title: The vulnerability of Tongatapu coastal zone to local impacts of climate and sea level rise related risks

authors: Lao, Fine Faitehina Tutu'u

subjects: Climate change

abstract: Tongatapu coastal zone vulnerability assessment study was conducted to examine the degree of current and future risks of projected climate change and sea level rise on the coastal zone of the main island of the Kingdom of Tonga-Tongatapu. Inundation, and flooding hazards generated by tropical cyclone storm surges are the common threats to Tongatapu coastal towns and villages because of their low-lying settings. Flooding problems are exacerbated by the social trends of population growth and migration from the outer islands of the Kingdom, to Tongatapu the main island where the capital town of the Kingdom, Nuku'alofa is located. Other threats include beach erosion, saltwater intrusion, and seawater spraying of coastal vegetations and properties. A survey of the local people of Tongatapu, mapping of vulnerable areas with GIS, and using my local knowledge of the island coastal zone were the three methods were used to conduct this study. The main objective of this research was to assess the vulnerability of the coastal zone of Tongatapu to local impacts of inundation and flooding hazards associated with climate and sea-level rise related risks. The results of the survey indicated that more than 95% of the respondents agreed that the coastal zone of Tongatapu is vulnerable to inundation and flooding risks generated by tropical cyclones that visit Tongatapu coastal water every year, based on their recollection, knowledge, and experienced of the past storm events that hit Tongatapu. GIS work showed that those coastal towns and villages of Tongatapu that are located in areas less than 5 meter above sea level are vulnerable to the local impacts of inundation and flooding hazards. It is concluded that the yearly visited tropical cyclones to Tonga that are actually hit Tongatapu coastal zone had increasing the vulnerability of the coastal towns and villages of Tongatapu that are located in areas below 5 meters above sea level to inundation and flooding hazards associated with climate change and sea level rise related risks. Other possible cause might be the gradual uplifted of the south coast of Tongatapu due to ongoing earthquake activities in Tonga since the last 200 years. But in facts more research it has to be done to confirm this argument. The response to the local impacts of inundation and flooding hazards in the coastal zone of Tongatapu should be focused on adaptation, risk and hazard management.

text: The vulnerability of Tongatapu coastal zone to local impacts of climate and sea level rise related risks Tongatapu coastal zone vulnerability assessment study was conducted to examine the degree of current and future risks of projected climate change and sea level rise on the coastal zone of the main island of the Kingdom of Tonga-Tongatapu. Inundation, and flooding hazards generated by tropical cyclone storm surges are the common threats to Tongatapu coastal towns and villages because of their low-lying settings. Flooding problems are exacerbated by the social trends of population growth and migration from the outer islands of the Kingdom, to Tongatapu the main island where the capital town of the Kingdom, Nuku'alofa is located. Other threats include beach erosion, saltwater intrusion, and seawater spraying of coastal vegetations and properties. A survey of the local people of Tongatapu, mapping of vulnerable areas with GIS, and using my local knowledge of the island coastal zone were the three methods were used to conduct this study. The main objective of this research was to assess the vulnerability of the coastal zone of Tongatapu to local impacts of inundation and flooding hazards associated with climate and sea-level rise related risks. The results of the survey indicated that more than 95% of the respondents agreed that the coastal zone of Tongatapu is vulnerable to inundation and flooding risks generated by tropical cyclones that visit Tongatapu coastal water every year, based on their recollection, knowledge, and experienced of the past storm events that hit Tongatapu. GIS work showed that those coastal towns and villages of Tongatapu that are located in areas less than 5 meter above sea level are vulnerable to the local impacts of inundation and flooding hazards. It is concluded that the yearly visited tropical cyclones to Tonga that are actually hit Tongatapu coastal zone had increasing the vulnerability of the coastal towns and villages of Tongatapu that are located in areas below 5 meters above sea level to inundation and flooding hazards associated with climate change and sea level rise related risks. Other possible cause might be the gradual uplifted of the south coast of Tongatapu due to ongoing earthquake activities in Tonga since the last 200 years. But in facts more research it has to be done to confirm this argument. The response to the local impacts of inundation and flooding hazards in the coastal zone of Tongatapu should be focused on adaptation, risk and hazard management.

year: 2007

title: Identifying and classifying broader scale of disaster impacts to better inform disaster management policies and practice

authors: Tennakoon, Kishani

abstract: Disasters are often assessed by factors such as their magnitude, severity and impact on affected communities. Typically, disaster management policies are largely informed by learnings from large-scale disasters. Many studies, however, have shown that cumulative smaller scale disaster impacts have similar outcomes comparable to larger scale disasters. This indirectly contributes to a lack of consistency in and paucity of data related to both smaller-scale disasters and their associated cumulative impacts. This paper argues that greater attention needs to be paid to collecting disaster impact data on a range of disaster-scale events along with their cumulative impacts to better inform disaster management policies and practice. The paper aims to test the hypothesis that a better understanding of a wide range of disaster scale types and their impacts on communities, including small-scale disasters, enables the development of more just, consistent and equitable disaster management policies and practice. Analysing economic costs, evacuation and rainfall data from past flood events that affected Aotearoa-New Zealand over the last three decades, the paper found discrepancies and lack of coherence in disaster data collection and reporting, along with a predominant reliance on rainfall intensity data for disaster risk reduction and planning. The findings also confirmed the importance of identifying economic damages for a range of disaster scales, including those from small-scale disasters. This highlights the need for developing a spectrum to better classify and identify disaster impacts based on various spatial and temporal contexts. The paper concludes by affirming that such database would provide much needed evidence for developing a methodology that enables the identification of the level of disaster impacts; thereby guiding the implementation of more just, consistent and equitable disaster management policies and practice.

text: Identifying and classifying broader scale of disaster impacts to better inform disaster management policies and practice Disasters are often assessed by factors such as their magnitude, severity and impact on affected communities. Typically, disaster management policies are largely informed by learnings from large-scale disasters. Many studies, however, have shown that cumulative smaller scale disaster impacts have similar outcomes comparable to larger scale disasters. This indirectly contributes to a lack of consistency in and paucity of data related to both smaller-scale disasters and their associated cumulative impacts. This paper argues that greater attention needs to be paid to collecting disaster impact data on a range of disaster-scale events along with their cumulative impacts to better inform disaster management policies and practice. The paper aims to test the hypothesis that a better understanding of a wide range of disaster scale types and their impacts on communities, including small-scale disasters, enables the development of more just, consistent and equitable disaster management policies and practice. Analysing economic costs, evacuation and rainfall data from past flood events that affected Aotearoa-New Zealand over the last three decades, the paper found discrepancies and lack of coherence in disaster data collection and reporting, along with a predominant reliance on rainfall intensity data for disaster risk reduction and planning. The findings also confirmed the importance of identifying economic damages for a range of disaster scales, including those from small-scale disasters. This highlights the need for developing a spectrum to better classify and identify disaster impacts based on various spatial and temporal contexts. The paper concludes by affirming that such database would provide much needed evidence for developing a methodology that enables the identification of the level of disaster impacts; thereby guiding the implementation of more just, consistent and equitable disaster management policies and practice.

year: 2024

title: Lake Rotokakahi: The kakahi (Hyridella menziesi) in a general framework of lake health

authors: Butterworth, Joseph

subjects: Rotokakahi

abstract: Lake Rotokakahi is a mesotrophic lake located within the Rotorua Lakes District, North Island, New Zealand. Under the legal guardianship of the Tuhourangi and Ngati Tumatawera tribes of Te Arawa it has remained closed to the public since 1948. 

Lake Rotokakahi was last monitored regularly in 1996 under the Environment Bay of Plenty (EBOP) water quality monitoring programme with only the lake outlet (Te Wairoa Stream) being monitored since that time. Water quality data collected up to 1996 suggests that there may be degradation of water quality in the lake, as indicated by declining levels of dissolved oxygen in the bottom waters.

 Lake Rotokakahi steeped in historical significance, as well as having major cultural and recreational values was well known for its abundant resources and as the name suggests, particularly for its massive supply of the freshwater mussel or kakahi (Hyridella menziesi). Freshwater mussel species worldwide are in decline however little is known on factors controlling kakahi abundance and distribution. 

The overarching objective of this thesis is update water quality data last monitored in Lake Rotokakahi in 1996 while also identifying key environmental variables thought to influence kakahi populations.  This objective is underpinned by a number of aims that include:
 	Establishment of a 12-13 month water quality programme within Lake Rotokakahi so that data is obtained for comparisons with previous water quality data (pre-1997) to allow assessment of whether there have been water quality changes in the lake.
 	Conduct a population survey of the resident kakahi population examining possible environmental factors influencing their populations.
 	Present an oral history of Lake Rotokakahi focusing on its historical significance, water quality, and collection of kairoto (food collected form lakes).

from the 18 September 2006 to 14 September 2007 monthly water sampling was carried out at a mid lake station, the lake outflow and inflow for measures of nutrients, phytoplankton, zooplankton and chlorophyll a. Vertical profiles of temperature dissolved oxygen and chlorophyll fluorescence were also taken on various part of Lake Rotokakahi.

A lengthened period of anoxia in the bottom waters during thermal stratification was recorded with increased levels of chlorophyll a in winter and reduced secchi disk depth indicating an increase in phytoplankton biomass. Nutrient concentrations remain moderate relative to historical data. On going water quality monitoring on Lake Rotokakahi is recommended to further evaluate the extent of which water quality change is occurring. This will provide a better understanding of how Lake Rotokakahi can be best managed to further preserve the lake.

On 1 March and 20 April kakahi were sampled at five sites. Large kakahi densities were distributed predominantly in depths above the hypolimnion. Chlorophyll a fluorescence and dissolved oxygen were found to be the best correlates for kakahi density and biomass respectively. Low dissolved oxygen concentrations in the hypolimnion are thought to restrict kakahi distributions to above the thermocline in periods of hypolimnetic anoxia.

text: Lake Rotokakahi: The kakahi (Hyridella menziesi) in a general framework of lake health Lake Rotokakahi is a mesotrophic lake located within the Rotorua Lakes District, North Island, New Zealand. Under the legal guardianship of the Tuhourangi and Ngati Tumatawera tribes of Te Arawa it has remained closed to the public since 1948. 

Lake Rotokakahi was last monitored regularly in 1996 under the Environment Bay of Plenty (EBOP) water quality monitoring programme with only the lake outlet (Te Wairoa Stream) being monitored since that time. Water quality data collected up to 1996 suggests that there may be degradation of water quality in the lake, as indicated by declining levels of dissolved oxygen in the bottom waters.

 Lake Rotokakahi steeped in historical significance, as well as having major cultural and recreational values was well known for its abundant resources and as the name suggests, particularly for its massive supply of the freshwater mussel or kakahi (Hyridella menziesi). Freshwater mussel species worldwide are in decline however little is known on factors controlling kakahi abundance and distribution. 

The overarching objective of this thesis is update water quality data last monitored in Lake Rotokakahi in 1996 while also identifying key environmental variables thought to influence kakahi populations.  This objective is underpinned by a number of aims that include:
 	Establishment of a 12-13 month water quality programme within Lake Rotokakahi so that data is obtained for comparisons with previous water quality data (pre-1997) to allow assessment of whether there have been water quality changes in the lake.
 	Conduct a population survey of the resident kakahi population examining possible environmental factors influencing their populations.
 	Present an oral history of Lake Rotokakahi focusing on its historical significance, water quality, and collection of kairoto (food collected form lakes).

from the 18 September 2006 to 14 September 2007 monthly water sampling was carried out at a mid lake station, the lake outflow and inflow for measures of nutrients, phytoplankton, zooplankton and chlorophyll a. Vertical profiles of temperature dissolved oxygen and chlorophyll fluorescence were also taken on various part of Lake Rotokakahi.

A lengthened period of anoxia in the bottom waters during thermal stratification was recorded with increased levels of chlorophyll a in winter and reduced secchi disk depth indicating an increase in phytoplankton biomass. Nutrient concentrations remain moderate relative to historical data. On going water quality monitoring on Lake Rotokakahi is recommended to further evaluate the extent of which water quality change is occurring. This will provide a better understanding of how Lake Rotokakahi can be best managed to further preserve the lake.

On 1 March and 20 April kakahi were sampled at five sites. Large kakahi densities were distributed predominantly in depths above the hypolimnion. Chlorophyll a fluorescence and dissolved oxygen were found to be the best correlates for kakahi density and biomass respectively. Low dissolved oxygen concentrations in the hypolimnion are thought to restrict kakahi distributions to above the thermocline in periods of hypolimnetic anoxia.

year: 2008