Form and function in hillslope hydrology: Characterization of subsurface ow based on response observations

Lisa Angermann (Corresponding Author), Conrad Jackisch, Niklas Allroggen, Matthias Sprenger, Erwin Zehe, Jens Tronicke, Markus Weiler, Theresa Blume

Research output: Contribution to journalArticlepeer-review

47 Citations (Scopus)
146 Downloads (Pure)


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).
Original languageEnglish
Pages (from-to)3727-3748
Number of pages22
JournalHydrology and Earth System Sciences
Issue number7
Publication statusPublished - 21 Jul 2017

Bibliographical note

Acknowledgements. We are grateful to Marcel Delock, Lisei Köhn,
and Marvin Reich for their support during fieldwork, as well as
Markus Morgner and Jean Francois Iffly for technical support,
Britta Kattenstroth for hydrometeorological data acquisition and
isotope sampling, and Barbara Herbstritt and Begoña Lorente
Sistiaga for laboratory work. Laurent Pfister and Jean-Francois
Iffly from the Luxembourg Institute of Science and Technology
(LIST) are acknowledged for organizing the permissions for the
experiments and providing discharge data for Weierbach 1 and
Colpach. We also want to thank Frauke K. Barthold and the two
anonymous reviewers, whose thorough remarks greatly helped to
improve the manuscript. This study is part of DFG-funded CAOS
project “From Catchments as Organised Systems to Models based
on Dynamic Functional Units” (FOR 1598).
The article processing charges for this open-access
publication were covered by a Research
Centre of the Helmholtz Association.


  • hillslope hydrology
  • preferential flow
  • subsurface flow
  • experimental hydrology
  • geophysical survey
  • ground penetrating radar


Dive into the research topics of 'Form and function in hillslope hydrology: Characterization of subsurface ow based on response observations'. Together they form a unique fingerprint.

Cite this