Modelling landscape evolution

Abstract

Geomorphology is currently in a period of resurgence as we seek to explain the diversity, origins and dynamics of terrain on the Earth and other planets in an era of increased environmental awareness. Yet there is a great deal we still do not know about the physics and chemistry of the processes that weaken rock and transport mass across a planet's surface. Discovering and refi ning the relevant geomorphic transport functions requires a combination of careful fi eld measurements, lab experiments, and use of longer-term natural experiments to test current theory and develop new understandings. Landscape evolution models have an important role to play in sharpening our thinking, guiding us toward the right observables, and mapping out the logical consequences of transport laws, both alone and in combination with other salient processes. Improved quantitative characterization of terrain and process, and an ever-improving theory that describes the continual modifi cation of topography by the many and varied processes that shape it, together with improved observation and qualitative and quantitative modelling of geology, vegetation and erosion processes, will provide insights into the mechanisms that control catchment form and function. This paper reviews landscape theory -in the form of numerical models of drainage basin evolution and the current knowledge gaps and future computing challenges that exist.

What makes Darwinian hydrology "Darwinian"? Asking a different kind of question about landscapes

“…Other combinations are more stable, in the sense that they persist for a longer period of time. This assumption is supported by ideas regarding the persistence of and convergence towards geomorphic "forms" (Brunsden and Thornes, 1979) and the resilience and stability of ecosystems (Tucker and Hancock, 2010), both of which posit that there are system configurations that persist while others are transient. The stable configurations of landscapes need not be static or even steady state under this assumption -they need only to have combinations of process dominance and water-balance partitioning that change more slowly over time than other combinations.…”

“…Such models could help evaluate the "reachability" requirement of the Darwinian hypothesis and quantify the relative duration of different configurations of landscapes. There are great challenges to be overcome in finding the appropriate ways to represent the feedbacks between hydrology and other longer-term landscape processes and in the parameterization of these relationships from observations, but progress is being made (Hopp et al, 2009;Tucker and Hancock, 2010). For example, Pelletier et al (2013) recently circumvented these feedbacks by connecting effective process parameters to a higher-order variable (effective energy and mass transfer -EEMT) that captures water and energy constraints on landscape-forming processes and used this to explain variations in topography, soil thickness, land forms, and biomass across a climate gradient in southern Arizona.…”

Landscape reorganization under changing climatic forcing: Results from an experimental landscape

“…The generally expressed view is that these topographic changes are driven by river channel incision or aggradation which in turn drives a hillslope response, i.e., rivers respond and hillslopes follow [Whipple and Tucker, 1999;Dietrich et al, 2003;Whittaker, 2012]. Thus, most numerical studies have focused on the changing rates of channel erosion (typically by increasing the erosivity coefficient K in the stream-power relation E5KA m S n , where E, A, and S denote the erosion rate, upstream drainage area, and channel slope, respectively; K, m, and n are the constants) [Tucker and Slingerland, 1997;Tucker and Hancock, 2010;Lague, 2014].…”

“…For example, Hartshorn et al [2002] argued that valley lowering is driven by frequent, moderate intensity floods which mobilize the coarse bed load and abrade underlying bedrock while D'Arcy and Whittaker [2014] found that channel steepness is significantly suppressed by higher precipitation due to a concomitant increase in stream power. Hillslopes are then expected to passively follow decreased or increased rates of base-level lowering by either (a) steepening or lowering hillslope angle: in transport-limited (soil mantled) conditions, the rate of soil creep/mass movement will slowly change due to a change in base level and increased/decreased soil diffusivity [Fernandes and Dietrich, 1997]; or (b) in high-relief terrain maintain roughly linear (threshold) hillslopes but increase/decrease the rate of landsliding [Burbank et al, 1996;Tucker and Bras, 1998;Tucker and Hancock, 2010]. Crucially, Gabet et al [2004] while agreeing with the view that mean topographic elevation lowers in response to increased precipitation also found that relief is inversely related to precipitation.…”

Soilscape evolution of aeolian-dominated hillslopes during the Holocene: investigation of sediment transport mechanisms and climatic–anthropogenic drivers

“…practice in many landscape-evolution models (Tucker and Hancock, 2010), the interaction between them is often uncertain (Hancock et al, 2002), particularly under unique circumstances like in this field site: fine-grained aeolian-dominated soils with a high degree of temporal variation in soil supply. Cohen et al (2015) used the mARM5D model to investigate the differences between bedrock-and aeoliandominated soilscape evolution.…”