The Clarence River (New South Wales, Australia) was the main transport corridor for the timber an... more The Clarence River (New South Wales, Australia) was the main transport corridor for the timber and sugar cane industries operating in the catchment from the 1860s to the 1970s. Using archaeological, documentary, and oral historical resources we explore some of the anthropogenic impacts of these industries upon the fluvial geomorphology of the lower Clarence River. In particular, the deliberate abandonment of obsolete vessels on the river system is a focus. These discarded former cane and timber barges have been used as erosion control devices in several areas around the Harwood Island sugar mill, resulting in the accumulation of sediments and the establishment of mangrove environments in what were degraded areas.
While water resource managers and river scientists recognize the inherent interconnections among ... more While water resource managers and river scientists recognize the inherent interconnections among hydrology, river structure, biophysical processes and ecological patterns, management of environmental flows still pays insufficient attention to the ecological and geomorphological functionality of particular aspects of the flow regime. Implementation of more natural flow regimes has improved habitat conditions for native species in many moderately impaired rivers but mimicking a natural flow regime in heavily modified riverine landscapes cannot be expected to yield successful ecological outcomes unless such flows trigger functional processes. For example, the restoration of peak flows may not regenerate habitats if the river is starved of sediment or if the river channel is highly confined. High biodiversity is supported when variable flow regimes interact with spatially variable (heterogeneous) river channel and floodplain forms. In contrast, as rivers become homogeneous, biodiversity...
Transactions of the Royal Society of South Australia, 2017
ABSTRACT River banks are an important transition zone between aquatic and terrestrial environment... more ABSTRACT River banks are an important transition zone between aquatic and terrestrial environments. This ecotone is highly vulnerable to natural and anthropogenic disturbances. Bank erosion is a common occurrence along the River Murray. Morphological features reflecting river bank instability form a near-continuous pattern along large tracts of the river. This study investigates the character and extent of bank instability along the Torrumbarry Weir Pool. Over 90% of the bank length in this weir pool was assessed as being actively eroding. Notch development was the dominant instability mechanism and it promoted other forms of bank instability. Erosion notches result from stable water levels and inherent soil instability of the river banks along the weir pool. The character and extent of river bank erosion recorded along this section of the River Murray is an artefact of flow regulation and not a reflection of the natural occurrence of bank erosion in river networks. Water level management in the upstream weir pool has significant implications for the management of river banks along regulated reaches of the River Murray.
Contemporary land use can affect sediment nutrient processes in rivers draining heavily modified ... more Contemporary land use can affect sediment nutrient processes in rivers draining heavily modified watersheds; however, studies linking land use to sediment nutrient processes in large river networks are limited. In this study, we developed and evaluated structural equation models for denitrification and phosphorus retention capacity to determine direct and indirect linkages between current land use and sediment nutrient processes during base flow in the Fox River watershed, WI, USA. A large spatial‐scale dataset used for this study included sediment nitrogen and phosphorus retention measurements and land use information for 106 sites. The structural equation models for the Fox River watershed identified direct links between current land use and in‐stream sediment nutrient processes. Subwatersheds with agricultural land consisting of more natural land cover had lower surface water nitrate concentrations and higher denitrification enzyme activity than subwatersheds with less alternativ...
Journal of Geophysical Research: Biogeosciences, 2019
Rivers affected by anthropogenic nutrient inputs can retain some of the phosphorus (P) load throu... more Rivers affected by anthropogenic nutrient inputs can retain some of the phosphorus (P) load through sediment retention and burial. Determining the influence of land use and management on sediment P concentrations and P retention in fluvial ecosystems is challenging because of different stressors operating at multiple spatial and temporal scales. In this study, we sought to determine how land use and management influenced sediment P concentrations and P retention within a river network draining a watershed modified by mixed land use activities, the Fox River, Wisconsin, USA. Results show that current land use had no detectable effect on sediment P concentrations and only a small potential effect on P retention capacity. However, sites draining predominantly forested areas were associated with riverbed sediments less saturated in P, whereas sites draining mainly agricultural areas were more likely to release sediment‐bound P. Current management actions, including the implementation of...
The Clarence River (New South Wales, Australia) was the main transport corridor for the timber an... more The Clarence River (New South Wales, Australia) was the main transport corridor for the timber and sugar cane industries operating in the catchment from the 1860s to the 1970s. Using archaeological, documentary, and oral historical resources we explore some of the anthropogenic impacts of these industries upon the fluvial geomorphology of the lower Clarence River. In particular, the deliberate abandonment of obsolete vessels on the river system is a focus. These discarded former cane and timber barges have been used as erosion control devices in several areas around the Harwood Island sugar mill, resulting in the accumulation of sediments and the establishment of mangrove environments in what were degraded areas.
While water resource managers and river scientists recognize the inherent interconnections among ... more While water resource managers and river scientists recognize the inherent interconnections among hydrology, river structure, biophysical processes and ecological patterns, management of environmental flows still pays insufficient attention to the ecological and geomorphological functionality of particular aspects of the flow regime. Implementation of more natural flow regimes has improved habitat conditions for native species in many moderately impaired rivers but mimicking a natural flow regime in heavily modified riverine landscapes cannot be expected to yield successful ecological outcomes unless such flows trigger functional processes. For example, the restoration of peak flows may not regenerate habitats if the river is starved of sediment or if the river channel is highly confined. High biodiversity is supported when variable flow regimes interact with spatially variable (heterogeneous) river channel and floodplain forms. In contrast, as rivers become homogeneous, biodiversity...
Transactions of the Royal Society of South Australia, 2017
ABSTRACT River banks are an important transition zone between aquatic and terrestrial environment... more ABSTRACT River banks are an important transition zone between aquatic and terrestrial environments. This ecotone is highly vulnerable to natural and anthropogenic disturbances. Bank erosion is a common occurrence along the River Murray. Morphological features reflecting river bank instability form a near-continuous pattern along large tracts of the river. This study investigates the character and extent of bank instability along the Torrumbarry Weir Pool. Over 90% of the bank length in this weir pool was assessed as being actively eroding. Notch development was the dominant instability mechanism and it promoted other forms of bank instability. Erosion notches result from stable water levels and inherent soil instability of the river banks along the weir pool. The character and extent of river bank erosion recorded along this section of the River Murray is an artefact of flow regulation and not a reflection of the natural occurrence of bank erosion in river networks. Water level management in the upstream weir pool has significant implications for the management of river banks along regulated reaches of the River Murray.
Contemporary land use can affect sediment nutrient processes in rivers draining heavily modified ... more Contemporary land use can affect sediment nutrient processes in rivers draining heavily modified watersheds; however, studies linking land use to sediment nutrient processes in large river networks are limited. In this study, we developed and evaluated structural equation models for denitrification and phosphorus retention capacity to determine direct and indirect linkages between current land use and sediment nutrient processes during base flow in the Fox River watershed, WI, USA. A large spatial‐scale dataset used for this study included sediment nitrogen and phosphorus retention measurements and land use information for 106 sites. The structural equation models for the Fox River watershed identified direct links between current land use and in‐stream sediment nutrient processes. Subwatersheds with agricultural land consisting of more natural land cover had lower surface water nitrate concentrations and higher denitrification enzyme activity than subwatersheds with less alternativ...
Journal of Geophysical Research: Biogeosciences, 2019
Rivers affected by anthropogenic nutrient inputs can retain some of the phosphorus (P) load throu... more Rivers affected by anthropogenic nutrient inputs can retain some of the phosphorus (P) load through sediment retention and burial. Determining the influence of land use and management on sediment P concentrations and P retention in fluvial ecosystems is challenging because of different stressors operating at multiple spatial and temporal scales. In this study, we sought to determine how land use and management influenced sediment P concentrations and P retention within a river network draining a watershed modified by mixed land use activities, the Fox River, Wisconsin, USA. Results show that current land use had no detectable effect on sediment P concentrations and only a small potential effect on P retention capacity. However, sites draining predominantly forested areas were associated with riverbed sediments less saturated in P, whereas sites draining mainly agricultural areas were more likely to release sediment‐bound P. Current management actions, including the implementation of...
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