Synthetic River Valleys
Gregory B. Pasternack and Rocko A. Brown
There are two phases of knowledge production: analysis and synthesis. During the analysis phase, scientists aim to explore nature and discern natural laws. Near-census river science is a state-of-the-art approach to analyzing natural rivers at this time. However, the history of science shows that scientists can end up satisfied with principles that are surprising crude with low explanatory power. Without being forced to put scientific knowledge to the test in real-world applications, there is not sufficient necessity and pressure to insure that scientific ideas are accurate and complete. That is why there needs to be a synthesis phase. During synthesis, scientists collaborate with engineers and technologists to bring their ideas to practical application. Applications may take place in a lab setting, in a computer program, or through real-world construction projects.
In the Pasternack Lab we straddle analysis and synthesis to keep pushing ourselves onward using necessity as a driver for creative exploration. Synthetic river valleys (SRVs) is the most advanced scheme yet that we have developed to push synthesis of scientific ideas into practical solutions. The concepts and methods underlying SRVs was spearheaded by Ph.D. candidate Rocko Brown. It has to do with designing entire river corridors with many degrees of freedom, taking advantage of some prescriptive scientific laws, but not bounded by them either. Nature is an open system with surprising flexibility and dynamism. Synthetic river valleys open the possibility of exploring a wide array of landscape possibilities for both scientific purposes as well as societal ones. In a few case, SRVs have already been used to design river rehabilitation projects in collaboration with the private sector. However, this is an active area of research that is still young and has a lot more possibilities to explore.
Below are two relatively simple "bare Earth" SRVs to illustrate what they can look like. These river valleys contain a bed slope, bed elevation undulation, channel width undulation, channel-cross section asymmetry, floodplain side slope, and undulating valley walls. Several of the size, shape, and undulation variables are linked through geometric correlation structures, which are some of the underlying ways that landforms create organized, orderly spatial patterns. There are many additional features that can be added to a river corridor to layer complexity and diversity on top of these basic structures. What these exmaples reveal is that a relatively small number of linnked variables can generate quite distinct river corridors.
We are continuing to make progress with our SRV algorithm and scope of studies.In one line of research we are investigating and code more variability functions to expand the geometric modeling capabilities of the method. In another line of research we are building SRV archetypes for many different kinds of rivers in support of regional flow and habitat management. Finally, we are exploring ways to automate SRV design by drawing on landscape attributes at larger scales that help set the local features. For example, the regional SRV below shows 3 different SRVs nested into a larger landscape terrain block. Everything in the image is entirely synthetic, yet generated analytically. This illustrates the potential of where this technology can go.
- Brown, R.A., Pasternack, G.B., Wallender, W.W. 2014. Synthetic River Valleys: Creating Prescribed Topography for Form-Process Inquiry and River Rehabilitation Design. Geomorphology 214: 40-55. http://dx.doi.org/10.1016/j.geomorph.2014.02.025.
- Brown, R. A., Pasternack, G. B., Lin, T. 2015. The topographic design of river channels for form-process linkages for river restoration. Environmental Management, 57 (4): 929-942. doi: 10.1007/s00267-015-0648-0
- Pasternack, G. B., Brown, R. A. 2016. Designing rivers with multiple scales of channel and floodplain variation to yield diverse processes and ecosystem services. 11th International Conference on Ecohydraulics, February 7-12, Melbourne, Australia.