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: The effect of reporting errors on the cross-country relationship between inequality and crime

authors: Gibson, John

subjects: crime

abstract: This paper analyzes reporting errors in crime data to see how they impact econometric estimates, particularly of the key relationship between inequality and crime. Criminal victimization surveys of 140,000 respondents in 37 industrial, transition and developing countries are used. Comparing the crimes experienced by these respondents with those reported to the police, non-random and mean-reverting errors are apparent. Time-varying factors affect the propensity of victims to report crimes to the police, undermining the use of country-specific fixed effects as a means of dealing with measurement error in official crime data. These errors substantially attenuate both cross-sectional and panel estimates of the partial correlation between inequality and crime.

text: The effect of reporting errors on the cross-country relationship between inequality and crime This paper analyzes reporting errors in crime data to see how they impact econometric estimates, particularly of the key relationship between inequality and crime. Criminal victimization surveys of 140,000 respondents in 37 industrial, transition and developing countries are used. Comparing the crimes experienced by these respondents with those reported to the police, non-random and mean-reverting errors are apparent. Time-varying factors affect the propensity of victims to report crimes to the police, undermining the use of country-specific fixed effects as a means of dealing with measurement error in official crime data. These errors substantially attenuate both cross-sectional and panel estimates of the partial correlation between inequality and crime.

year: 2008

title: Research and development absorptive capacity: a Māori perspective

authors: Ruckstuhl, Katharina

subjects: computer science

abstract: This paper presents a view of research and development absorptive capacity from a Māori perspective. The assessment is part of a case study of a longitudinal programme – Science for Technological Innovation: Kia kotahi mai – Te Ao Putaiao me te Ao Hanagarau that aims to increase Aotearoa New Zealand’s capacity to use sci-tech for economic benefit. The paper finds that while Aotearoa New Zealand’s macro policy and meso institutional levels have become more responsive to Māori research and development demands, at the micro level of the individual or the firm there are still constraints given the small numbers of Māori in science, technology, engineering and mathematics. In response to this, a novel model of Māori sci-tech capacity is under development that considers not only research and development technical capacities, but also the human and relational capacities required to accelerate absorptive capacity to respond to Māori social and economic aspirations.

text: Research and development absorptive capacity: a Māori perspective This paper presents a view of research and development absorptive capacity from a Māori perspective. The assessment is part of a case study of a longitudinal programme – Science for Technological Innovation: Kia kotahi mai – Te Ao Putaiao me te Ao Hanagarau that aims to increase Aotearoa New Zealand’s capacity to use sci-tech for economic benefit. The paper finds that while Aotearoa New Zealand’s macro policy and meso institutional levels have become more responsive to Māori research and development demands, at the micro level of the individual or the firm there are still constraints given the small numbers of Māori in science, technology, engineering and mathematics. In response to this, a novel model of Māori sci-tech capacity is under development that considers not only research and development technical capacities, but also the human and relational capacities required to accelerate absorptive capacity to respond to Māori social and economic aspirations.

year: 2019