My research involves environmental fluid mechanics and transport theory applied to problems in geomorphology and hydrology, and the intersection of these fields with ecology. This work combines theoretical, experimental, computational and field-based components aimed at understanding the dynamics of Earth surface systems spanning human to geomorphic time scales. I have taught courses in geology, hydrology and geomorphology, transport processes in Earth and environmental systems, fluid dynamics, and probability and statistics.
Our current research is centered on theoretical, experimental and field-based studies of the probabilistic physics of sediment particle motions. It is aimed at clarifying our understanding of the transport and dispersal of sediment and sediment-borne substances in rivers and on hillslopes. In addition to its interesting technical aspects, this work has an important philosophical basis.
Namely, in learning how to describe the behavior of mechanical systems, mostly we are initially exposed to deterministic examples. We study Newton’s laws as these pertain to simple particle systems, and then move on to the behavior of solids and fluids treated as continuous materials. The formalism is unambiguous, and describing the behavior of a well constrained system is in principle straightforward. Indeed, much (although not all) of the legacy of geophysics resides in the determinism of continuum mechanics. Perhaps it is therefore natural that we might envision that a mechanistic description of the behavior of a system implies that such a description ought to be, or perhaps only can be, a deterministic one. Such a perception represents a lost opportunity. The most elegant counterpoint example is the field of classical statistical mechanics — devoted specifically to the probabilistic (i.e., non-deterministic) treatment of the behavior of gas particle systems in order to justify the principles of thermodynamics — yet which is no less mechanical in its conceptualization of this behavior than, say, the application of Newton’s laws to the behavior of a deterministic system consisting of the interactions of a few billiard balls or the players of the solar system, or involving the motion of a Newtonian fluid subject to specific initial and boundary conditions.
Once steeped in the language of mechanics, we understandably take comfort in mechanistic descriptions of system behavior. Specifically, we invest trust in the underlying foundation, and implied rigor, provided by classical mechanics. This is a good thing. But given the complexity and the uncertainty in describing the behavior of sediment systems, here it is essential to consider the idea that the concepts and language of probability are well suited to the problem of describing this behavior — precisely because of the complexity and uncertainty involved — relaxing our expectations that a deterministic-like relationship exists between, say, the flux of bed-load sediment and the fluid stress imposed on the streambed, or the flux of sediment on a hillslope and the local land-surface slope. This idea of leaning on probability to describe the behavior of sediment systems is not as straightforward as describing the behavior of idealized gas particle systems. Nonetheless, the objective is the same: to be mechanistic, yet probabilistic. These world views are entirely compatible.
Within this context, we currently are pursuing work on probabilistic descriptions of bed-load sediment transport within turbulent shear flows. This is mostly centered on detailed experimental measurements of particle motions using high-speed imaging, and PIV measurements of near-bed fluid motions. Our efforts are aimed at probabilistic formulations of transport, including descriptions of particle diffusion (or ‘dispersion’), appealing to methods and techniques of classical statistical mechanics. We also are focusing on the problem of describing effects of patchy, intermittent particle motions that are mostly rarefied — conditions that are at odds with continuum based formulations of transport.
In addition, we are pursuing work on probabilistic formulations of sediment transport on hillslopes. This involves both experiments and field-based measurements to inform theory and computational models of hillslope evolution. In addition to analysis of archived DEM data and descriptions of sediment behavior on a laboratory scale “hillslope,” we are pursuing field-based studies of long hillslopes in the southern Appalachian Mountains, and age-dated glacial moraines on the east side of the Sierra Nevada Mountains. Our efforts are aimed at clarifying the significance of local versus nonlocal sediment transport in steepland topography, including how these styles of transport influence the behavior of two-dimensional topography.
Dylan Casler (B.A.) Physics, Mathematics
Tyler Doane (Ph.D.) Earth and Environmental Sciences
Siobhan Fathel (Ph.D.) Environmental Science
Selected Publications (*Denotes Student Author)
Furbish, D. J., S. L. Fathel*, M. W. Schmeeckle, D. J. Jerolmack, and R. Schumer (2016), The elements and richness of particle diffusion during sediment transport at small timescales. (in preparation)
Grieve, S. W. D., S. M. Mudd, D. T. Milodowski, F. J. Clubb, and D. J. Furbish (2016), How does grid-resolution modulate the topographic expression of geomorphic processes? (in review)
*Fathel, S. L., D. J. Furbish, and M. W. Schmeeckle (2016), Parsing anomalous versus normal diffusive behavior of bed load sediment particles, Earth Surface Processes and Landforms, doi: 10.1002/esp.3994.
Furbish, D. J., M. W. Schmeeckle, R. Schumer, and S. L. Fathel* (2016), Probability distributions of bed-load particle velocities, accelerations, hop distances and travel times informed by Jaynes’s principle of maximum entropy, Journal of Geophysical Research – Earth Surface, doi: 10.1002/2016JF003833.
Furbish, D. J., S. L. Fathel*, and M. W. Schmeeckle (2016), Particle motions and bed load theory: The entrainment forms of the flux and the Exner equation, in Tsutsumi, D. and Laronne, J. B. (eds.), Gravel-bed Rivers: Processes and Disasters, John Wiley and Sons. (in press)
*Fathel, S. L., D. J. Furbish, and M. W. Schmeeckle (2015), Experimental evidence of statistical ensemble behavior in bed load sediment transport, Journal of Geophysical Research – Earth Surface, 120, doi: 10.1002/2015JF003552.
Furbish, D. J., and J. J. Roering (2013), Sediment disentrainment and the concept of local versus nonlocal transport on hillslopes, Journal of Geophysical Research – Earth Surface, 118, 1-16, doi: 10.1002/jgrf.20071.
Furbish, D. J., and M. W. Schmeeckle (2013), A probabilistic derivation of the exponential-like distribution of bed load particle velocities, Water Resources Research, 49, 1537-1551, doi: 10.1002/wrcr.20074.
Furbish, D. J., P. K. Haff, J. C. Roseberry*, and M. W. Schmeeckle (2012), A probabilistic description of the bed load sediment flux: 1. Theory, Journal of Geophysical Research – Earth Surface, 117, F03031, doi: 10.1029/2012JF002352.
*Roseberry, J. C., M. W. Schmeeckle, and D. J. Furbish (2012), A probabilistic description of the bed load sediment flux: 2. Particle activity and motions, Journal of Geophysical Research – Earth Surface, 117, F03032, doi: 10.1029/2012JF002353.
Furbish, D. J., J. C. Roseberry*, and M. W. Schmeeckle (2012), A probabilistic description of the bed load sediment flux: 3. The particle velocity distribution and the diffusive flux, Journal of Geophysical Research – Earth Surface, 117, F03033, doi: 10.1029/2012JF002355.
Furbish, D. J., A. E. Ball*, and M. W. Schmeeckle (2012), A probabilistic description of the bed load sediment flux: 4: Fickian diffusion at low transport rates, Journal of Geophysical Research – Earth Surface, 117, F03034, doi: 10.1029/2012JF002356.
Furbish, D. J. and Haff, P. K. (2010) From divots to swales: Hillslope sediment transport across divers length scales, Journal of Geophysical Research – Earth Surface, 115, F03001, doi: 10.1029/2009JF001576.
*Covey, A. K., D. J. Furbish, and K. S. Savage (2010) Earthworms as agents for arsenic transport and transformation in roxarsone-impacted soil microcosms: A µ-XANES and modeling study, Geoderma, 156, 99-111, doi: 10.1016/j.geoderma.2010.02.004.
*Challener, R. C., M. F. Miller, D. J. Furbish, and J. McClintock (2009) An evaluation of sand grain crushing in the sand dollar Mellita tenuis (Echinoidea: Echinodermata), Aquatic Biology, 7, 261-268, doi: 10.33354/ab00199
Furbish, D. J., P. K. Haff, W. E. Dietrich, and A. M. Heimsath (2009) Statistical description of slope-dependent soil transport and the diffusion-like coefficient, Journal of Geophysical Research – Earth Surface, 114,
Furbish, D. J., E. M. Childs*, P. K. Haff, and M. W. Schmeeckle (2009) Rain splash of soil grains as a stochastic advection-dispersion process, with implications for desert plant-soil interactions and land-surface evolution. Journal of Geophysical Research – Earth Surface, 114, doi: 10.1029/2009JF001265.
Furbish, D. J., M. W. Schmeeckle, and J. J. Roering (2008) Thermal and force-chain effects in an experimental, sloping granular shear flow. Earth Surface Processes and Landforms, 33, 2108-2117, doi: 10.1002/esp.1655.
*Mudd, S. M. and D. J. Furbish (2007) Responses of soil-mantled hillslopes to transient channel incision rates. Journal of Geophysical Research – Earth Surface, 112, F03S18, doi: 10.1029/2006JF000516.
Furbish, D. J., K. K. Hamner*, M. W. Schmeeckle, M. N. Borosund*, and S. M. Mudd* (2007) Rain splash of dry sand revealed by high-speed imaging and sticky-paper splash targets. Journal of Geophysical Research – Earth Surface, 112, F01001, doi: 10.1029/2006JF000498.
Furbish, D. J. and S. Fagherazzi (2001), Stability of creeping soil and implications for hillslope evolution, Water Resources Research, 37, 2607-2618.
Furbish, D. J. (1998) Irregular bed forms in steep, rough channels: 1. Stability analysis. Water Resources Research, 34, 3635-3648, doi: 10.1029/98WR02339.
Furbish, D. J., S. D. Thorne*, T. C. Byrd*, J. Warburton, J. J. Cudney*, and R. W. Handel* (1998) Irregular bed forms in steep, rough channels: 2. Field observations.Water Resources Research, 34, 3649-3659,
Furbish, D. J. (1997), Fluid Physics in Geology, Oxford University Press.