Robert Wasson - Academia.edu (original) (raw)

Uploads

Papers by Robert Wasson

Gully erosion is a geomorphic threshold phenomenon controlled by different environmental factors ... more Gully erosion is a geomorphic threshold phenomenon controlled by different environmental factors as well as human activities. In this research, we examined the effect of land use on hydraulic flow and the consequent head cut initiation for similar soil conditions using an experimental plot of 15m*0.4m. Results indicated that boundary shear stresses τ cr for gully initiation in rangeland, dry farming and abandoned land are 192, 43 and 174 dyne/cm 2 , respectively, due to the differences in surface vegetation cover. Moreover, the turbulence of flow and soil response to an increase in water depth showed complicated behavior, which could be attributed to the effect of surface micro relief features and land use impacts. Compared to dry farming, the short vegetation cover in the rangeland decreased the effect of ground cover on flow regime. Even after seven years of abandonment, the response of agricultural land to increasing shear stress was similar to that of dry farming, which indicated the low resilience and high erosional susceptibility of soil in dry land environments. The main explanation for dramatic (3-4 fold) variations of τ cr was the vegetation cover and soil surface conditions. In fact, the remarkable decrease of τ cr in dry farming was related to the effect of tillage practice on soil susceptibility and aggregate strength. The findings indicated that a critical shear stress of 35 dyne/cm 2 used in some physically based models for erosion prediction is not appropriate for estimating gully erosion. In addition, the duration of land abandonment has a crucial influence on soil erodibility that has been less considered in erosion models.

Social Science Research Network, 2022

Allied Publishers eBooks, 2002

Hydrology and Earth System Sciences, Jul 28, 2016

A gully as an accelerated erosion process is responsible for land degradation under various envir... more A gully as an accelerated erosion process is responsible for land degradation under various environmental conditions and has been known as a threshold phenomenon. Although the effects of gullying processes have been well documented, few soil erosion models have taken into account the threshold condition necessary for gully development. This research was devoted to determining the effects of land use change on hydraulic threshold condition and stream power of water flow through an in situ experimental flume (15 m × 0.4 m). Results indicated that head cut initiation and detachment rates showed a better correlation to stream power indices than shear stress (τ cr). The threshold unit stream power value (ω u) for head cut initiation in rangeland, abandoned land, and dry farming land was 0.0276, 0.0149, and 4.5 × 10 −5 m s −1 , respectively. Moreover, the micro-relief condition of soil surface and surface vegetation affected the flow regime of discharge and velocity. It is seen that the composite hydraulic criteria of Froude number (Fr) and discharge (Q) can clearly discriminate the land uses' threshold. In fact, the remarkable decrease of τ cr in dry farming was related to the effect of tillage practice on soil susceptibility and aggregate strength. The findings indicated that using the unit steam power index instead of critical shear stress could increase the models' precision for prediction of head cut development. Compared to the Ephemeral Gully Erosion Model (EGEM) equation for critical shear stress, it is important to point out that for modelling of gully erosion, using single soil attributes can lead to an inaccurate estimation for τ cr. In addition, based on the findings of this research, the use of threshold values of τ cr = 35 dyne cm −2 and ω u = 0.4 cm s −1 in physically based soil erosion models is susceptible to high uncertainty when assessing gully erosion.

Palaeogeography, Palaeoclimatology, Palaeoecology, 1979

The use of water in the 'Top End' of Australia is a hot topic, with competing interests a... more The use of water in the 'Top End' of Australia is a hot topic, with competing interests and pressure from drought-ravaged southern Australia. Water is now a potential lightning rod for conflict between economic uses, environmental concerns, and cultural values. This collection of papers comes out of the Charles Darwin Symposium ‘Water in the Top End’, held at Charles Darwin University, Darwin in May 2008, which focussed on the future and explored a range of perspectives on the two questions: What are the opportunities for and constraints on water use? Should we continue to think of the Northern Territory as a frontier with boundless possibilities? There is an obligation on the present to frame the future of water use in the Top End, and this volume provides valuable fuel for this debate. Bob Wasson is the Deputy Vice-Chancellor, Research & International at Charles Darwin University. Educated in earth sciences with a PhD in geomorphology, he is recognised nationally and internationally for research that underpins the management of natural resources.

Palaeogeography, Palaeoclimatology, Palaeoecology, Mar 1, 1982

Policy and Society, 2016

Reliable long-term flood forecasts are needed because floods, among environmental disasters world... more Reliable long-term flood forecasts are needed because floods, among environmental disasters worldwide, do most damage to lives and property, a problem that is likely to increase as climate changes. The objective of this paper is to critically examine scientific approaches to flood forecasting under deep uncertainty and ambiguity as input to flood policy, and to explore alternative approaches to the development of better forecasts along with the necessary organizational support. This therefore a paper on science policy Aleatory (i.e. frequentist) probability estimates have dominated the science, attached to which are irreducible uncertainties. The lower priority given to finding a physical theory of floods means that ambiguity is high, particularly in relation to choosing a probability density function for forecasting. The historical development of flood forecasting is analyzed within the Uncertainty-Ambiguity Matrix of Schrader, S. Riggs, W.M., and Smith, R.P. (1993). Choice over uncertainty and ambiguity in technical problem solving. Journal of Engineering and Technology Management, 10, 13-99 showing that considerable uncertainty and ambiguity exist and are likely to continue. The way forward appears to be a mix of: broadening the information input to forecasts by engaging many disciplines, Bayesian analyses of probabilities, scenario analyses of catastrophic floods based on all available evidence, and adaptive forecasting in the face of climate change.

This is an impoprtant topic and the paper by Martin Bohle is very welcome taht will hopefully spa... more This is an impoprtant topic and the paper by Martin Bohle is very welcome taht will hopefully spark a wider discussion.

Journal of Earth System Science, 2022

Rapidly uplifting Himalaya contributes a huge sediment load that governs the morphological charac... more Rapidly uplifting Himalaya contributes a huge sediment load that governs the morphological characteristics of the rivers draining it and the flood hazards associated with them. Sediment budgeting of the Himalayan rivers has been a challenge in geomorphology due to complex lithotectonic terrains, varied tectonic activity and rainfall distribution, and extremely diverse topography. Such a situation calls for studies of individual catchments where sediment contributions from different lithotectonic and topographic units can be estimated and controls on sediment yield can be determined to inform understanding of local-scale geomorphic processes and hazard management. This study of Baghmati river determines the sediment contributions of the Nepal Himalaya from the Lesser Himalaya (LH) (with crystalline rocks, high relief and low tectonic activity), and the Siwaliks (with soft rocks, low relief and intense tectonic activity). The sediment contributions from the two lithotectonic terrains through time were determined using: (i) geochemical tracers of optically dated alluvial sediments; (ii) an empirical model based on physical processes, and (iii) a decade long record of hydrological data downstream of the mountain front. The key results are: the low-relief (Siwaliks) terrain provides more sediment compared to the LH because of lithology and tectonics and implies that in tectonically active terrains, relief acts as a secondary control on sediment delivery. The contribution of the Siwaliks to the sediments in Himalayan rivers can be significant and should not be ignored.

Australasian Journal of Water Resources, 2020

ABSTRACT Extreme rainfall is projected to increase with climate change, but the impact of climate... more ABSTRACT Extreme rainfall is projected to increase with climate change, but the impact of climate change on floods is uncertain. Infrastructure design based on information available from short gauged time series (typically ~30 – 80 years) may not take account of the full range of possible flood events, or be suitable for identifying non-stationarity. Australian palaeoflood and palaeo-hydroclimate records drawn from a wide variety of natural archives and documentary sources suggest that Australia has been subjected to larger flood events in the past; a pluvial period for eastern Australia in the eighteenth Century is particularly note-worthy. If the current infrastructure is inadequate for past floods, it is unlikely it will adequately mitigate future floods. We discuss how improved awareness, and incorporation, of palaeoflood records in risk estimates could help guide infrastructure planning and design, flood event prediction and inform flood mitigation policy. This is particularly relevant for Australia with its notoriously variable hydroclimate.

Monographiae biologicae, 1986

Geomorphology, Aug 1, 2016

Gully erosion in the seasonally wet tropics of Australia is a major source of sediment in rivers.... more Gully erosion in the seasonally wet tropics of Australia is a major source of sediment in rivers. Stabilization of gullies to reduce impacts on aquatic ecosystems and water storages is a focus for management. However the cause of the gully erosion is poorly understood and so a critical context for soil conservation is missing. It is uncertain if they are the result of post-European cattle grazing or are they much older and related to non-human factors. The causes of riparian gully erosion along a reach of the Victoria River in the semi-arid tropics of Australia were investigated using several methods. Gully complexes were described and characterised by two major components: a Flood

Palaeogeography, Palaeoclimatology, Palaeoecology, Dec 1, 1983

Gully erosion is a geomorphic threshold phenomenon controlled by different environmental factors ... more Gully erosion is a geomorphic threshold phenomenon controlled by different environmental factors as well as human activities. In this research, we examined the effect of land use on hydraulic flow and the consequent head cut initiation for similar soil conditions using an experimental plot of 15m*0.4m. Results indicated that boundary shear stresses τ cr for gully initiation in rangeland, dry farming and abandoned land are 192, 43 and 174 dyne/cm 2 , respectively, due to the differences in surface vegetation cover. Moreover, the turbulence of flow and soil response to an increase in water depth showed complicated behavior, which could be attributed to the effect of surface micro relief features and land use impacts. Compared to dry farming, the short vegetation cover in the rangeland decreased the effect of ground cover on flow regime. Even after seven years of abandonment, the response of agricultural land to increasing shear stress was similar to that of dry farming, which indicated the low resilience and high erosional susceptibility of soil in dry land environments. The main explanation for dramatic (3-4 fold) variations of τ cr was the vegetation cover and soil surface conditions. In fact, the remarkable decrease of τ cr in dry farming was related to the effect of tillage practice on soil susceptibility and aggregate strength. The findings indicated that a critical shear stress of 35 dyne/cm 2 used in some physically based models for erosion prediction is not appropriate for estimating gully erosion. In addition, the duration of land abandonment has a crucial influence on soil erodibility that has been less considered in erosion models.

Social Science Research Network, 2022

Allied Publishers eBooks, 2002

Hydrology and Earth System Sciences, Jul 28, 2016

A gully as an accelerated erosion process is responsible for land degradation under various envir... more A gully as an accelerated erosion process is responsible for land degradation under various environmental conditions and has been known as a threshold phenomenon. Although the effects of gullying processes have been well documented, few soil erosion models have taken into account the threshold condition necessary for gully development. This research was devoted to determining the effects of land use change on hydraulic threshold condition and stream power of water flow through an in situ experimental flume (15 m × 0.4 m). Results indicated that head cut initiation and detachment rates showed a better correlation to stream power indices than shear stress (τ cr). The threshold unit stream power value (ω u) for head cut initiation in rangeland, abandoned land, and dry farming land was 0.0276, 0.0149, and 4.5 × 10 −5 m s −1 , respectively. Moreover, the micro-relief condition of soil surface and surface vegetation affected the flow regime of discharge and velocity. It is seen that the composite hydraulic criteria of Froude number (Fr) and discharge (Q) can clearly discriminate the land uses' threshold. In fact, the remarkable decrease of τ cr in dry farming was related to the effect of tillage practice on soil susceptibility and aggregate strength. The findings indicated that using the unit steam power index instead of critical shear stress could increase the models' precision for prediction of head cut development. Compared to the Ephemeral Gully Erosion Model (EGEM) equation for critical shear stress, it is important to point out that for modelling of gully erosion, using single soil attributes can lead to an inaccurate estimation for τ cr. In addition, based on the findings of this research, the use of threshold values of τ cr = 35 dyne cm −2 and ω u = 0.4 cm s −1 in physically based soil erosion models is susceptible to high uncertainty when assessing gully erosion.

Palaeogeography, Palaeoclimatology, Palaeoecology, 1979

The use of water in the 'Top End' of Australia is a hot topic, with competing interests a... more The use of water in the 'Top End' of Australia is a hot topic, with competing interests and pressure from drought-ravaged southern Australia. Water is now a potential lightning rod for conflict between economic uses, environmental concerns, and cultural values. This collection of papers comes out of the Charles Darwin Symposium ‘Water in the Top End’, held at Charles Darwin University, Darwin in May 2008, which focussed on the future and explored a range of perspectives on the two questions: What are the opportunities for and constraints on water use? Should we continue to think of the Northern Territory as a frontier with boundless possibilities? There is an obligation on the present to frame the future of water use in the Top End, and this volume provides valuable fuel for this debate. Bob Wasson is the Deputy Vice-Chancellor, Research & International at Charles Darwin University. Educated in earth sciences with a PhD in geomorphology, he is recognised nationally and internationally for research that underpins the management of natural resources.

Palaeogeography, Palaeoclimatology, Palaeoecology, Mar 1, 1982

Policy and Society, 2016

Reliable long-term flood forecasts are needed because floods, among environmental disasters world... more Reliable long-term flood forecasts are needed because floods, among environmental disasters worldwide, do most damage to lives and property, a problem that is likely to increase as climate changes. The objective of this paper is to critically examine scientific approaches to flood forecasting under deep uncertainty and ambiguity as input to flood policy, and to explore alternative approaches to the development of better forecasts along with the necessary organizational support. This therefore a paper on science policy Aleatory (i.e. frequentist) probability estimates have dominated the science, attached to which are irreducible uncertainties. The lower priority given to finding a physical theory of floods means that ambiguity is high, particularly in relation to choosing a probability density function for forecasting. The historical development of flood forecasting is analyzed within the Uncertainty-Ambiguity Matrix of Schrader, S. Riggs, W.M., and Smith, R.P. (1993). Choice over uncertainty and ambiguity in technical problem solving. Journal of Engineering and Technology Management, 10, 13-99 showing that considerable uncertainty and ambiguity exist and are likely to continue. The way forward appears to be a mix of: broadening the information input to forecasts by engaging many disciplines, Bayesian analyses of probabilities, scenario analyses of catastrophic floods based on all available evidence, and adaptive forecasting in the face of climate change.

This is an impoprtant topic and the paper by Martin Bohle is very welcome taht will hopefully spa... more This is an impoprtant topic and the paper by Martin Bohle is very welcome taht will hopefully spark a wider discussion.

Journal of Earth System Science, 2022

Rapidly uplifting Himalaya contributes a huge sediment load that governs the morphological charac... more Rapidly uplifting Himalaya contributes a huge sediment load that governs the morphological characteristics of the rivers draining it and the flood hazards associated with them. Sediment budgeting of the Himalayan rivers has been a challenge in geomorphology due to complex lithotectonic terrains, varied tectonic activity and rainfall distribution, and extremely diverse topography. Such a situation calls for studies of individual catchments where sediment contributions from different lithotectonic and topographic units can be estimated and controls on sediment yield can be determined to inform understanding of local-scale geomorphic processes and hazard management. This study of Baghmati river determines the sediment contributions of the Nepal Himalaya from the Lesser Himalaya (LH) (with crystalline rocks, high relief and low tectonic activity), and the Siwaliks (with soft rocks, low relief and intense tectonic activity). The sediment contributions from the two lithotectonic terrains through time were determined using: (i) geochemical tracers of optically dated alluvial sediments; (ii) an empirical model based on physical processes, and (iii) a decade long record of hydrological data downstream of the mountain front. The key results are: the low-relief (Siwaliks) terrain provides more sediment compared to the LH because of lithology and tectonics and implies that in tectonically active terrains, relief acts as a secondary control on sediment delivery. The contribution of the Siwaliks to the sediments in Himalayan rivers can be significant and should not be ignored.

Australasian Journal of Water Resources, 2020

ABSTRACT Extreme rainfall is projected to increase with climate change, but the impact of climate... more ABSTRACT Extreme rainfall is projected to increase with climate change, but the impact of climate change on floods is uncertain. Infrastructure design based on information available from short gauged time series (typically ~30 – 80 years) may not take account of the full range of possible flood events, or be suitable for identifying non-stationarity. Australian palaeoflood and palaeo-hydroclimate records drawn from a wide variety of natural archives and documentary sources suggest that Australia has been subjected to larger flood events in the past; a pluvial period for eastern Australia in the eighteenth Century is particularly note-worthy. If the current infrastructure is inadequate for past floods, it is unlikely it will adequately mitigate future floods. We discuss how improved awareness, and incorporation, of palaeoflood records in risk estimates could help guide infrastructure planning and design, flood event prediction and inform flood mitigation policy. This is particularly relevant for Australia with its notoriously variable hydroclimate.

Monographiae biologicae, 1986

Geomorphology, Aug 1, 2016

Gully erosion in the seasonally wet tropics of Australia is a major source of sediment in rivers.... more Gully erosion in the seasonally wet tropics of Australia is a major source of sediment in rivers. Stabilization of gullies to reduce impacts on aquatic ecosystems and water storages is a focus for management. However the cause of the gully erosion is poorly understood and so a critical context for soil conservation is missing. It is uncertain if they are the result of post-European cattle grazing or are they much older and related to non-human factors. The causes of riparian gully erosion along a reach of the Victoria River in the semi-arid tropics of Australia were investigated using several methods. Gully complexes were described and characterised by two major components: a Flood

Palaeogeography, Palaeoclimatology, Palaeoecology, Dec 1, 1983

Environmental Hazards, 2021

As mountain tourism rapidly expands in remote landscapes, there is a critical need for improved d... more As mountain tourism rapidly expands in remote landscapes, there is a critical need for improved disaster risk management to ensure the safety of tourists and industry workers, safeguard infrastructure designed to support tourism and service industries (e.g., transportation), as well as protect the local economies that have come to depend on tourism revenue. Drawing from recent disasters in the Himalaya, we present evidence that the promotion of safe and sustainable tourism is out of sync with the proliferation of inbound tourists who are prone to many types of environmental hazards. The key driver of this situation is commercialisation. Other factors include increased mobilities/ access of tourists who are often unaware of or ill-prepared to cope with hazards; lack of regulations with respect to overcrowding, safety and building codes increased exposure to climate change phenomena; and limited disaster response capabilities, including responsibility at the local level. In this perspective we argue that this particularly complex situation is best addressed through the lens of a dynamic system, whereby strong leadership, increased regulation of access and participation, and enhanced professionalism via training are key leverage points in countering uncontrolled commercialisation that drives increased risk to known hazards. The inclusion of tourism into disaster risk management systems is also needed where hazard risks and tourist traffic are high, as tourists are part of the transient population who are often unfamiliar with local conditions and ill-prepared to cope with extreme adversity.