Simulation modeling and statistical classification of escarpment planforms

Abstract

Nearly horizontal sedimentary sequences are typically eroded into escarpments capped by resistant rock layers. These escarpments record in planform the spatial variation in erosional processes. Simulation models have been constructed of scarp development by three processes, scarp backwasting, fluvial erosion, and groundwater sapping, acting singly or in combination. Scarp backwasting produces planforms characterized by broad, shallow reentrants and sharply pointed headlands. Fluvial erosion creates dendritic, sharply terminated canyons which gradually widen downstream because of superimposed backwasting. Groundwater sapping produces weakly branched canyons of nearly constant width with generally rounded headwalls. A number of morphometric variables are measured on natural and simulated scarps as well as lava flows, glacially eroded mountain fronts, and eroded tabular igneous intrusions. A discriminant analysis is able to classify 478 of these planforms into 9 categories with 87% accuracy.

Modeling the effects of vegetation‐erosion coupling on landscape evolution

“…As distinct from the 2-dimensional (Culling, 1960;Scheidegger, 1961;Snow and Slingerland, 1987;Paola et al, 1992;Robinson and Slingerland, 1998;Roe et al, 2001), or purely hillslope- (Ahnert, 1976;Favis-Mortlock et al, 2000) or channel-based (Webb, 1995) 3-dimensional models, landscape evolution models represent the topography by a mesh of points spanning both hillslope and channel elements (Willgoose et al, 1991;Howard, 1994;Howard et al, 1994;Tucker and Slingerland, 1997;Tucker and Bras, 2000). In addition to fluvial and diffusional processes commonly modeled (Howard, 1994), the register of geomorphic processes also includes tectonics (Koons, 1989;Beaumont et al, 1992;Tucker and Slingerland, 1994;Kooi and Beaumont, 1994), weathering (Braun et al, 2001), mass wasting (Howard, 1997) and seepage erosion (Howard, 1995;Lou, 2001). Models have also been used to address climate and landuse changes (Coulthard et al, 2000;Evans and Willgoose, 2000) and vegetation dynamics (Howard, 1999;Lancaster et al, 2001).…”

Implications of bank failures and fluvial erosion for gully development: Field observations and modeling

“…In modeling gully erosion numerically, identifying the model cells that host a scarp face is important for at least two reasons. First, in a U-shaped gully the scarp face is subject to lateral retreat in the direction normal to the scarp face in the horizontal plane [Howard, 1995]. Second, conventional methods for local slope calculation based on finite differences of elevation rely on the assumption that the surface z(x, y, t) is continuous.…”

“…The inherent complexity in gully development in low-gradient environments makes it difficult to develop simple topography-based models [Montgomery, 1999]. Some notable contributions, however, in numerical modeling of gully evolution include modeling planform evolution of drainage networks by groundwater seepage [Howard and McLane, 1988;Howard, 1995], and mass wasting of over steepened scarps [Howard, 1999;Kirkby and Bull, 2000;Kirkby et al, 2003]. In these studies gullying processes are modeled implicitly using simple rules.…”

Spontaneous channelization in permeable ground: theory, experiment, and observation

“…Howard & McLane (1988) studied the rate of seepage erosion in a narrow two-dimensional flow tank. Howard (1994Howard ( , 1995 has carried out computer simulation modeling of valley development by groundwater sapping.…”