Stewart ◽  
Mirko Castellini ◽  
...  
Keyword(s):  
Ground Penetrating Radar ◽  
Preferential Flow ◽  
Three Dimensional ◽  
Time Lapse ◽  
Water Infiltration ◽  
Single Ring ◽  
Before And After ◽  
Infiltration Tests ◽  
Ground Penetrating ◽  
Preferential Flows

<p>Preferential flow is more the rule than the exception, in particular during water infiltration experiments. In this study, we demonstrate the potential of GPR monitoring to detect preferential flows during water infiltration. We monitored time-lapse ground penetrating radar (GPR) surveys in the vicinity of single-ring infiltration experiments and created a three-dimensional (3D) representation of infiltrated water below the devices. For that purpose, radargrams were constructed from GPR transects conducted over two grids (1 m × 1 m) before and after the infiltration tests. The obtained signal was represented in 3D and a threshold was chosen to part the domain into wetted and non-wetted zones, allowing the determination of the infiltration bulb. That methodology was used to detect the infiltration below the devices and clearly pointed at nonuniform flows in correspondence with the heterogeneous soil structures. The protocol presented in this study represents a practical and valuable tool for detecting preferential flows at the scale of a single ring infiltration experiment.</p>

Attribute-based analysis of time-lapse ground-penetrating radar data

Geophysics ◽  
2016 ◽  
Vol 81 (1) ◽  
pp. H1-H8 ◽  
Author(s):  
Niklas Allroggen ◽  
Jens Tronicke
Keyword(s):  
Ground Penetrating Radar ◽  
Preferential Flow ◽  
Synthetic Data ◽  
Structural Similarity ◽  
Time Lapse ◽  
Radar Data ◽  
Hydrological Processes ◽  
Time Shift ◽  
Noisy Input ◽  
Ground Penetrating

Analysis of time-lapse ground-penetrating radar (GPR) data can provide information regarding subsurface hydrological processes, such as preferential flow. However, the analysis of time-lapse data is often limited by data quality; for example, for noisy input data, the interpretation of difference images is often difficult. Motivated by modern image-processing tools, we have developed two robust GPR attributes, which allow us to distinguish amplitude (contrast similarity) and time-shift (structural similarity) variations related to differences between individual time-lapse GPR data sets. We tested and evaluated our attributes using synthetic data of different complexity. Afterward, we applied them to a field data example, in which subsurface flow was induced by an artificial rainfall event. For all examples, we identified our structural similarity attribute to be a robust measure for highlighting time-lapse changes also in data with low signal-to-noise ratios. We determined that our new attribute-based workflow is a promising tool to analyze time-lapse GPR data, especially for imaging subsurface hydrological processes.

Detecting stemflow-induced preferential flow pathways through time-lapse ground-penetrating radar surveys

2021 ◽  
Author(s):  
Ludmila Roder ◽  
Simone Di Prima ◽  
Sergio Campus ◽  
Filippo Giadrossich ◽  
Ryan D. Stewart ◽  
...  
Keyword(s):  
Ground Penetrating Radar ◽  
Preferential Flow ◽  
Overland Flow ◽  
Root Systems ◽  
Time Lapse ◽  
Water Infiltration ◽  
Blue Dye ◽  
Horizontal Distance ◽  
Tree Trunk ◽  
Ground Penetrating

<p>Research over the past several decades has shown that preferential flow is more the rule than the exception. However, our collective understanding of preferential flow processes has been limited by a lack of suitable methods to detect and visualize the initiation and evolution of non-uniform wetting at high spatial and temporal resolutions, particularly in real-world settings. In this study, we investigate water infiltration initiation by tree trunk and root systems. We carried out time-lapse ground penetrating radar (GPR) surveys in conjunction with a simulated stemflow event to provide evidence of root-induced preferential flow and generate a three-dimensional representation of the wetted zone.</p><p>We established a survey grid (3.5 m × 5 m, with a local slope of 10.3°), consisting of ten horizontal and thirteen vertical parallel survey lines with 0.5 m intervals between them. The horizontal lines were downslope-oriented. The grid was placed around a Quercus suber L. We collected a total of 46 (2 GPR surveys × 23 survey lines) radargrams using an IDS (Ingegneria Dei Sistemi S.p.A.) Ris Hi Mod v. 1.0 system with a 900-MHz antenna mounted on a GPR cart. Two grid GPR surveys were carried out before and after the artificial stemflow experiment. In the experiment, we applied 100 L of brilliant blue dye (E133) solution on the tree trunk. The stemflow volume of 100 L corresponded to 63.2 mm of incident precipitation, considering a crown projected area of 201 m<sup>2</sup> and a 1.3% conversion rate of rainfall to stemflow. Trench profiles were carefully excavated with hand tools to remove soil and detect both root location and size and areas of infiltration and preferential pathways on the soil profile.</p><p>The majority (84.4%) of artificially applied stemflow infiltrated into the soil, while the remaining 15.6% generated overland flow, which was collected by a small v-shaped plastic channel placed into a groove previously scraped on the downhill side of the tree. The 3D diagram clearly demarcated the dimension and shape of the wetted zone, thus providing evidence of root-induced preferential flow along coarse roots. The wetted zone extended downslope up to a horizontal distance of 3 m from the trunk and down to a depth of approximately 0.7 m. Put all together, this study shows the importance of accounting for plant and trees trunk and root systems when quantifying infiltration.</p>

scholarly journals In situ investigation of rapid subsurface flow: Temporal dynamics and catchment-scale implication

2016 ◽  
Author(s):  
Lisa Angermann ◽  
Conrad Jackisch ◽  
Niklas Allroggen ◽  
Matthias Sprenger ◽  
Erwin Zehe ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Preferential Flow ◽  
Temporal Dynamics ◽  
Subsurface Flow ◽  
Time Lapse ◽  
Small Scale ◽  
Response Behavior ◽  
In Situ Investigation ◽  
Flow Processes ◽  
Hillslope Scale

Abstract. Preferential flow is omnipresent in natural systems. It links multiple scales from single pores to entire hillslopes and potentially influences the discharge dynamics of a catchment. However, there is still a lack of appropriate monitoring techniques and thus, process understanding. In this study, a promising combination of 2D time-lapse ground-penetrating radar (GPR) and soil moisture monitoring was used to observe preferential flow processes in highly structured soils during a hillslope-scale irrigation experiment. The 2D time-lapse GPR data were interpreted using structural similarity attributes, highlighting changes between individual time-lapse measurements. These changes are related to soil moisture variations in the subsurface. In combination with direct measurements of soil moisture, the spatial and temporal characteristics of the resulting patterns can give evidence about subsurface flow processes. The response dynamics at the hillslope were compared to the runoff response behavior of the headwater catchment. The experiment revealed a fast establishment of hillslope-scale connectivity despite unsaturated conditions, with high response velocities of up to 10−3 m s−1 or faster, and a high portion of mobile water. These processes substantially impact the overall catchment response behavior. While the presented approach is a good way to observe the temporal dynamics and general patterns, the spatial characteristics of small-scale preferential flow path could not be fully resolved.

scholarly journals Form and function in hillslope hydrology: characterization of subsurface flow based on response observations

2017 ◽  
Vol 21 (7) ◽  
pp. 3727-3748 ◽  
Author(s):  
Lisa Angermann ◽  
Conrad Jackisch ◽  
Niklas Allroggen ◽  
Matthias Sprenger ◽  
Erwin Zehe ◽  
...  
Keyword(s):  
Preferential Flow ◽  
Explanatory Power ◽  
Subsurface Flow ◽  
Time Lapse ◽  
Storm Event ◽  
Monitoring Methods ◽  
Catchment Scale ◽  
Flow Paths ◽  
Form And Function ◽  
And Function

Abstract. The phrase form and function was established in architecture and biology and refers to the idea that form and functionality are closely correlated, influence each other, and co-evolve. We suggest transferring this idea to hydrological systems to separate and analyze their two main characteristics: their form, which is equivalent to the spatial structure and static properties, and their function, equivalent to internal responses and hydrological behavior. While this approach is not particularly new to hydrological field research, we want to employ this concept to explicitly pursue the question of what information is most advantageous to understand a hydrological system. We applied this concept to subsurface flow within a hillslope, with a methodological focus on function: we conducted observations during a natural storm event and followed this with a hillslope-scale irrigation experiment. The results are used to infer hydrological processes of the monitored system. Based on these findings, the explanatory power and conclusiveness of the data are discussed. The measurements included basic hydrological monitoring methods, like piezometers, soil moisture, and discharge measurements. These were accompanied by isotope sampling and a novel application of 2-D time-lapse GPR (ground-penetrating radar). The main finding regarding the processes in the hillslope was that preferential flow paths were established quickly, despite unsaturated conditions. These flow paths also caused a detectable signal in the catchment response following a natural rainfall event, showing that these processes are relevant also at the catchment scale. Thus, we conclude that response observations (dynamics and patterns, i.e., indicators of function) were well suited to describing processes at the observational scale. Especially the use of 2-D time-lapse GPR measurements, providing detailed subsurface response patterns, as well as the combination of stream-centered and hillslope-centered approaches, allowed us to link processes and put them in a larger context. Transfer to other scales beyond observational scale and generalizations, however, rely on the knowledge of structures (form) and remain speculative. The complementary approach with a methodological focus on form (i.e., structure exploration) is presented and discussed in the companion paper by Jackisch et al.(2017).

Ground Penetrating Radar (GPR) attribute analysis for archaeological prospection

2013 ◽  
Vol 97 ◽  
pp. 107-117 ◽  
Author(s):  
Wenke Zhao ◽  
Emanuele Forte ◽  
Michele Pipan ◽  
Gang Tian
Keyword(s):  
Ground Penetrating Radar ◽  
Archaeological Prospection ◽  
Attribute Analysis ◽  
Ground Penetrating

scholarly journals Quantitative high-resolution observations of soil water dynamics in a complicated architecture using time-lapse ground-penetrating radar

2015 ◽  
Vol 19 (3) ◽  
pp. 1125-1139 ◽  
Author(s):  
P. Klenk ◽  
S. Jaumann ◽  
K. Roth
Keyword(s):  
High Resolution ◽  
Water Content ◽  
Soil Water ◽  
Ground Penetrating Radar ◽  
Time Lapse ◽  
Test Site ◽  
Water Dynamics ◽  
Soil Water Dynamics ◽  
Capillary Fringe ◽  
Ground Penetrating

Abstract. High-resolution time-lapse ground-penetrating radar (GPR) observations of advancing and retreating water tables can yield a wealth of information about near-surface water content dynamics. In this study, we present and analyze a series of imbibition, drainage and infiltration experiments that have been carried out at our artificial ASSESS test site and observed with surface-based GPR. The test site features a complicated but known subsurface architecture constructed with three different kinds of sand. It allows the study of soil water dynamics with GPR under a wide range of different conditions. Here, we assess in particular (i) the feasibility of monitoring the dynamic shape of the capillary fringe reflection and (ii) the relative precision of monitoring soil water dynamics averaged over the whole vertical extent by evaluating the bottom reflection. The phenomenology of the GPR response of a dynamically changing capillary fringe is developed from a soil physical point of view. We then explain experimentally observed phenomena based on numerical simulations of both the water content dynamics and the expected GPR response.

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