title: A numerical model to simulate the formation and subsequent evolution of tidal channel networks

authors: van Maanen, Barend

subjects: Long-term morphological evolution

abstract: We present a numerical model that simulates morphological change as a result of the interactions between hydrodynamics, sediment transport and bed elevation change. Numerical simulations indicate that these morphodynamic interactions can lead to the initiation of tidal channels and potentially give rise to large-scale channel networks. We perform a sensitivity analysis to show how model outcome is sensitive to the numerical scheme adopted, hydrodynamic and morphological time-steps, and initial bathymetry. Furthermore, the formation of tidal channels and intertidal areas affects both the large-scale flow patterns, as well as the asymmetry between flood- and ebb-tidal currents.

text: A numerical model to simulate the formation and subsequent evolution of tidal channel networks We present a numerical model that simulates morphological change as a result of the interactions between hydrodynamics, sediment transport and bed elevation change. Numerical simulations indicate that these morphodynamic interactions can lead to the initiation of tidal channels and potentially give rise to large-scale channel networks. We perform a sensitivity analysis to show how model outcome is sensitive to the numerical scheme adopted, hydrodynamic and morphological time-steps, and initial bathymetry. Furthermore, the formation of tidal channels and intertidal areas affects both the large-scale flow patterns, as well as the asymmetry between flood- and ebb-tidal currents.

year: 2011

title: Alkali treatment of hemp fibres for the production of aligned hemp fibre mats for composite reinforcement

authors: Sunny, Tom

subjects: Science & Technology

abstract: The main objective of this study was to produce aligned hemp fibre mats from high strength hemp fibres using dynamic sheet forming (DSF). Alkali treatment of hemp fibre was carried out at ambient and high temperature to separate fibres. Single fibre tensile testing was used to assess the tensile properties of the fibres. It was found that the highest tensile properties were exhibited by high temperature treated fibre, whereas the tensile properties exhibited by ambient temperature treated fibre were lower than for untreated fibre. It was also found that fibre granulated after high temperature treatment, was better separated than that granulated before high temperature treatment. This well-separated fibre could successfully be formed into mats using DSF. The orientation of the formed mat was analysed using ImageJ (NIH, USA) software by which the potential of DSF to produce aligned hemp fibre mat was supported. The tensile properties of composite reinforced by these aligned hemp fibre mats were assessed.

text: Alkali treatment of hemp fibres for the production of aligned hemp fibre mats for composite reinforcement The main objective of this study was to produce aligned hemp fibre mats from high strength hemp fibres using dynamic sheet forming (DSF). Alkali treatment of hemp fibre was carried out at ambient and high temperature to separate fibres. Single fibre tensile testing was used to assess the tensile properties of the fibres. It was found that the highest tensile properties were exhibited by high temperature treated fibre, whereas the tensile properties exhibited by ambient temperature treated fibre were lower than for untreated fibre. It was also found that fibre granulated after high temperature treatment, was better separated than that granulated before high temperature treatment. This well-separated fibre could successfully be formed into mats using DSF. The orientation of the formed mat was analysed using ImageJ (NIH, USA) software by which the potential of DSF to produce aligned hemp fibre mat was supported. The tensile properties of composite reinforced by these aligned hemp fibre mats were assessed.

year: 2020

title: Turning a negative into a positive: Aquatic weed harvesting Lake Rotoehu

authors: Mallinson, Richard

abstract: The submerged aquatic weed hornwort (Ceratophyllum demersum) has become widespread through Lake Rotoehu since its establishment in the lake around 2000. This exotic pest plant is surface reaching in large parts of this shallow lake making it a perfect candidate for mechanical harvesting.
As part of the Te Arawa - Rotorua Lakes Programme the Lake Rotoehu Action Plan sets out nutrient reduction targets for nitrogen and phosphorus. Realising these targets is integral if lake water quality is to be restored to the trophic level index (TLI) target for Lake
Rotoehu. Restoration measures have included land use management efforts to arrest nutrient inputs, phosphorus locking through alum dosing, floating wetlands, and most recently the deployment of two aerators. To date the most successful in-lake nutrient reduction method has been mechanical harvest of hornwort.
Aquatic weed harvesting has resulted in reaching a significant portion of the annual nutrient target for the lake catchment. Attaining this level of nutrient removal has manifested in tangible water quality gains in the past few years. Most noticeable is the reduction in cyanobacterial (blue-green) algal blooms which had been prevalent in the lake in summer months. We discuss the practicalities and problems of submerged lake weed harvesting, disposal options, and impacts of this activity on the lake.

text: Turning a negative into a positive: Aquatic weed harvesting Lake Rotoehu The submerged aquatic weed hornwort (Ceratophyllum demersum) has become widespread through Lake Rotoehu since its establishment in the lake around 2000. This exotic pest plant is surface reaching in large parts of this shallow lake making it a perfect candidate for mechanical harvesting.
As part of the Te Arawa - Rotorua Lakes Programme the Lake Rotoehu Action Plan sets out nutrient reduction targets for nitrogen and phosphorus. Realising these targets is integral if lake water quality is to be restored to the trophic level index (TLI) target for Lake
Rotoehu. Restoration measures have included land use management efforts to arrest nutrient inputs, phosphorus locking through alum dosing, floating wetlands, and most recently the deployment of two aerators. To date the most successful in-lake nutrient reduction method has been mechanical harvest of hornwort.
Aquatic weed harvesting has resulted in reaching a significant portion of the annual nutrient target for the lake catchment. Attaining this level of nutrient removal has manifested in tangible water quality gains in the past few years. Most noticeable is the reduction in cyanobacterial (blue-green) algal blooms which had been prevalent in the lake in summer months. We discuss the practicalities and problems of submerged lake weed harvesting, disposal options, and impacts of this activity on the lake.

year: 2015