Channels shape our surroundings, the geologic record, and alien environments from Mars to the ocean floor. My research asks: how can we use fluvial features to reconstruct the past and forecast the future?

Bedrock river valley form and evolution

Clockwise from upper left: the San Juan River, Utah; Mattole River, California; Colorado River, Texas; Beaver River, Alberta, Canada.

Bedrock river valleys are fundamental to planetary landscapes. Valley morphologies—from slot canyons with incised meanders to wide valleys with strath terraces—may record environmental history, including changes in climate, tectonics, and sea-level. Yet processes of erosion and deposition intrinsic to river systems also shape valleys, independent of changes in external forcing. I use forward modeling to test hypotheses for valley development over millennial timescales, and compare model predictions to natural river valleys. By quantifying how channels develop valleys under steady forcing, this work has yielded a new framework for distinguishing valley forms with significance for interpreting regional geologic history.

Related papers:

  • Limaye, A. B. S., and Lamb, M. P., 2016, Numerical model predictions of autogenic fluvial terraces and comparison to climate change expectations, Journal of Geophysical Research – Earth Surface 121, doi:10.1002/2014JF003392. [PDF] [Movie] [Eos]
  • Limaye, A. B. S., and Lamb, M. P., 2014, Numerical simulations of bedrock valley evolution by meandering rivers with variable bank material, Journal of Geophysical Research – Earth Surface, doi:10.1002/2013JF002997. [PDF] [Eos]

Submarine channel dynamics and deposits

An experimental submarine landscape at St. Anthony Falls Laboratory.

Channels abound not only on planetary surfaces, but also on Earth’s seafloor. These submarine channels host sediment-laden density currents, which transport clastic sediment from continental margins to the deep ocean. Viewed in geophysical images, submarine channels often look like river channels—but the strength of the analogy remains incompletely understood. To compare and contrast the morphodynamics and sedimentary deposits of rivers and submarine channels, I worked with colleagues at SAFL to design and run experiments in a new flume that can mimic both environments. The experiments suggest that compared to rivers, submarine channels develop both larger flow depths and slopes to transport a given sediment load. Read more about the setup at the Sediment Experimentalists Network Knowledge Base.

Related papers:

  • Limaye, A. B., Grimaud, J.-L., Lai, S. Y. J., Foreman, Y., Komatsu, Y., and Paola, C., accepted, Geometry and dynamics of braided channels, bars, and associated deposits under experimental density currents, Sedimentology.
  • Lai, S. Y. J. , Hung, S. S. C., Foreman, B. Z., Limaye, A. B., Grimaud, J. L., and Paola, C., 2017, Stream power controls the braiding intensity of submarine channels similarly to rivers, Geophysical Research Letters 44, doi:10.1002/2017GL072964[PDF]

Channel networks

A visualization of channel network geometry for the Platte River, Nebraska.

Quantitative measures of channel network geometry inform diverse applications in hydrology, sediment transport, ecology, hazard assessment, and stratigraphic prediction. These uses require a clear, objectively defined channel network. Automated techniques for extracting channels from topography are well developed for convergent channel networks and identify flow paths based on land-surface gradients. These techniques—even when they allow multiple flow paths—do not consistently capture channel networks with frequent bifurcations (e.g., in rivers, deltas, and alluvial fans).  In practice, channels are commonly mapped using observed inundation extent, and I generalized this approach using a simplified flow model. A case study for the Platte River, Nebraska, revealed that several key descriptors of channel network geometry reach extremal values at a corresponding reference discharge that can be used to compare the geometry of multithread rivers. This approach extends channel network extraction from topography to the full spectrum of channel patterns, with the potential for comparing diverse channel patterns at scales from laboratory experiments to natural landscapes.

Related papers:

Limaye, A. B., 2017, Extraction of multithread channel networks with a reduced-complexity flow model, Journal of Geophysical Research: Earth Surface 122, doi:10.1002/2016JF004175[PDF] [Data repository]

The sedimentary record of Mars climate

mars-ocean-river-deltaA comparison of low-latitude sedimentary deposits on Mars with the Selenga Delta, Russia.

The landscapes and sedimentary deposits of Mars hold a key record planetary climate. Ancient fluvial deposits at low latitudes record periods of surface water flow, while ice-rich deposits at mid- and high latitudes record more recent climate evolution through high-amplitude changes Mars’ orbit.  I use high-resolution satellite images and digital elevation models to identify and quantify stratigraphic relationships in these diverse settings in order to interpret Martian climate history. This work has yielded the identification of a repeating, meter-scale sequence in distantly separated outcrops of the north polar layered deposits, which suggests a quasi-periodic deposition process; and sedimentary evidence that a standing body of water once occupied the northern lowlands of Mars.

Related papers:

  • DiBiase, R. A., Limaye, A. B., Scheingross, J. S., Fischer, W. W. and Lamb, M. P., 2013, Deltaic deposits at Aeolis Dorsa: Sedimentary evidence for a large body of water in the northern plains of Mars, Journal of Geophysical ResearchPlanets 118, p. 1-18, doi: 10.1002/jgre.20100. [PDF] []
  • Limaye, A. B. S., Aharonson, O., and Perron, J. T., 2012, Detailed stratigraphy and bed thickness of the Mars north and south polar layered deposits, Journal of Geophysical ResearchPlanets 117, doi:10.1029/2011JE003961. [PDF]
  • Hubbard, B., Milliken, R. E., Kargel, J. S., Limaye, A., and Souness, C., 2011, Geomorphological characterisation and interpretation of a mid-latitude glacier-like form: Hellas Planitia, Mars, Icarus 21, 330-346. [PDF]

Numerical methods for tracking river evolution

A simulation of a vertically incising, meandering river.

Sinuous channels abound on planetary surfaces, for example in the form of meandering rivers and delta channels. Such channels often migrate laterally and interact with banks of different strengths due to differences in lithology and sediment grain size. This interplay between the channel and its surroundings shapes many environments, but efforts to explore this interaction with numerical models have been hampered by the evolving, curvilinear geometry of channel boundaries. I developed a novel, vector-based method for land surface- and subsurface-material tracking that overcomes the numerical artifacts inherent in commonly used, grid-based techniques. The vector-based framework provides new opportunities for exploring the long-term co-evolution of sinuous channels and surrounding landscapes.

Related papers:

  • Limaye, A. B. S., and Lamb, M. P., 2013, A vector-based approach to bank-material tracking in coupled models of meandering and landscape evolution, Journal of Geophysical Research – Earth Surface 118, doi: 10.1002/2013JF002854. [PDF]