Patterns in river networks
River networks are among the most widespread and recognizable erosional landforms on Earth. In addition to transporting water and sediment across the continents, drainage networks develop characteristic scales and patterns that reflect the main factors that shape landscapes. Our aim is to understand the origin and evolution of these patterns. Taylor Perron, graduate student Paul Richardson, postdoc Ken Ferrier, and visiting student Mathieu Lapôtre recently showed that the familiar branching structure of tributaries at the uppermost reaches of river networks arises from two coupled instabilities in an eroding landscape, and that the size of the smallest river basins with tributaries (which varies from one landscape to the next) is a signature of the erodibility of the underlying rock and the ability of the land surface to produce runoff.
River networks also create striking patterns at finer spatial scales, as they interact with hillslopes. Valleys in many landscapes are evenly spaced, like the teeth on a comb. We showed that evenly spaced valley arise through a feedback in which neighboring valleys compete for water as they erode the landscape, and that the valley spacing is a signature of the relative strengths of river incision and soil creep.
Rivers are also commonly used to reconstruct tectonic patterns in space and time. In a collaboration with Leigh Royden (MIT), we explored the application of analytical solutions for the transient evolution of river elevation profiles to the reconstruction of a landscape's tectonic history. Our analysis shows that a river's elevation profile does not necessarily preserve a complete record of its uplift history, and provides a means of quantifying how much of that information may have been lost. In a separate paper, we show how a procedure for river profile analysis based on our analytical approach improves on conventional techniques.
Royden and Perron (2013), Solutions of the stream power equation and application to the evolution of river longitudinal profiles. J. Geophys. Res., in press, doi:10.1029/2012JF002493. PDF
Perron and Royden (2013). An integral approach to bedrock river profile analysis. Earth Surface Processes and Landforms, 38, 570-576, doi:10.1002/esp.3302. PDF
Perron et al. (2012), The root of branching river networks, Nature, 492, 100-103, doi:10.1038/nature11672. [link]
Perron and Fagherazzi (2012). The legacy of initial conditions in landscape evolution. Earth Surface Processes and Landforms, 37, 52-63, doi:10.1002/esp.2205. PDF
Perron et al. (2008). Controls on the spacing of first-order valleys. J. Geophys. Res., 113, F04016, doi:10.1029/2007JF000977. PDF
Perron et al. (2008). Spectral signatures of characteristic spatial scales and nonfractal structure in landscapes. J. Geophys. Res., 113, F04003, doi:10.1029/2007JF000866. PDF