ORCID Profile
0000-0002-1619-1265
Current Organisation
University of Newcastle Australia
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Publisher: Copernicus GmbH
Date: 08-2016
Abstract: Abstract. This paper generalises the physical dependence of the relationship between contributing area, local slope, and the surface soil grading using a pedogenesis model and allows an exploration of soilscape self-organisation. A parametric study was carried out using different parent materials, erosion, and weathering mechanisms. These simulations confirmed the generality of the area-slope-d50 relationship. The relationship is also true for other statistics of soil grading (e.g. d10,d90) and robust for different depths within the profile. For small area-slope regimes (i.e. hillslopes with small areas and/or slopes) only the smallest particles can be mobilised by erosion and the area-slope-d50 relationship appears to reflect the erosion model and its Shield's Stress threshold. For higher area-slope regimes, total mobilization of the entire soil grading occurs and self-organisation reflects the relative entrainment of different size fractions. Occasionally the interaction between the in-profile weathering and surface erosion draws the bedrock to the surface and forms a bedrock outcrop. The study also shows the influence on different depth-dependent in-profile weathering functions in the formation of the equilibrium soil profile and the grading characteristics of the soil within the profile. We outline the potential of this new model and its ability to numerically explore soil and landscape properties.
Publisher: Copernicus GmbH
Date: 20-01-2016
Abstract: Abstract. This paper generalises the physical dependence of the relationship between contributing area, local slope, and the surface soil grading first described by Cohen et al, [2009, 2010] using their mARM1D and mARM3D pedogenesis models. A more general computational model, SSSPAM5D, extending the conceptualisation of mARM3D has been developed to further our exploration of soilscape self-organisation. A parametric study was carried out using different parent materials, erosion, and weathering mechanisms. These simulations confirmed the generality of the area-slope-d50 relationship. The relationship is also true for other statistics of soil grading (e.g. d10, d90) and robust for different depths within the profile. For small area-slope regimes (i.e. hillslopes with small areas and/or slopes) only the smallest particles can be mobilised by erosion and the area-slope-d50 relationship appears to reflect the erosion model and its Shields Stress threshold. For higher area-slope regimes, total mobilization of the entire soil grading occurs and self-organisation reflects the relative entrainment of different size fractions. Occasionally the interaction between the in-profile weathering and surface erosion draws the bedrock to the surface and forms a bedrock outcrop. The study also shows the influence on different depth dependent in-profile weathering functions in the formation of the equilibrium soil profile and the grading characteristics of the soil within the profile.
Publisher: Copernicus GmbH
Date: 26-06-2019
Abstract: Abstract. This paper describes the coupling of the State Space Soil Production and Assessment Model (SSSPAM) soilscape evolution model with a landform evolution model to integrate soil profile dynamics and landform evolution. SSSPAM is a computationally efficient soil evolution model which was formulated by generalising the mARM3D modelling framework to further explore the soil profile self-organisation in space and time, as well as its dynamic evolution. The landform evolution was integrated into SSSPAM by incorporating the processes of deposition and elevation changes resulting from erosion and deposition. The complexities of the physically based process equations were simplified by introducing a state-space matrix methodology that allows efficient simulation of mechanistically linked landscape and pedogenesis processes for catena spatial scales. SSSPAM explicitly describes the particle size grading of the entire soil profile at different soil depths, tracks the sediment grading of the flow, and calculates the elevation difference caused by erosion and deposition at every point in the soilscape at each time step. The landform evolution model allows the landform to change in response to (1) erosion and deposition and (2) spatial organisation of the co-evolving soils. This allows comprehensive analysis of soil landform interactions and soil self-organisation. SSSPAM simulates fluvial erosion, armouring, physical weathering, and sediment deposition. The modular nature of the SSSPAM framework allows the integration of other pedogenesis processes to be easily incorporated. This paper presents the initial results of soil profile evolution on a dynamic landform. These simulations were carried out on a simple linear hillslope to understand the relationships between soil characteristics and the geomorphic attributes (e.g. slope, area). Process interactions which lead to such relationships were also identified. The influence of the depth-dependent weathering function on soilscape and landform evolution was also explored. These simulations show that the balance between erosion rate and sediment load in the flow accounts for the variability in spatial soil characteristics while the depth-dependent weathering function has a major influence on soil formation and landform evolution. The results demonstrate the ability of SSSPAM to explore hillslope- and catchment-scale soil and landscape evolution in a coupled framework.
Publisher: Copernicus GmbH
Date: 22-04-2020
DOI: 10.5194/HESS-24-1985-2020
Abstract: Abstract. Global agricultural drought policy has shifted towards promoting drought preparedness and climate resilience in favor of disaster-relief-based strategies. For this approach to be successful, drought predictability and methods for assessing the many aspects of drought need to be improved. Therefore, this study aims to bring together meteorological and hydrological measures of drought as well as vegetation and soil moisture data to assess how droughts begin, propagate and subsequently terminate for a catchment in eastern Australia. For the study area, 13 meteorological drought periods persisting more than 6 months were identified over the last 100 years. During these periods, vegetation health, soil moisture and streamflow declined however, all of the indicators recovered quickly post-drought, with no evidence of extended impacts on the rainfall–runoff response, as has been observed elsewhere. Furthermore, drought initiation and propagation were found to be tightly coupled to the combined state of large-scale ocean–atmosphere climate drivers (e.g., the El Niño–Southern Oscillation, the Indian Ocean Dipole and the Southern Annular Mode), whereas termination was caused by persistent synoptic systems (e.g., low-pressure troughs). The combination of climatic factors, topography, soils and vegetation are believed to be what makes the study catchments more resilient to drought than others in eastern Australia. This study ersifies traditional approaches to studying droughts by quantifying the catchment response to drought using a range of measures that could also be applied in other catchments globally. This is a key step towards improved drought management.
Publisher: Copernicus GmbH
Date: 06-12-2018
Abstract: Abstract. The evaluation and verification of landscape evolution models (LEMs) has long been limited by a lack of suitable observational data and statistical measures which can fully capture the complexity of landscape changes. This lack of data limits the use of objective function based evaluation prolific in other modelling fields, and restricts the application of sensitivity analyses in the models and the consequent assessment of model uncertainties. To overcome this deficiency, a novel model function approach has been developed, with each model function representing an aspect of model behaviour, which allows for the application of sensitivity analyses. The model function approach is used to assess the relative sensitivity of the CAESAR-Lisflood LEM to a set of model parameters by applying the Morris method sensitivity analysis for two contrasting catchments. The test revealed that the model was most sensitive to the choice of the sediment transport formula for both catchments, and that each parameter influenced model behaviours differently, with model functions relating to internal geomorphic changes responding in a different way to those relating to the sediment yields from the catchment outlet. The model functions proved useful for providing a way of evaluating the sensitivity of LEMs in the absence of data and methods for an objective function approach.
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-3734
Abstract: & & Gully erosion is recognised as a significant environmental issue. It affects grazing, croplands as well as rangelands. Of particular interest here are mining landscapes which are comprised of unconsolidated waste material that has little or no economic value. These landscapes are new systems with little nutrients and plant growth potential and the materials are often highly erodible and prone to gullying. Many empirical and physical models have been developed to understand gully initiation, growth and stabilisation. Here we demonstrate the use of computer based landscape evolution models to quantify the gully process. These models use a digital elevation model to represent the landform and allow the landform to evolve through time. The models can operate at sub-hourly through to millennial time scales. The landform (and resultant gully) can be visualised and rates of movement quantified and erosion rates calculated. & Different land surface properties such as vegetation cover, armour as well as climate variability can be investigated at the hillslope, catchment and landscape scale. These models offer a huge advance in visualisation and quantification of gully evolution. The models have been used across a wide range of materials and climates and will be demonstrated using several mining case studies. Of particular interest for the mining industry is how surface properties change through time as armouring and weathering occurs and vegetation establishes. Model strengths will be highlighted and areas where advances, particularly field data needs will be discussed.& &
Publisher: Copernicus GmbH
Date: 27-03-2022
DOI: 10.5194/EGUSPHERE-EGU22-6548
Abstract: & & Tailings are a by-product of the processing of minerals at mine sites and are usually fine grained, contain water and processing chemical residues and are usually very erodible. Tailings are commonly stored in & #8216 tailings dams& #8217 and these dams are a feature of many mine sites. These dams are in a geomorphic disequilibrium and have similar risk to that of water storage dams with geotechnical, seismic, hydrological (rainfall) and erosional induced failure concerns. These dams also pose a risk of release of polluted water and the accompanying chemicals and fines.& At the majority of mine sites tailings dams will be permanent geomorphological features which do not geomorphologically integrate with the surrounding landscape. A dam has a design life and it has been suggested that closure designs be considered for a 1000 year design life with other sites considered for 10 000 year scenarios. New methods are therefore needed for assessing long-term behaviour of anthropogenic structures such as tailings dams. Computer based Landscape Evolution Models (LEMs) are a new tool to assess tailings dam design. & These models provide information on type of erosion and erosion location as well as erosion rates. Models such as CAESAR-Lisflood can also provide information on water quality and stream sediment loads and models the transport of all size fractions. The model can therefore provide guidance on long-term behaviour, which allow designs to be tested and improved accordingly. The work uses CAESAR-Lisflood to examines a series of hypothetical tailings dams subject to a range of different possible rainfall scenarios. The findings demonstrate that without maintenance the dam wall will be breached at a time exceeding the dam life design for average conditions but may breach within decades for an extreme (yet possible) event. For both cases water quality will be reduced for centuries post breach and may never reach background (pre breach) levels representing a permanent change in water quality. The modelling here provides a method for the assessment of not just tailings dams but other anthropogenic structures and their geomorphological behaviour. The work here also raises questions about landscape stewardship for such altered systems.& &
Publisher: Wiley
Date: 17-01-2021
DOI: 10.1002/ESP.5060
Publisher: Elsevier BV
Date: 09-2021
Publisher: Copernicus GmbH
Date: 02-2016
DOI: 10.5194/ESURF-2016-4
Abstract: Abstract. Here we study the soilscape (soil-landscape) evolution of a field-site at the semiarid zone of Israel. This region, like similar regions around the world, was subject to intensive loess accumulation during the Pleistocene and early Holocene. Today, hillslopes in this region are dominated by exposed bedrock with deep loess depositions in the valleys and floodplains. The drivers and mechanism that led to this soilscape are unclear. Within this context, we use a soilscape evolution model (mARM5D) to study the potential mechanisms that led to this soilscape. We focus on advancing our conceptual understanding of the processes at the core of this soilscape evolution by studying the effects of fluvial and diffusive sediment transport mechanisms, and the potential effects of climatic and anthropogenic drivers. Our results show that in our field site, dominated by aeolian soil development, hillslope fluvial sediment transport e.g. surface wash and gullies, lead to downslope thinning in soil while diffusive transport e.g. soil creep lead to deeper and more localized soil features at the lower sections of the hillslopes. The results suggest that, in this semiarid, aeolian-dominated and soil depleted landscape, the top section of the hillslopes is dominated by diffusive transport and the bottom by fluvial transport. Temporal variability in environmental drivers had a considerable effect on soilscape evolution. Short but intensive changes during the late Holocene, imitating anthropogenic landuse alterations, rapidly changed the site's soil distribution. This leads us to assume that this region's soil depleted hillslopes are, at least in part, the result of anthropogenic drivers.
Publisher: Wiley
Date: 21-06-2022
DOI: 10.1002/ESP.5423
Abstract: Post‐mining landforms consist of unconsolidated waste, which can be highly erodible. In such structures of loosely bonded material, rill erosion and gully erosion are significant issues that lead to landform degradation. These landforms need to be designed to minimize erosion to ensure long‐term stability and sustainability. Various landform evolution models (LEMs) have been used to predict the evolution of such landforms and identify areas prone to gully erosion. However, there is a degree of uncertainty associated with predictions made by LEMs due to the lack of field data that can be used to assess their accuracy. Here we use the State Space Soil Production and Assessment Model (SSSPAM) to simulate gully erosion on a post‐mining landform. For the first time, we performed a qualitative and quantitative comparison between model predictions and field data of a post‐mining landform using the SSSPAM model. SSSPAM is a coupled soilscape–landform evolution model that simulates fluvial erosion and armouring, diffusive erosion, deposition and physical weathering within the soil profile. Here, two sites on an active coal mine with active gullies evolving in waste rock were examined. In addition, novel methodologies for model calibration based on experimental flume data and model parameter modification procedures for conducting model simulations at different spatial and temporal scales are introduced. Site‐specific erosion parameters, initial landform digital elevation models and the daily rainfall record of the site were used to simulate the evolution of gullies at the two different sites. Results show that SSSPAM can predict the gullies' position and general geomorphic characteristics with a high degree of accuracy.
Publisher: Wiley
Date: 30-04-0270
DOI: 10.1002/ESP.4872
Abstract: When a sediment laden river reaches a flat basin area the coarse fraction of their sediment load is deposited in a cone shaped structure called an alluvial fan. In this article we used the State Space Soil Production and Assessment Model (SSSPAM) coupled landform–soilscape evolution model to simulate the development of alluvial fans in two‐ and three‐dimensional landforms. In SSSPAM the physical processes of erosion and armouring, soil weathering and sediment deposition were modelled using state‐space matrices, in both two and three dimensions. The results of the two‐dimensional fan showed that the fan grew vertically and laterally keeping a concave up long profile. It also showed a downstream fining of the sediments along the fan profile. Both of these observations are in agreement with available literature concerning natural and experimental fan formations. Simulations with the three‐dimensional landform produced a fan with a semicircular shape with concave up long profiles and concave down cross profiles which is typical for fans found in nature and ones developed in laboratory conditions. During the simulation the main channel which brings sediment to the fan structure changed its position constantly leading to the semicircular shape of the fan. This behaviour is similar to the autogenic process of ‘fanhead trenching’ which is the major mechanism of sediment redistribution while the fan is developing. The three‐dimensional fan simulation also exhibited the downstream fining of sediments from the fan apex to the peripheries. Further, the simulated fan also developed complex internal sediment stratification which is modelled by SSSPAM. Currently such complex sediment stratification is thought to be a result of allogenic processes. However, this simulation shows that, such complex internal sediment structures can develop through autogenic processes as well. © 2020 John Wiley & Sons, Ltd.
Publisher: Copernicus GmbH
Date: 18-10-2017
Publisher: Wiley
Date: 19-10-2020
DOI: 10.1002/ESP.5007
Publisher: Elsevier BV
Date: 12-2017
DOI: 10.1016/J.SCITOTENV.2017.04.038
Abstract: Landscape Evolution Modelling (LEM) technologies provide a means by which it is possible to simulate the long-term geomorphic stability of a conceptual rehabilitated landform. However, simulations rarely consider the potential effects of anthropogenic climate change and consequently risk not accounting for the range of rainfall variability that might be expected in both the near and far future. One issue is that high resolution (both spatial and temporal) rainfall projections incorporating the potential effects of greenhouse forcing are required as input. However, projections of rainfall change are still highly uncertain for many regions, particularly at sub annual/seasonal scales. This is the case for northern Australia, where a decrease or an increase in rainfall post 2030 is considered equally likely based on climate model simulations. The aim of this study is therefore to investigate a spatial analogue approach to develop point scale hourly rainfall scenarios to be used as input to the CAESAR - Lisflood LEM to test the sensitivity of the geomorphic stability of a conceptual rehabilitated landform to potential changes in climate. Importantly, the scenarios incorporate the range of projected potential increase/decrease in rainfall for northern Australia and capture the expected envelope of erosion rates and erosion patterns (i.e. where erosion and deposition occurs) over a 100year modelled period. We show that all rainfall scenarios produce sediment output and gullying greater than that of the surrounding natural system, however a 'wetter' future climate produces the highest output. Importantly, incorporating analogue rainfall scenarios into LEM has the capacity to both improve landform design and enhance the modelling software. Further, the method can be easily transferred to other sites (both nationally and internationally) where rainfall variability is significant and climate change impacts are uncertain.
Publisher: Copernicus GmbH
Date: 26-06-2019
Abstract: Abstract. Global agricultural drought policy has shifted towards promoting drought preparedness and climate resilience in favor of disaster relief-based strategies. For this approach to be successful, drought predictability and methods for assessing the many aspects of drought need to be improved. Therefore, this study aims to bring together meteorological and hydrological measures of drought, along with vegetation and soil moisture data to assess how droughts begin, propagate and subsequently terminate for a catchment in eastern Australia. For the study area, thirteen meteorological drought periods persisting more than six months were identified over the last 100 years. During these, vegetation health, soil moisture and streamflow declined, however, all indicators recovered quickly post drought, with no evidence of extended impacts on the rainfall-runoff response, as has been observed elsewhere. Further, drought initiation and propagation were found to be tightly coupled to the combined state of large-scale ocean-atmosphere climate drivers (e.g. El Niño Southern Oscillation, Indian Ocean Dipole and Southern Annular Mode), while termination is caused by persistent synoptic systems (e.g. low-pressure troughs). The combination of climatic factors, topography, soils and vegetation are believed to be what makes the study catchments more resilient to drought than others in eastern Australia. The study ersifies traditional approaches to studying droughts by quantifying catchment response to drought using a range of measures that could also be applied in other catchments globally. This is a key step towards improved drought management.
Publisher: Elsevier BV
Date: 11-2020
Publisher: Copernicus GmbH
Date: 18-10-2017
DOI: 10.5194/GMD-2017-236
Abstract: Abstract. Landscape Evolution Models have a long history of use as exploratory models, providing greater understanding of the role large scale processes have on the long-term development of the Earth’s surface. As computational power has advanced so has the development and sophistication of these models. This has seen them applied at increasingly smaller scale and shorter-term simulations at greater detail. However, this has not gone hand-in-hand with more rigorous verifications that are commonplace in the applications of other types of environmental models- for ex le Sensitivity Analyses. This can be attributed to a paucity of data and methods available in order to calibrate, validate and verify the models, and also to the extra complexity Landscape Evolution Models represent – without these it is not possible to produce a reliable Objective Function against which model performance can be judged. To overcome this deficiency, we present a set of Model Functions – each representing an aspect of model behaviour – and use these to assess the relative sensitivity of a Landscape Evolution Model (CAESAR-Lisflood) to a large set of parameters via a global Sensitivity Analysis using the Morris Method. This novel combination of behavioural Model Functions and the Morris Method provides insight into which parameters are the greatest source of uncertainty in the model, and which have the greatest influence over different model behaviours. The method was repeated over two different catchments, showing that across both catchments and across most model behaviours the choice of Sediment Transport formula was the dominate source of uncertainty in the CAESAR-Lisflood model, although there were some differences between the two catchments. Crucially, different parameters influenced the model behaviours in different ways, with Model Functions related to internal geomorphic changes responding in different ways to those related to sediment yields from the catchment outlet. This method of behavioural sensitivity analysis provides a useful method of assessing the performance of Landscape Evolution Models in the absence of data and methods for an Objective Function approach.
Publisher: Copernicus GmbH
Date: 27-03-2022
DOI: 10.5194/EGUSPHERE-EGU22-2090
Abstract: & & In this study the evolution of a fluvial fan on a synthetic landform under erosion, weathering and deposition was simulated using SSSPAM coupled soil-landscape evolution model. A constant rainfall was simulated on a synthetic landform and a fluvial fan depositional structure was allowed to form at the latter part of the landform. At each time step the geomorphological and particle size distribution information of the fan was recorded. Using this recorded information, the evolutionary characteristics of the fan was studied and compared with experimental and field observation data. Also the surface and subsurface sediment characteristics of the fan were studied. Different fan profile sections were also derived from the recorded data and analysed. The simulation produced a fluvial fan semicircular in shape, with concave up long profiles and convex up cross profiles. The surface sediment sizes of the simulated fan were coarsest near the fan apex and fines toward the fan toe with coarse grained sediment filaments extending radially from the fan apex. These geomorphological features and surface sediment distribution agrees well with field observations of natural fluvial fans. The results of the simulation also show that the fluvial fan develops as a result of the channel bringing sediments in to the fan periodically changing its path due to steepening of channel gradient by sediment deposition. The position of the channel is fixed at the fan apex and the channel path constantly changes along any radial direction form the fan apex. This process is remarkably similar to the process of & #8220 Fan head trenching& #8221 described in literature which is the dominant process in fluvial fan development in the field. Finally, the analysis of fan cross-sections revealed complex sediment layering patterns in the fan profile. The simulation results of SSSPAM coupled soilscape-landscape evolution model provide qualitatively correct geomorphological and sedimentary characterization of the fluvial fan development process.& &
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-4278
Abstract: & & Australia& #8217 s climate is widely recognised as oscillating between drought and flood, with these cycles potentially intensifying under climate change. To reduce the impacts of both, being better prepared for, and more resilient to climate extremes is required . To develop management strategies that address these issues, improved prediction and an understanding of both drought onset and termination is required. Here, a whole-catchment assessment of drought from onset through to propagation and then termination for a 585 km& sup& & /sup& agricultural catchment in eastern Australia was conducted. Meteorological and hydrological measurements of drought were combined with vegetation and soil moisture data to assess how the catchment responded to drought and then recovered during drought termination. Thirteen meteorological drought periods persisting more than six months were identified during this period. During these, vegetation health, soil moisture and streamflow declined, however, all indicators recovered quickly when rainfall surplus returned. Drought onset was tightly coupled to the combined state of large-scale ocean-atmosphere climate drivers and termination was caused by synoptic-scale events. The combination of climatic factors, topography, soils and vegetation are believed to be what makes the study catchments more resilient to drought than others in eastern Australia. The study ersifies traditional approaches to assessing hydrological extremes at the catchment-scale by examining the drought to flood cycle using a range of globally available measures. This is a key step towards improved drought prediction and management.& &
Publisher: Elsevier BV
Date: 05-2019
DOI: 10.1016/J.SCITOTENV.2019.02.097
Abstract: There is considerable debate over how different agricultural management systems such as minimum tillage and grazing affect soil organic carbon (SOC), soil nitrogen (SN) concentrations and soil erosion over the long-term. In this study SOC, SN and erosion characteristics were compared over a ten year period for two neighbouring sites with longstanding but different land management strategies one cropped under a minimum tillage (MT) regime and one used for grazing on largely native pasture. Both sites (Hunter Valley, New South Wales, Australia) shared the same soil type (Euchrozem) and climate. SOC and SN were both found to be ~50% higher at the grazing site while erosion was found to be significantly greater (an order of magnitude) at the cropping site despite the application of MT practices. No discernible link between erosion and either SOC, SN or C:N was evident. While both sites have temporally constant SOC, SN and C:N, the MT site offers scope for increased SOC sequestration.
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-21765
Abstract: & & The water-limited region frequently experiences extreme climate variability.& This region, however, has relatively little hydrological information to characterize the catchment dynamics and its feedback to the climate system. This study assesses the relative benefits of using remotely sensed soil moisture, in addition to sparsely available in-situ soil moisture and stream flow observations, to improve the hydrologic understanding and prediction.& We propose a multi-variable approach to calibrate a hydrologic model, Soil and Water Assessment Tool (SWAT), a semi-distributed, continuous catchment model, with observed streamflow and in-situ soil moisture.& The satellite& span& soil moisture products (~ 5 cm top soil) from the Soil Moisture and Ocean Salinity (SMOS) and the Soil Moisture Active Passive (SMAP) are then used to evaluate the model estimates of soil moisture over the spatial scales through time.& The results show the model calibrated against streamflow only could provide misleading prediction for soil moisture. & Long term in-situ soil moisture observations, albeit limited availability, are crucial to constrain model parameters leading to improved soil moisture prediction at the given site.& & /span& & span& Satellite soil moisture products & /span& & span& rovide useful information to assess simulated soil moisture results across the spatial domains, filling the gap on the soil moisture information at landscape scales.& /span& & span& The preliminary results from this study suggest the potential to produce robust soil moisture and streamflow estimates across scales for a semi-arid region, using a distributed catchment model with in-situ soil network and remotely sensed observations and enhance the overall water budget estimations for multiple hydrologic variables across scales.& & /span& This research is conducted on Merriwa catchment, a semi-arid region located in the Upper Hunter Region of NSW, Australia.& &
Publisher: Wiley
Date: 23-12-2019
DOI: 10.1002/RRA.3558
Publisher: Wiley
Date: 06-07-2021
DOI: 10.1002/ESP.5175
Abstract: Landform evolution models are powerful tools for determining long‐term erosional stability and denudation rates spanning geological timescales. SIBERIA, CAESAR and CHILD are ex les of these model. The newly developed State Space Soil Production and Assessment Model (SSSPAM) coupled soilscape‐landform evolution model has the ability to assess overall erosion rates of catchment scale landforms either using short‐term precipitation events, variable precipitation or time‐averaged precipitation (annual average). In addition, SSSPAM has the capability of developing the subsurface soil profile through weathering and armouring. In SSSPAM, physical processes of pedogenesis such as erosion and armouring, diffusion, sediment deposition and weathering are modelled using a state space matrix approach. In this article we simulate the short‐term evolution (100 years) of a proposed post‐mining landform using both SIBERIA and SSSPAM and compare the erosion and sediment output results. For the short‐term simulations SSSPAM's armouring capability was disabled. The models were then used to simulate the evolution of the catchment for 10,000 years. Results demonstrate that the short‐term SSSPAM simulation results compare well with the results from the established landform evolution model SIBERIA. The long‐term armouring disabled SSSPAM simulations produces simulated erosion rates comparable with SIBERIA simulations both of which are similar to upper limit of field measured denudation rates. The SSSPAM simulation using armouring demonstrated that armouring reduced the erosion rate of the catchment by a factor of 4 which is comparable with the lower limit of field measured denudation rates. This observation emphasizes the importance of armouring in long‐term evolution of landforms. Soil profile cross‐sections developed from the same results show that SSSPAM can also reproduce subsurface soil evolution and stratification and spatial variability of soil profile characteristics typically observed in the field.
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-21255
Abstract: & & Irrigated agriculture has been identified as using approximately 72% of water globally. Australia, like many places in the world, is subject to water sharing plans that cross government boarders and are subject to a mixture of management policies. There is a pressing need to develop a method to monitor irrigation water use to aid in water resource assessments and monitoring. This paper aims to test a previously developed method which monitors irrigation water use using remotely sensed observations over the catchment scale, without the need for in-situ observations, ground data or in& #8209 depth knowledge of crops and their planting dates. Using conservative assumptions about agricultural land management practice, irrigation is calculated as Irr=AET-P. The method tests three vegetation indices derived from Landsat 5/7/8 images to calculate crop coefficients (K& sub& c& /sub& ) based on multiple published relationships. These are combined through the FAO56 methodology using gridded rainfall and two reference evapotranspiration (ET& sub& & /sub& ) products to find actual evapotranspiration as AET=ET& sub& & /sub& xK& sub& c& /sub& , providing six ET& sub& & /sub& -K& sub& c& /sub& combinations. Validation data is sourced from Irrigation Infrastructure Operators (IIO) from across the Murray-Darling Basin, Australia which are required to record irrigation water deliveries for billing purposes. The majority of these regions are in arid or semi-arid regions. Data periods used in this study range from 2003/04 to 2016/17. Results indicate this method can effectively assess irrigation water use over a range of catchment sizes from ~6,000 to ~600,000 ha. The best results returned a monthly irrigation RMSE ranging from 1.13 to 2.42 mm/month. Issues arise when regions have a designated low water allocation volume for that season (& %). The allocation percentage is a function of water storage levels, demand and forecasts. Comparisons with the Standardised Precipitation Index (SPI) and Evaporative Stress Index (ESI) show that the proposed method is robust to the rapid onset and short-term droughts. However, its performance was poor during the long term droughts with low water allocation years. The study results during these years has been predominately attributed to water stress in certain crops being undetected, agricultural managers skipping annual crop commodities as well as stock and domestic water use making up larger portions of total water use. This is a limitation of this approach, although when only comparing results in years with greater than 40% allocations, the results improved significantly showing it can monitor water use effectively. When adequate water is available, this approach is able to accurately predict irrigation water use for the sites examined.& &
Publisher: Wiley
Date: 12-2022
DOI: 10.1002/HYP.14770
Abstract: Semi‐arid to temperate south‐east Australian catchments with agricultural landscapes demonstrate unique hydro‐climatic characteristics. Understanding the behaviour of soil moisture over such catchments and the influence of driving factors are crucial for hydrologic, climatic and agricultural applications. However, this is challenging due the complex, non‐linear relationship between these factors and soil moisture, and the lack of long‐term catchment scale data records. To address this, spatial and temporal patterns of soil moisture over two south‐east Australian river catchments (i.e., Krui and Merriwa) and the influence of soil texture, topography, vegetation and rainfall on soil moisture variability were evaluated using a decadal in‐situ dataset. This unique in‐situ soil moisture monitoring network is established over a semi‐arid to temperate catchment representing typical south‐east Australian agricultural landscape and the data record has captured some major climatic events. Time stability of catchment‐scale soil moisture and the potential of predicting catchment mean soil moisture content using one representative station were also examined using a linear regression model. Soil texture was found as the dominating factor driving the spatial variability of soil moisture in the area. The temporal patterns of soil moisture showed a positive agreement with vegetation dynamics and rainfall at topsoil layers (0–5 cm and 0–30 cm). A higher spatial variability of soil moisture was observed during dry catchment conditions compared to wet catchment conditions. The deeper soil layers (30–60 cm and 60–90 cm) showed highly stable soil moisture values, which might be the driving force of the agriculture in the area. A linear regression based prediction model demonstrated a good potential in estimating spatial mean soil moisture content from one representative station. The results are useful in parameterization of soil moisture variability in land surface, climatic and hydrologic models, agricultural applications and in remote sensing of soil moisture.
Publisher: Wiley
Date: 04-10-2021
DOI: 10.1002/ESP.5234
Abstract: Incision as a result of fluvial erosion is an important process to model when simulating landform evolution. For gullies, it is apparent that coupled with the processes that cause incision there must be a range of processes that stop incision. Once started, rills and gullies will grow infinitely without a reduction in support area and/or being arrested by deposition and armouring. Some of these processes have been well studied under the heading of inter‐rill erosion. Other limiting processes are related to the shape of the landform and how downstream deposition areas are linked geomorphically to the upstream gullies. Armouring is also an important process that reduces gully incision and extension, where the gully erodes to bedrock and the resistant base limits further development. Post‐mining landscapes are new surfaces with new materials and provide the opportunity to examine gully initiation, extension and stabilization. The work presented here has largely been driven by the mining industry, where there has been a need to assess erosion over hazardous wastes like mine tailings and low‐level nuclear waste. We demonstrate the usefulness of computer‐based landscape evolution models and the more recent soilscape models (that include both surface and subsurface processes) to understand both fluvial and diffusive processes as well as armouring in a digital elevation model framework (as well as landscape evolution). Landscape evolution models provide insights into complex non‐linear systems such as gullies. A key need is that of field data to parameterize and validate the models. It is argued that current models have more capability than field data available for parameterization and importantly the validation of model outputs.
Publisher: Wiley
Date: 04-02-2019
DOI: 10.1002/ESP.4566
Publisher: Copernicus GmbH
Date: 29-03-2018
Abstract: Abstract. This paper describes the coupling of the State Space Soil Production and Assessment Model (SSSPAM) soilscape evolution model with a landform evolution model to integrate soil profile dynamics and landform evolution. SSSPAM is a computationally efficient soil evolution model which was formulated by generalising the mARM3D modelling framework to further explore the soil profile self-organization in space and time, and its dynamic evolution. The landform evolution was integrated into SSSPAM by incorporating the processes of deposition and elevation changes resulting from erosion and deposition. The complexities of the physically based process equations were simplified by introducing state-space matrix methodology that allows efficient simulation of mechanistically linked landscape and pedogenesis processes for catena spatial scales. The modelling approach and the physics underpinning the modelled processes are described in detail. SSSPAM explicitly describes the particle size grading of the entire soil profile at different soil depths, tracks the sediment grading of the flow, and calculates the elevation difference caused by erosion and deposition at every point in the soilscape at each time step. The landform evolution model allows the landform to change in response to (1) erosion and deposition, and (2) spatial organisation of the co-evolving soils. This allows comprehensive analysis of soil landform interactions and soil self-organization. SSSPAM simulates fluvial erosion, armouring, physical weathering, and sediment deposition. The modular nature of the SSSPAM framework allows integration of other pedogenesis processes in follow-on research projects. This paper presents the initial results of soil profile evolution on a dynamic landform. These simulations were carried out on a simple linear hillslope to understand the relationships between soil characteristics and the geomorphic attributes (e.g. slope, area). Process interactions which lead to such relationships were also identified. The influence of the depth dependent weathering function on soilscape and landform evolution was also explored. These simulations show that the balance between erosion rate and sediment load in the flow accounts for the variability in spatial soil characteristics while the depth dependent weathering function has a major influence on soil formation and landform evolution.
Publisher: Copernicus GmbH
Date: 04-03-2021
DOI: 10.5194/EGUSPHERE-EGU21-8569
Abstract: & & Evaluating the future stability and land denudation rates of natural or anthropogenic landforms is paramount for sustainable land use practices. Landform evolution models can be powerful tools in this endeavour.& In this study we used the well-established landform evolution model SIBERIA and the newly developed coupled soilscape-landform evolution model SSSPAM to simulate the evolution of a proposed post mining landform. SIBERIA uses a cellular digital elevation model to simulate annual average fluvial and diffusive erosion on landforms using annual average precipitation. However it does not simulate the soil profile evolution on the evolving landform. The new SSSPAM coupled soilscape-landform evolution model has the ability to assess the overall erosion rates of catchment scale landforms either using short term precipitation events, variable precipitation or time averaged precipitation rates. In addition, SSSPAM is able to simulate the evolution of the soil profile of the evolving landform using pedogenetic processes such as physical weathering and armouring.& & & & & & & & & & & & & & & To assess the reliability of SSSPAM, model predictions at 100 and 10000 years were compared with SIBERIA predictions at the same times. During the long term (10000yr) simulation the effect of armouring and weathering on the landform evolution was also assessed. The results obtained from these different simulations were compared and contrasted. Comparison of the short term simulations revealed that SSSPAM results compare well with the simulation results of the more established SIBERIA model. Long term simulation showed that SSSPAM simulation results also compares well with SIBERIA simulations while the erosion rates predicted by both models are close to the land denudation rates measured in the field. The soil profile characteristics and channel forms simulated by SSSPAM long term simulations were examined using several landform cross-sections. This analyses revealed that SSSPAM produces deep incised channels with very low soil thickness in upper reaches of the catchment and shallow channels with relatively thick soil layers in the lower reaches of the catchment. These SSSPAM simulated channels match well with the channel forms and distribution of bedrock channels and alluvial channels observed in the field. The analysis of the catchment cross-sections also showed that SSSPAM is capable of reproducing complex subsurface soil evolution and stratification and spatial variability of soil profile characteristics typically observed in the field.& &
Publisher: Copernicus GmbH
Date: 30-01-2017
Abstract: Abstract. Here we study the soilscape (soil-landscape) evolution of a field site in the semiarid zone of Israel. This region, like similar regions around the world, was subject to intensive loess accumulation during the Pleistocene and early Holocene. Today, hillslopes in this region are dominated by exposed bedrock with deep loess depositions in the valleys and floodplains. The drivers and mechanism that led to this soilscape are unclear. Within this context, we use a soilscape evolution model (mARM5D) to study the potential mechanisms that led to this soilscape. We focus on advancing our conceptual understanding of the processes at the core of this soilscape evolution by studying the effects of fluvial and diffusive sediment transport mechanisms, and the potential effects of climatic and anthropogenic drivers. Our results show that, in our field site, dominated by aeolian soil development, hillslope fluvial sediment transport (e.g., surface wash and gullies) led to downslope thinning in soil, while diffusive transport (e.g., soil creep) led to deeper and more localized soil features at the lower sections of the hillslopes. The results suggest that, in this semiarid, aeolian-dominated and soil-depleted landscape, the top section of the hillslopes is dominated by diffusive transport and the bottom by fluvial transport. Temporal variability in environmental drivers had a considerable effect on soilscape evolution. Short but intensive changes during the late Holocene, imitating anthropogenic land use alterations, rapidly changed the site's soil distribution. This leads us to assume that this region's soil-depleted hillslopes are, at least in part, the result of anthropogenic drivers.
No related grants have been discovered for Greg Hancock.