Cenozoic river profile development in the Upper Lachlan catchment (SE Australia) as a test of quantitative fluvial incision models

Abstract

[1] We have used early Miocene valley-filling basalts to reconstruct fluvial long profiles in the Upper Lachlan catchment, SE Australia, in order to use these as well-constrained initial conditions in a forward model of fluvial incision. Many different fluvial incision algorithms have been proposed, and it is not clear at present which one of these best captures the behavior of bedrock rivers. We test five different formulations; the ability of these models to reproduce the observed present-day stream profiles and amounts of incision is assessed using a weighted-mean misfit criterion as well as the structure of the misfit function. The results show that for all models, parameter combinations can be found that reproduce the amounts of incision reasonably well. However, for some models, these best fit parameter combinations do not seem to have a physical significance, whereas for some others, best fit parameter combinations are such that the models tend to mimic the behavior of other models. Overall, best fit model predictions are obtained for a detachment-limited stream power model or an ''undercapacity'' model that includes a river width term that varies as a function of drainage area. The uncertainty in initial conditions does not have a strong impact on model outcomes. The model results suggest, however, that lithological variation may be responsible for variations in parameter values of a factor of 3-5.INDEX TERMS: 1824 Hydrology: Geomorphology (1625); 1815 Hydrology: Erosion and sedimentation; 3210 Mathematical Geophysics: Modeling; 9330 Information Related to Geographic Region: Australia; KEYWORDS: landscape evolution, bedrock rivers, fluvial incision models, river long-profile development, SE Australia Citation: van der Beek, P., and P. Bishop, Cenozoic river profile development in the Upper Lachlan catchment (SE Australia) as a test of quantitative fluvial incision models,

Influence of incision rate, rock strength, and bedload supply on bedrock river gradients and valley-flat widths: Field-based evidence and calibrations from western Alpine rivers (southeast France)

“…In particular, our data appear equally consistent with either "Undercapacity" (Beaumont et al, 1992) or "Tools" (Sklar and Dietrich, 1998) models, which take the effect of sediment flux on bedrock incision more fully into account. As shown by van der Beek and Bishop (2003), their end-member cases, if sediment flux is close to or far from carrying capacity, are equivalent to the transport-limited and detachment-limited stream power models, respectively. In most cases, both these models will also predict downstream transitions from "detachment-limited-like" to "transport-limitedlike" behavior, but they predict gentler transitions from one to the other, without a clearly defined critical drainage area (van der Beek and Bishop, 2003).…”

“…As shown by van der Beek and Bishop (2003), their end-member cases, if sediment flux is close to or far from carrying capacity, are equivalent to the transport-limited and detachment-limited stream power models, respectively. In most cases, both these models will also predict downstream transitions from "detachment-limited-like" to "transport-limitedlike" behavior, but they predict gentler transitions from one to the other, without a clearly defined critical drainage area (van der Beek and Bishop, 2003). Although these models are intuitively more realistic than the simple stream power approach, they are also more difficult to test because they require constraining variables such as sediment fluxes and channel widths.…”

Natural experiments in landscape evolution

“…If the longitudinal profile of a channel at some time in the past can be reconstructed, one can test the ability of a stream-incision model (like Equations 5 or 7) to reproduce the modern profile given the paleo-profile as a starting point. Several studies have used this approach on paleo-profiles that are delimited by volcanic deposits, strath terraces, and other markers (Rosenbloom and Anderson, 1994;Seidl et al, 1994;Stock and Montgomery, 1999;Whipple et al, 2000;van der Beek and Bishop, 2003;Crosby and Whipple, 2006;Harkins et al, 2007;Oskin and Burbank, 2007;Reinhardt et al, 2007). One potential limitation of this approach is that it ignores possible changes through time in sediment flux to the channel as the surrounding topography evolves.…”

“…Whipple et al, 2000), radiometric dating of volcanic deposits (e.g. Stock and Montgomery, 1999;van der Beek and Bishop, 2003), and dating of strath terraces by radiocarbon, luminescence or cosmogenic methods (e.g. Pazzaglia et al, 1998;Hancock et al, 1998) are just a few examples.…”

Flood magnitude–frequency and lithologic control on bedrock river incision in post-orogenic terrain

“…(1)) of a bedrock channel declines with ongoing topographic decay, then Sandy Creek gorge ought to exemplify a very 'inefficient' system (cf. Stock and Montgomery, 1999;van der Beek and Bishop, 2003). Accordingly, low erosional efficiency might manifest in some combination of (1) coarse bed texture (i.e.…”