Modelling soil erosion with a downscaled landscape evolution model

Abstract

The measurement and prediction of soil erosion is important for understanding both natural and disturbed landscape systems. In particular numerical models of soil erosion are important tools for managing landscapes as well as understanding how they have evolved over time. Over the last 40 years a variety of methods have been used to determine rates of soil loss from a landscape and these can be loosely categorized into empirical and physically based models. Alternatively, physically based landscape evolution models (LEMs) have been developed that provide information on soil erosion rates at much longer decadal or centennial scales, over large spatial scales and examine how they may respond to environmental and climatic changes. Both soil erosion LEMs are interested in similar outcomes (landscape development and sediment delivery) yet have quite different methodologies and parameterizations. This paper applies a LEM (the CAESAR model) for the first time at time and space scales where soil erosion models have largely been used. It tests the ability of the LEM to predict soil erosion on a 30 m experimental plot on a trial rehabilitated landform in the Northern Territory, Australia. It then continues to discuss the synergies and differences between soil erosion and LEMs.The results demonstrate that once calibrated for the site hydrology, predicted suspended sediment and bedload yields from CAESAR show a close correspondence in both volume and timing of field measured data. The model also predicts, at decadal scales, sediment loads close to that of field measured data. Findings indicate that the small-scale drainage network that forms within these erosion plots is an important control on the timing and magnitude of sediment delivery. Therefore, it is important to use models that can alter the DEM to reflect changing topography and drainage network as well as having a greater emphasis on channel processes.

The sensitivity of landscape evolution models to spatial and temporal rainfall resolution

“…CAESAR-Lisflood can already use precipitation data over a range of temporal resolutions, and for most previous applications this resolution has been hourly, though the model has also been run with daily (Coulthard et al, 2013b) and at 10 min resolutions (Coulthard et al, 2012a). To enable spatially variable precipitation inputs and hydrology, CAESARLisflood was modified so that precipitation rates could be input via spatially fixed predefined areas.…”

Climate, tectonics or morphology: what signals can we see in drainage basin sediment yields?

“…As stated in the model description, CAESAR has successfully simulated landscape evolution in a range of environments Macklin, 2001, 2003;Coulthard et al, 2012a;Hancock et al, 2011;Welsh et al, 2009), but it is important to question whether the non-linear response of the model is simply a model by-product or a representation of actual basin dynamics? CAESAR has a long history of modelling the non-linear reaction of catchments from 1998 through to 2010 Coulthard et al, 1998Coulthard et al, , 2005Van De Wiel and Coulthard, 2010) and given that similar non-linear dynamics have been well documented in fluvial systems (Cudden and Hoey, 2003;Gomez and Phillips, 1999;Hooke, 2003;Stølum, 1998), we consider the simulation of non-linear sediment dynamics in CAESAR genuine.…”

“…CAESAR was initially developed to examine the relative roles of climate and land cover change on geomorphology and sediment yield and has been applied to a range of real drainage basins with outputs successfully compared to independent field data. These examples include patterns of sedimentation in Alpine environment (Welsh et al, 2009) sediment yields and longer term lowering rates from Northern Australia (Hancock et al, 2010), comparisons to field plot experiments (Coulthard et al, 2012a), predicting patterns of contaminated sediment dispersal (Coulthard and Macklin, 2003) and simulating 9000 yr of drainage basin evolution in the UK (Coulthard and Macklin, 2001).…”

Exploring the sensitivity on a soil area-slope-grading relationship to changes in process parameters using a pedogenesis model

“…Two particle size distribution data sets were collected from the Ranger Uranium Mine (Northern Territory, Australia) spoil site (Willgoose and Riley, 1998;Sharmeen and Willgoose, 2007;Cohen et al, 2009;Coulthard et al, 2012). The third and fourth gradings were created from the previous two gradings to simulate the subsurface bedrock conditions.…”

“…-Ranger2a: the second grading distribution was used by Coulthard et al (2012) in their soil erosion modelling experiments and has a maximum diameter of 200 mm. The Coulthard data set includes a coarse fraction which is not included in Ranger1a, has a median diameter of 40 mm, and has a maximum diameter of 200 mm.…”