title: Effects of low tide rainfall on the erodibility of intertidal cohesive sediments

authors: Pilditch, Conrad A.

subjects: sediment transport

abstract: Low tide rainfall may represent an important but little studied process affecting sediment fluxes on intertidal mudflats. In this study, we simulated rainfall events on an intertidal mudflat (median grain size=18.4 μm) of low slope (1 in 300) then quantified effects on sediment erodibility. Treatments consisted of a high (4.1 mm min⁻¹ for 6 min) and low (0.36 mm min⁻¹ for 60 min) rain intensity, chosen to match naturally occurring events and experiments were conducted seasonally (May and August) to encompass variations in ambient sediment stability. Changes in bed elevation due to rainfall were estimated using marked rods and sediment erodibility parameters (mass of sediment eroded at a flow velocity of 0.3 m s⁻¹ (ME-30, g m⁻²) and critical erosion velocity (Ucrit, m s⁻¹)) were determined in annular flumes (bed area=0.17 m²). Ambient/control sediment erodibility in May (ME-30=211 g m⁻², Ucrit=0.18 m s⁻¹) was higher than in August (ME-30=30 g m⁻², Ucrit=0.26 m s⁻¹) and was correlated with changes in biological activity. In May, surface sediment was influenced by high densities of the bioturbating snail Hydrobia ulvae (1736 ind. m⁻²) and low biomass of the sediment stabilising microphytobenthos (5.7 μg chlorophyll a cm⁻²). In contrast, in August H. ulvae densities were low (52 ind. m⁻²) and microphytobenthic biomass higher (9.2 μg chlorophyll a cm⁻²). The high rain treatment caused a decrease in bed elevation of between 1.5 mm (May) and 4.4 mm (August) and significantly reduced sediment organic content and microphytobenthic biomass. Rainfall increased sediment erodibility; compared to ambient sediments ME-30 increased by a factor of 1.4× in May and 8.8× in August and caused a 10–30% decline in Ucrit. The seasonal difference in treatment effect was due to the change in ambient sediment stability. The low rain treatment in August had no effect on bed elevation, microphytobenthic biomass or sediment erodibility. In May, the same treatment caused a reduction in bed elevation (0.5 mm) and microphytobenthic biomass but counter-intuitively, a decrease in sediment erodibility (ME-30 was reduced by 40%, Ucrit increased by 5%) compared to controls. We attribute this result to removal by rainfall of easily eroded surface flocs and biogenic roughness which resulted in an underlying sediment with a smoother surface and greater resistant to erosion. Results suggest that high intensity rain events may destabilise intertidal sediments making them more susceptible to erosion by returning tidal currents and that the sediment eroded during such events may represent a considerable fraction (up to 25%) of the seasonal variation in shore elevation. The impact of natural rain events are likely to vary considerably due to variations in droplet size, intensity and duration and the interaction with ambient sediment stability

text: Effects of low tide rainfall on the erodibility of intertidal cohesive sediments Low tide rainfall may represent an important but little studied process affecting sediment fluxes on intertidal mudflats. In this study, we simulated rainfall events on an intertidal mudflat (median grain size=18.4 μm) of low slope (1 in 300) then quantified effects on sediment erodibility. Treatments consisted of a high (4.1 mm min⁻¹ for 6 min) and low (0.36 mm min⁻¹ for 60 min) rain intensity, chosen to match naturally occurring events and experiments were conducted seasonally (May and August) to encompass variations in ambient sediment stability. Changes in bed elevation due to rainfall were estimated using marked rods and sediment erodibility parameters (mass of sediment eroded at a flow velocity of 0.3 m s⁻¹ (ME-30, g m⁻²) and critical erosion velocity (Ucrit, m s⁻¹)) were determined in annular flumes (bed area=0.17 m²). Ambient/control sediment erodibility in May (ME-30=211 g m⁻², Ucrit=0.18 m s⁻¹) was higher than in August (ME-30=30 g m⁻², Ucrit=0.26 m s⁻¹) and was correlated with changes in biological activity. In May, surface sediment was influenced by high densities of the bioturbating snail Hydrobia ulvae (1736 ind. m⁻²) and low biomass of the sediment stabilising microphytobenthos (5.7 μg chlorophyll a cm⁻²). In contrast, in August H. ulvae densities were low (52 ind. m⁻²) and microphytobenthic biomass higher (9.2 μg chlorophyll a cm⁻²). The high rain treatment caused a decrease in bed elevation of between 1.5 mm (May) and 4.4 mm (August) and significantly reduced sediment organic content and microphytobenthic biomass. Rainfall increased sediment erodibility; compared to ambient sediments ME-30 increased by a factor of 1.4× in May and 8.8× in August and caused a 10–30% decline in Ucrit. The seasonal difference in treatment effect was due to the change in ambient sediment stability. The low rain treatment in August had no effect on bed elevation, microphytobenthic biomass or sediment erodibility. In May, the same treatment caused a reduction in bed elevation (0.5 mm) and microphytobenthic biomass but counter-intuitively, a decrease in sediment erodibility (ME-30 was reduced by 40%, Ucrit increased by 5%) compared to controls. We attribute this result to removal by rainfall of easily eroded surface flocs and biogenic roughness which resulted in an underlying sediment with a smoother surface and greater resistant to erosion. Results suggest that high intensity rain events may destabilise intertidal sediments making them more susceptible to erosion by returning tidal currents and that the sediment eroded during such events may represent a considerable fraction (up to 25%) of the seasonal variation in shore elevation. The impact of natural rain events are likely to vary considerably due to variations in droplet size, intensity and duration and the interaction with ambient sediment stability

year: 2008

title: Absorptive capacity and internationalization of New Zealand high-tech SMEs in the agro-technology sector

authors: Sedoglavich, Vesna

subjects: absorptive capacity

abstract: This study investigates the relationships between firm's technology, absorptive capacity and the internationalization process in the high-tech SMEs. The research identifies the most influential factors that affect the international activities and expansion decisions of New Zealand high-tech SMEs with core capabilities in agro-technology.

Mixed methods, qualitative and quantitative elements in the data collection and analysis, were employed in this research for a reason that a deeper understanding of the research subject and the analysis of complex issues such as the internationalization process and absorptive capacity required methodological variety. The use of qualitative and quantitative methods took place in parallel. Both methods were used to study the same subject but they had specific objective related purposes and they offered the possibility of developing rich empirical data as well as a more comprehensive understanding of the subject under the study. 

The findings show that it is absorptive capacity that explains internationalization process, not internationalization process that explains absorptive capacity. The practice of internationalizing is as much a reflection of a firm's absorptive capacity as it is its determinant. The research identifies that high-tech SMEs possess technological and non-core absorptive capacity which in a different way influence firms' strategies. The research suggests that firm's technological capabilities and the advantage of specialized knowledge along with their limited non-core absorptive capacity act as constraints to the development of the future international strategy in high-tech SMEs.

The study expands the existing literature on internationalization by developing variables for evaluating absorptive capacity in firms. This helped develop an absorptive capacity model which can be used as a valuable tool for self-assessment by firms to facilitate gaining insight towards further growth and development. The research suggested that if firms were able to measure its absorptive capacity this may result in improved business activities and enhanced presence in the world market. 

The results of this study should encourage firms to identify, capture and articulate knowledge achieved by their ventures. Managers must develop and nurture skills that ensure effective integration of learning as their firms expand, particularly internationally. These findings and absorptive capacity model offered as a tool should encourage managers to explore when, where, and how to best use firm's resources in the business operations. This is particularly important in regards to the research context (high-tech SMEs) where scientists are managers as well.

text: Absorptive capacity and internationalization of New Zealand high-tech SMEs in the agro-technology sector This study investigates the relationships between firm's technology, absorptive capacity and the internationalization process in the high-tech SMEs. The research identifies the most influential factors that affect the international activities and expansion decisions of New Zealand high-tech SMEs with core capabilities in agro-technology.

Mixed methods, qualitative and quantitative elements in the data collection and analysis, were employed in this research for a reason that a deeper understanding of the research subject and the analysis of complex issues such as the internationalization process and absorptive capacity required methodological variety. The use of qualitative and quantitative methods took place in parallel. Both methods were used to study the same subject but they had specific objective related purposes and they offered the possibility of developing rich empirical data as well as a more comprehensive understanding of the subject under the study. 

The findings show that it is absorptive capacity that explains internationalization process, not internationalization process that explains absorptive capacity. The practice of internationalizing is as much a reflection of a firm's absorptive capacity as it is its determinant. The research identifies that high-tech SMEs possess technological and non-core absorptive capacity which in a different way influence firms' strategies. The research suggests that firm's technological capabilities and the advantage of specialized knowledge along with their limited non-core absorptive capacity act as constraints to the development of the future international strategy in high-tech SMEs.

The study expands the existing literature on internationalization by developing variables for evaluating absorptive capacity in firms. This helped develop an absorptive capacity model which can be used as a valuable tool for self-assessment by firms to facilitate gaining insight towards further growth and development. The research suggested that if firms were able to measure its absorptive capacity this may result in improved business activities and enhanced presence in the world market. 

The results of this study should encourage firms to identify, capture and articulate knowledge achieved by their ventures. Managers must develop and nurture skills that ensure effective integration of learning as their firms expand, particularly internationally. These findings and absorptive capacity model offered as a tool should encourage managers to explore when, where, and how to best use firm's resources in the business operations. This is particularly important in regards to the research context (high-tech SMEs) where scientists are managers as well.

year: 2008

title: Education for sustainability in New Zealand schools: An evaluation of three professional development programmes

authors: Eames, Chris W.

subjects: Education for Sustainability

abstract: This Summary Report summarises an evaluation of three Education for Sustainability (EfS) professional development programmes being funded by the Ministry of Education: the Enviroschools Programme, the National EfS (NEfS) Team and Mātauranga Taiao. It is supported by a more extensive Overview Report (Part One in Related Pages) on the evaluation of these three initiatives and an individual report on each initiative (Parts Two-Four in Related Pages).

text: Education for sustainability in New Zealand schools: An evaluation of three professional development programmes This Summary Report summarises an evaluation of three Education for Sustainability (EfS) professional development programmes being funded by the Ministry of Education: the Enviroschools Programme, the National EfS (NEfS) Team and Mātauranga Taiao. It is supported by a more extensive Overview Report (Part One in Related Pages) on the evaluation of these three initiatives and an individual report on each initiative (Parts Two-Four in Related Pages).

year: 2010