title: Surf zone currents and influence on surfability

authors: Phillips, David

abstract: Surfing headlands are shallow and exposed coastal features that provide a specific form of breaking wave allowing a board-rider to ride on the unbroken wave face. The seabed shape and refraction of the waves in relation to depth contours provide the greatest influence on the quality of the surf break. The large scale and orientation of the Raglan headland allows only the low frequency swells to refract around the headland to create seven different surfing breaks. Each represents a compartmentalization of the shoreline along the headland. This creates variability in wave and current characteristics depending on the orientation and bathymetry at different locations. This provides not only potential access points through the surf-zone (ie: smaller currents), but greater surfability in a range of conditions that is not possible on small scale headlands.
Headlands with surfing waves can be classified as mis-aligned sections of the coast, where the higher oblique angle of the breaking surf generates strong wave-driven currents. These currents are far greater than that found on coastlines in equilibrium with the dominant swell direction, where comparatively insignificant longshore drift is found. The strength and direction of wave-driven currents in the surf zone can influence the surfability of a break. At a surfing headland strong currents flowing downdrift along the shoreline make it difficult for a paddling surfer to get to the "take-off" location of the break, or maintain position in the line-up. In comparison currents flowing updrift along headlands makes getting "out the back" relatively easy, although surfers can be taken out to sea past the "take-off" point by a fast flowing current.
Field experiments at Raglan, on the west coast of New Zealand have been conducted to measure current speed and direction during a large swell event. Observations of surfers attempting to paddle through the breaking-wave zone, confirms the strength of the wave-driven currents with surfers being swept rapidly down the headland. Results from the experiments at Raglan, have shown strong currents in the inshore breaking wave zone with burst-averaged velocities attaining 0.8 ms-1, and maximum bed orbital velocities of up to 2.0 ms-1. Interestingly, further offshore the currents have been found to flow in a re-circulating gyre back up the headland. Comparisons are made from observations of waves and currents found at other surfing headlands around the world. The effect that strong currents may have on the surfability of artificial surfing reefs needs to be considered in the design process, if the surfing amenity is to be maximised for large surf conditions.

text: Surf zone currents and influence on surfability Surfing headlands are shallow and exposed coastal features that provide a specific form of breaking wave allowing a board-rider to ride on the unbroken wave face. The seabed shape and refraction of the waves in relation to depth contours provide the greatest influence on the quality of the surf break. The large scale and orientation of the Raglan headland allows only the low frequency swells to refract around the headland to create seven different surfing breaks. Each represents a compartmentalization of the shoreline along the headland. This creates variability in wave and current characteristics depending on the orientation and bathymetry at different locations. This provides not only potential access points through the surf-zone (ie: smaller currents), but greater surfability in a range of conditions that is not possible on small scale headlands.
Headlands with surfing waves can be classified as mis-aligned sections of the coast, where the higher oblique angle of the breaking surf generates strong wave-driven currents. These currents are far greater than that found on coastlines in equilibrium with the dominant swell direction, where comparatively insignificant longshore drift is found. The strength and direction of wave-driven currents in the surf zone can influence the surfability of a break. At a surfing headland strong currents flowing downdrift along the shoreline make it difficult for a paddling surfer to get to the "take-off" location of the break, or maintain position in the line-up. In comparison currents flowing updrift along headlands makes getting "out the back" relatively easy, although surfers can be taken out to sea past the "take-off" point by a fast flowing current.
Field experiments at Raglan, on the west coast of New Zealand have been conducted to measure current speed and direction during a large swell event. Observations of surfers attempting to paddle through the breaking-wave zone, confirms the strength of the wave-driven currents with surfers being swept rapidly down the headland. Results from the experiments at Raglan, have shown strong currents in the inshore breaking wave zone with burst-averaged velocities attaining 0.8 ms-1, and maximum bed orbital velocities of up to 2.0 ms-1. Interestingly, further offshore the currents have been found to flow in a re-circulating gyre back up the headland. Comparisons are made from observations of waves and currents found at other surfing headlands around the world. The effect that strong currents may have on the surfability of artificial surfing reefs needs to be considered in the design process, if the surfing amenity is to be maximised for large surf conditions.

year: 2003-06-01

title: A study of the digestion and metabolism of dairy cows differing in susceptibility to bloat

authors: Carruthers, Vicki Robin

abstract: The digestive characteristics of cows of high (HS) or low (LS) susceptibility to bloat were investigated. 

Sixteen HS and 16 LS cows were offered pasture or hay when pregnant but not lactating, and pasture or 75% pasture plus 25% hay when lactating. The susceptibility groups did not differ in voluntary intake or apparent digestibility of dry matter, organic matter, nitrogen or energy on either occasion. LS cows produced more milk of a lower protein content than HS cows but yields of fat, protein and lactose were similar for both susceptibility groups.

Subsequent experiments used 4 or 5 cows of each susceptibility group, each fitted with a fistula in the dorsal rumen and offered diets of hay or pasture.

On 3 of 8 diets offered, non-lactating LS cows had less digesta, measured by removal through the fistula, in the reticulo-rumen before feeding than did HS cows. Increasing or decreasing the quantity of digesta in the reticulo-rumen after feeding correspondingly increased or decreased both the quantity of digesta subsequently lost and the quantity remaining 21 hours after feeding, or before the next feeding, for both HS and LS cows. On all diets LS cows lost less fluid from the reticulo-rumen during feeding and more after feeding, than did HS cows. Altering the concentration of Na in rumen fluid by addition of water or electrolyte solutions did not affect the loss of fluid and DM from the reticulo-rumen of LS cows relative to that of HS cows. When offered 3 pastures differing in maturity, an increase in maturity of the pasture resulted in an increase in the quantity of digesta in the reticulo-rumen before feeding, but HS and LS cows did not differ in quantity of digesta on each of the 3 pastures. The quantity of digesta in the reticulo-rumen was greater in cows when offered a diet of low K:Na ratio than when offered a high ratio diet. On both diets, however, LS cows had less digesta in the reticulo-rumen, a lower concentration of K in plasma and excreted less K in their faeces than HS cows.

Lactating HS and LS cows offered pasture ad libitum did not differ in intakes of dry matter and water, in the quantities of fluid and dry matter in the reticulo-rumen or in the rate of digestion when estimated from the loss of dry matter from nylon bags incubated in the ventral sac of the rumen.

HS and LS cows did not differ in capacity of the reticule-rumen. The rumen fluid dilution rate, estimated using Cr EDTA, was similar for both susceptibility groups in 3 experiments and higher for LS than HS cows in one experiment.

Overall, these studies revealed few differences between HS and LS cows in the parameters measured, except that under some experimental conditions LS cows had less digesta in the reticulo-rumen than did HS cows.

text: A study of the digestion and metabolism of dairy cows differing in susceptibility to bloat The digestive characteristics of cows of high (HS) or low (LS) susceptibility to bloat were investigated. 

Sixteen HS and 16 LS cows were offered pasture or hay when pregnant but not lactating, and pasture or 75% pasture plus 25% hay when lactating. The susceptibility groups did not differ in voluntary intake or apparent digestibility of dry matter, organic matter, nitrogen or energy on either occasion. LS cows produced more milk of a lower protein content than HS cows but yields of fat, protein and lactose were similar for both susceptibility groups.

Subsequent experiments used 4 or 5 cows of each susceptibility group, each fitted with a fistula in the dorsal rumen and offered diets of hay or pasture.

On 3 of 8 diets offered, non-lactating LS cows had less digesta, measured by removal through the fistula, in the reticulo-rumen before feeding than did HS cows. Increasing or decreasing the quantity of digesta in the reticulo-rumen after feeding correspondingly increased or decreased both the quantity of digesta subsequently lost and the quantity remaining 21 hours after feeding, or before the next feeding, for both HS and LS cows. On all diets LS cows lost less fluid from the reticulo-rumen during feeding and more after feeding, than did HS cows. Altering the concentration of Na in rumen fluid by addition of water or electrolyte solutions did not affect the loss of fluid and DM from the reticulo-rumen of LS cows relative to that of HS cows. When offered 3 pastures differing in maturity, an increase in maturity of the pasture resulted in an increase in the quantity of digesta in the reticulo-rumen before feeding, but HS and LS cows did not differ in quantity of digesta on each of the 3 pastures. The quantity of digesta in the reticulo-rumen was greater in cows when offered a diet of low K:Na ratio than when offered a high ratio diet. On both diets, however, LS cows had less digesta in the reticulo-rumen, a lower concentration of K in plasma and excreted less K in their faeces than HS cows.

Lactating HS and LS cows offered pasture ad libitum did not differ in intakes of dry matter and water, in the quantities of fluid and dry matter in the reticulo-rumen or in the rate of digestion when estimated from the loss of dry matter from nylon bags incubated in the ventral sac of the rumen.

HS and LS cows did not differ in capacity of the reticule-rumen. The rumen fluid dilution rate, estimated using Cr EDTA, was similar for both susceptibility groups in 3 experiments and higher for LS than HS cows in one experiment.

Overall, these studies revealed few differences between HS and LS cows in the parameters measured, except that under some experimental conditions LS cows had less digesta in the reticulo-rumen than did HS cows.

year: 1986

title: Uia ngā pou o te whare ask the posts of the whare:  (Re)storying the whare in curriculum

authors: Heaton, Sharyn

subjects: Whare

abstract: This research investigated the construction of whare tapawhā discourses in national curricula since 1999 and (re)presents other Māori perspectives of how a whare (house, building, school of learning, curriculum) can be known. I explored the constitutions and subjectivities of a whare and its relationship to hauora, well-being and its dimensions. The central questions raised in this thesis are how has a whare model of hauora, well-being been signified within dominant education texts, and how could a Māori (re)envisioning of a whare assist future Māori-medium hauora learning area developments? Further elaborations on how a whare can be known and its potential contribution to future hauora learning area developments take priority as a focus within this thesis.
For this study, I developed ngā pou whakaaro, a theoretical, conceptual, and methodological framework characterised by unfolding layers of awareness (and reflection) that I applied when thinking and reading through texts. Texts included primary and secondary literature such as curricula policy, hauora redevelopment wānanga (meetings, discussions) notes, hauora redevelopment video, hauora Ministry of Education milestone reports and interview transcripts. Within these texts, I searched for significations and signifiers of how the whare tapawhā model of hauora, well-being or a whare had been (re)presented. I searched for what was clearly evident and the assumptions made about a whare, and critiqued omissions of what had not yet been said. These gaps provided an opportunity to rewrite and reproduce other texts. 
I initially critiqued dominant representations of the whare tapawhā model of hauora, well-being, as evident in English-medium policy texts. I argue that the whare tapawhā model and its nuances in national curricula and compulsory schooling are not only driven by education imperatives, such as the valuing of the Māori language and knowledge in compulsory schooling, but are also assimilative in that the knowledge presented is simplistic and the understandings align more with Eurocentric ideals of well-being, albeit in the Māori language. I show that simplified significations of a whare in educational discourse shape the fictions that the texts seek to represent.
And then, in reading otherwise (Caputo, 1997, p. 62), I examined other texts about a whare and its nuances beyond what is currently known in curricula. I interviewed two Māori pouako (teachers), one Māori-medium curriculum developer, a health practitioner, a kairongoā (healer), and two tohunga whakairo (master carvers) to draw out the possibilities that exist for (re)presenting another Māori perspective of a whare. This space provided an opportunity to transgress from how the whare tapawhā model of hauora, well-being has been represented in curricula in Aotearoa. 
The main ideas that emerged from the interviews and the process of reflecting on the responses of the poukōrero (interview participants) provoked thinking about the possibilities of how in-depth understandings of a whare could support a (re)envisioning of the potential of a whare in future hauora learning area developments. In order to (re)turn to thinking about the place of mātauranga Māori (Māori ways of knowing), and how a whare can be known and experienced by Māori beyond what is currently (re)presented in curricula, the whare of Mautini Aroaro was examined. 
Representations of a whare may be partial and fragmented, but such representations need to be (re)traced back to their parts and elaborated upon to deepen understandings of the possible contribution that a Māori perspective could offer future Māori-medium hauora learning area re-developments. There is no one way to know a whare, nor does it need to be restricted to pre-determined representations identified in curricula. Through a restoration process, I suggest we engage with people’s experiences of a whare on different terms and (re)claim understandings of a whare as a repository and library for future generations.

text: Uia ngā pou o te whare ask the posts of the whare:  (Re)storying the whare in curriculum This research investigated the construction of whare tapawhā discourses in national curricula since 1999 and (re)presents other Māori perspectives of how a whare (house, building, school of learning, curriculum) can be known. I explored the constitutions and subjectivities of a whare and its relationship to hauora, well-being and its dimensions. The central questions raised in this thesis are how has a whare model of hauora, well-being been signified within dominant education texts, and how could a Māori (re)envisioning of a whare assist future Māori-medium hauora learning area developments? Further elaborations on how a whare can be known and its potential contribution to future hauora learning area developments take priority as a focus within this thesis.
For this study, I developed ngā pou whakaaro, a theoretical, conceptual, and methodological framework characterised by unfolding layers of awareness (and reflection) that I applied when thinking and reading through texts. Texts included primary and secondary literature such as curricula policy, hauora redevelopment wānanga (meetings, discussions) notes, hauora redevelopment video, hauora Ministry of Education milestone reports and interview transcripts. Within these texts, I searched for significations and signifiers of how the whare tapawhā model of hauora, well-being or a whare had been (re)presented. I searched for what was clearly evident and the assumptions made about a whare, and critiqued omissions of what had not yet been said. These gaps provided an opportunity to rewrite and reproduce other texts. 
I initially critiqued dominant representations of the whare tapawhā model of hauora, well-being, as evident in English-medium policy texts. I argue that the whare tapawhā model and its nuances in national curricula and compulsory schooling are not only driven by education imperatives, such as the valuing of the Māori language and knowledge in compulsory schooling, but are also assimilative in that the knowledge presented is simplistic and the understandings align more with Eurocentric ideals of well-being, albeit in the Māori language. I show that simplified significations of a whare in educational discourse shape the fictions that the texts seek to represent.
And then, in reading otherwise (Caputo, 1997, p. 62), I examined other texts about a whare and its nuances beyond what is currently known in curricula. I interviewed two Māori pouako (teachers), one Māori-medium curriculum developer, a health practitioner, a kairongoā (healer), and two tohunga whakairo (master carvers) to draw out the possibilities that exist for (re)presenting another Māori perspective of a whare. This space provided an opportunity to transgress from how the whare tapawhā model of hauora, well-being has been represented in curricula in Aotearoa. 
The main ideas that emerged from the interviews and the process of reflecting on the responses of the poukōrero (interview participants) provoked thinking about the possibilities of how in-depth understandings of a whare could support a (re)envisioning of the potential of a whare in future hauora learning area developments. In order to (re)turn to thinking about the place of mātauranga Māori (Māori ways of knowing), and how a whare can be known and experienced by Māori beyond what is currently (re)presented in curricula, the whare of Mautini Aroaro was examined. 
Representations of a whare may be partial and fragmented, but such representations need to be (re)traced back to their parts and elaborated upon to deepen understandings of the possible contribution that a Māori perspective could offer future Māori-medium hauora learning area re-developments. There is no one way to know a whare, nor does it need to be restricted to pre-determined representations identified in curricula. Through a restoration process, I suggest we engage with people’s experiences of a whare on different terms and (re)claim understandings of a whare as a repository and library for future generations.

year: 2022