Form and function in hillslope hydrology: characterization of subsurface flow based on response observations
The phrase <i>form and function</i> 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 Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-07-01
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| Series: | Hydrology and Earth System Sciences |
| Online Access: | https://www.hydrol-earth-syst-sci.net/21/3727/2017/hess-21-3727-2017.pdf |
| Summary: | The phrase <i>form and function</i> 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). |
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| ISSN: | 1027-5606 1607-7938 |