title: Spatial variation of the non-linear interactions between estuarine flooding drivers in Aotearoa New Zealand

authors: Langer Costa, Wagner Luiz

abstract: Coastal flooding is one of the main concerns worldwide associated with climate change.
Historically, coastal cities have regularly experienced hazardous flooding across the globe,
contributing to coastal population vulnerability. In Aotearoa New Zealand, an island nation,
the outlook of rising sea levels is especially concerning due to the number of people that live
in the coastal zone. Predicting extreme water levels is challenging and depends on properly
identifying the main physical processes. Swells, wind waves, storm surges, and astronomical
tides are transformed when propagating inside shallow coastal lagoons, bays and estuaries,
mainly because of their mutual interaction (e.g., phase alteration) but also because of the effects
of constrictions and friction imposed by the estuarine morphology (e.g., amplification and
asymmetry). Furthermore, the compound action of different drivers and extreme events in close
succession can exacerbate flooding. The understanding of non-linear interactions between
flooding drivers can substantially improve the power of prediction of flooding in coastal areas
with complex morphology such as estuaries. For that, proper bathymetry and topography data
are fundamental for assessing flooding risk, which can be challenging because some of the
current acquision methods are economically expensive or not applicable to remote and shallow
areas exposed during low tide. Satellite-derived bathymetry and topography are a recent
approach which are increasingly used to tackle this issue.
Although flooding drivers have already been identified and studied around the coast of
Aotearoa New Zealand, few studies have focused on their interaction inside estuaries. Similarly,
very little has been undertaken on the applicability of satellite-derived elevation data for
hydrodynamic modelling. This thesis regionally assesses the non-linear interactions between
storm surges, waves, astronomical tides and estuarine morphology and the suitability of
satellite-derived data to represent these complex interactions in hydrodynamic models.
The main findings are that tide-surge interactions are a major contributor to the water level
inside estuaries and cannot be neglected when simulating flooding events. Tide-surge
interactions can represent variations in the water level ranging from -16 cm (below mean sea
level) to +27 cm (above mean sea level). In addition, non-linear interactions induced by the
estuarine morphology — especially the coverage of the intertidal zone related to the total
surface area of the estuary — modulate the co-occurrence rate between events outside and
inside an estuary. It was found that co-occurrence rates can vary largely according to the estuary
(20–86%). Furthermore, storm-surge and wave interactions have shown strong potential for
compound and clustering effects in estuaries on the North Island, linked to severe south and
southwesterly winds generated by local weather patterns. Wave height and storm surges
corresponding to extreme water levels are significantly correlated, especially inside estuaries
in locations close to the estuarine entrance. Wind waves are more strongly correlated to storm
surges on the west coast while swell waves show a stronger correlation on the east coast of the
North Island. However, when wind and swell waves are combined (i.e., integrated wave
hindcast data) the correlation between wave heights and storm surges is stronger than when
analysed separately. Furthermore, independent and clustered extreme events of waves and
storm surges follow similar seasonality, can co-occur and can be composed of up to 12 extreme
events occurring within 15 days. Finally, based on existing techniques, a framework was
applied to obtain satellite-derived topo-bathymetric data. Although the applied method is
sensitive to several factors (e.g., the complexity of the relief, number of processed images,
bottom reflection), the derived topographic data showed good approximation to LiDAR data
validation — showing similar accuracy of ~20 cm, in an elevation range of approximately 2m.
The elevation estimates were used in hydrodynamic modelling to assess extreme water levels
in a complex estuarine system, considering non-linear interactions. Simulation scenarios using
only satellite-derived elevations could represent extreme water levels inside an estuary with
complex morphology with comparable accuracy of the scenarios using topo-bathymetric data
acquired using in-situ methods (< 0.1 m difference). The results show that satellite-derived data
can be a good replacement when data originating from traditional methods are scarce or
unavailable.
In conclusion, the thesis shows the regional patterns of non-linear interactions between
different flooding drivers around Aotearoa New Zealand, showing where and when these
interactions are important. Furthermore, it shows how satellite-derived techniques can improve
the power of predicting flooding in remote areas with data scarcity. These findings are crucial
for enhancing the prediction of flooding in morphologically complex areas such as estuaries,
where a great part of the coastal community and civil infrastructure are based and have major
social-economic importance. A better understanding of estuarine flooding would make coastal
adaptation policies more effective by making the current models more accurate.

text: Spatial variation of the non-linear interactions between estuarine flooding drivers in Aotearoa New Zealand Coastal flooding is one of the main concerns worldwide associated with climate change.
Historically, coastal cities have regularly experienced hazardous flooding across the globe,
contributing to coastal population vulnerability. In Aotearoa New Zealand, an island nation,
the outlook of rising sea levels is especially concerning due to the number of people that live
in the coastal zone. Predicting extreme water levels is challenging and depends on properly
identifying the main physical processes. Swells, wind waves, storm surges, and astronomical
tides are transformed when propagating inside shallow coastal lagoons, bays and estuaries,
mainly because of their mutual interaction (e.g., phase alteration) but also because of the effects
of constrictions and friction imposed by the estuarine morphology (e.g., amplification and
asymmetry). Furthermore, the compound action of different drivers and extreme events in close
succession can exacerbate flooding. The understanding of non-linear interactions between
flooding drivers can substantially improve the power of prediction of flooding in coastal areas
with complex morphology such as estuaries. For that, proper bathymetry and topography data
are fundamental for assessing flooding risk, which can be challenging because some of the
current acquision methods are economically expensive or not applicable to remote and shallow
areas exposed during low tide. Satellite-derived bathymetry and topography are a recent
approach which are increasingly used to tackle this issue.
Although flooding drivers have already been identified and studied around the coast of
Aotearoa New Zealand, few studies have focused on their interaction inside estuaries. Similarly,
very little has been undertaken on the applicability of satellite-derived elevation data for
hydrodynamic modelling. This thesis regionally assesses the non-linear interactions between
storm surges, waves, astronomical tides and estuarine morphology and the suitability of
satellite-derived data to represent these complex interactions in hydrodynamic models.
The main findings are that tide-surge interactions are a major contributor to the water level
inside estuaries and cannot be neglected when simulating flooding events. Tide-surge
interactions can represent variations in the water level ranging from -16 cm (below mean sea
level) to +27 cm (above mean sea level). In addition, non-linear interactions induced by the
estuarine morphology — especially the coverage of the intertidal zone related to the total
surface area of the estuary — modulate the co-occurrence rate between events outside and
inside an estuary. It was found that co-occurrence rates can vary largely according to the estuary
(20–86%). Furthermore, storm-surge and wave interactions have shown strong potential for
compound and clustering effects in estuaries on the North Island, linked to severe south and
southwesterly winds generated by local weather patterns. Wave height and storm surges
corresponding to extreme water levels are significantly correlated, especially inside estuaries
in locations close to the estuarine entrance. Wind waves are more strongly correlated to storm
surges on the west coast while swell waves show a stronger correlation on the east coast of the
North Island. However, when wind and swell waves are combined (i.e., integrated wave
hindcast data) the correlation between wave heights and storm surges is stronger than when
analysed separately. Furthermore, independent and clustered extreme events of waves and
storm surges follow similar seasonality, can co-occur and can be composed of up to 12 extreme
events occurring within 15 days. Finally, based on existing techniques, a framework was
applied to obtain satellite-derived topo-bathymetric data. Although the applied method is
sensitive to several factors (e.g., the complexity of the relief, number of processed images,
bottom reflection), the derived topographic data showed good approximation to LiDAR data
validation — showing similar accuracy of ~20 cm, in an elevation range of approximately 2m.
The elevation estimates were used in hydrodynamic modelling to assess extreme water levels
in a complex estuarine system, considering non-linear interactions. Simulation scenarios using
only satellite-derived elevations could represent extreme water levels inside an estuary with
complex morphology with comparable accuracy of the scenarios using topo-bathymetric data
acquired using in-situ methods (< 0.1 m difference). The results show that satellite-derived data
can be a good replacement when data originating from traditional methods are scarce or
unavailable.
In conclusion, the thesis shows the regional patterns of non-linear interactions between
different flooding drivers around Aotearoa New Zealand, showing where and when these
interactions are important. Furthermore, it shows how satellite-derived techniques can improve
the power of predicting flooding in remote areas with data scarcity. These findings are crucial
for enhancing the prediction of flooding in morphologically complex areas such as estuaries,
where a great part of the coastal community and civil infrastructure are based and have major
social-economic importance. A better understanding of estuarine flooding would make coastal
adaptation policies more effective by making the current models more accurate.

year: 2023

title: President’s address 2012

authors: Rowarth, Jacqueline S.

abstract: The conferences, symposia and newsletters that we create are part of the information flow, and are driven by members. The role of NZGA is to assist in improving performance in all aspects of agrifood production. It is the interaction between farmers, researchers, policy analysts and industry personnel that leads to the development of new ideas and resource efficient thinking that makes a difference. That difference will allow New Zealand to have a role in feeding the world through sustainable agricultural production systems. The research and development, technology transfer and farm-enterprise resilience that we have already recognised as being vital for improving agricultural productivity have been highlighted as being vital for the world.

text: President’s address 2012 The conferences, symposia and newsletters that we create are part of the information flow, and are driven by members. The role of NZGA is to assist in improving performance in all aspects of agrifood production. It is the interaction between farmers, researchers, policy analysts and industry personnel that leads to the development of new ideas and resource efficient thinking that makes a difference. That difference will allow New Zealand to have a role in feeding the world through sustainable agricultural production systems. The research and development, technology transfer and farm-enterprise resilience that we have already recognised as being vital for improving agricultural productivity have been highlighted as being vital for the world.

year: 2012

title: What works for midwives supporting māmā through emotional distress?

authors: Roia, Tiaan Mereana Manurangi

abstract: Pregnancy and the postnatal period are particularly vulnerable times for mothers’ mental health, with an increased risk of women experiencing depression and anxiety during this time. Therefore, understanding the level and type of service midwives provide to māmā who experience emotional distress is vital to know what midwives need in order to provide the right care to their clients.
The aim of this study was to find out what tools and resources community-based midwives find most helpful to support the needs of māmā. Seven semi-structured interviews were conducted, including four Māori midwives, who were able to provide insight on their experiences caring for mothers with mental health needs. Overall, the interviews reflected a strong sense of care and empathy from midwives during their time caring for mothers. Midwives appeared to rely on their interpersonal skills and intuition about emotional distress, and emphasised the importance of connecting with people and utilising support from their communities. Whilst midwives were interested and engaged with providing appropriate care to mothers, they were unbeknown to some of the clinical resources that could be available to their clients. The complexity of referrals and access to mental health services was central to the midwives’ frustration around caring for mothers, as well as a lack of education relating to kaupapa Māori, cultural competency, and mental health processes.
Recommendations based on this study are to provide midwives with education and training on topics like kaupapa Māori, on social and mental health resources and processes for referral to increase their ability to support and care for mothers who experience emotional distress. Improvements to the pathways for referrals and access to mental health services is essential. Future research should focus on understanding why midwives aren’t using a range of online apps and tools, and increase awareness of the available modes of support available.

text: What works for midwives supporting māmā through emotional distress? Pregnancy and the postnatal period are particularly vulnerable times for mothers’ mental health, with an increased risk of women experiencing depression and anxiety during this time. Therefore, understanding the level and type of service midwives provide to māmā who experience emotional distress is vital to know what midwives need in order to provide the right care to their clients.
The aim of this study was to find out what tools and resources community-based midwives find most helpful to support the needs of māmā. Seven semi-structured interviews were conducted, including four Māori midwives, who were able to provide insight on their experiences caring for mothers with mental health needs. Overall, the interviews reflected a strong sense of care and empathy from midwives during their time caring for mothers. Midwives appeared to rely on their interpersonal skills and intuition about emotional distress, and emphasised the importance of connecting with people and utilising support from their communities. Whilst midwives were interested and engaged with providing appropriate care to mothers, they were unbeknown to some of the clinical resources that could be available to their clients. The complexity of referrals and access to mental health services was central to the midwives’ frustration around caring for mothers, as well as a lack of education relating to kaupapa Māori, cultural competency, and mental health processes.
Recommendations based on this study are to provide midwives with education and training on topics like kaupapa Māori, on social and mental health resources and processes for referral to increase their ability to support and care for mothers who experience emotional distress. Improvements to the pathways for referrals and access to mental health services is essential. Future research should focus on understanding why midwives aren’t using a range of online apps and tools, and increase awareness of the available modes of support available.

year: 2023