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Improvement of flood risk assessment under climate change in Ho Chi Minh City with GIS applications
(2014)
Ho Chi Minh City is the largest city in VN. The city is the most important center of economy, society and culture in the southern region of Vietnam. However, due to characteristics of natural conditions with low topography and borders touch the sea so that since the late 20th century with the rapid economic and urban development there are environmental problems have arisen. One of the problems is flooding issue caused by high tide. With these natural conditions and sea level rise of climate change in the future, Ho Chi Minh City is considered as one of the most affected and damaged cities in the world.
Therefore, many policies have been set out from the national to local levels in Vietnam to prepare for adaptability of impacts and risks of the sea level rise and the climate change. And this has also been considered in Ho Chi Minh City as the development policies of the city authorities have to consider in the context of the sea level rise and the climate change. A number of researches have been conducted to assess the impact of climate change to Ho Chi Minh City in the future. However, these researches are still need to be enhanced further.
The flooding problem is a major issue of the sea level rise in Ho Chi Minh City. And to make a good result, the flood model needs a lot of requirements that ensure fine quality of input data, suitable model and a relied procedure. In the available research, the input data is not really the highest quality in the available context in Ho Chi Minh City. As the flood model is implemented, one of the input data requirements of the model is information detail of elevation in the flooded area. And this is more necessary than in geophysical urban areas such as Ho Chi Minh City. And to assess fully flood risk issues for flooding caused by tidal phenomenon in Ho Chi Minh City, the determination of many characteristics of flood model is very useful for users who need to apply the results of the model for the planning development in Ho Chi Minh City in the future. Besides adopting a uniform environment as GIS for managing all the data of flooding problem and making conditions for the development of decision support systems is very necessary for flood management in the future.
The research has been carried out and its results have been generated on the flood risk assessment associated context of the sea level rise due to climate change with high emissions scenario A1FI in 2030 for the current houses, the population and the land use types. The results have shown a lot of the areas where are inundated in the future with the increasing flooding duration, depth and frequency even though they are not flooded at the current because there are some protective structures. This will be helpful for suggesting a forecast of the development direction to decision makers in Ho Chi Minh City for next time period.
And the last part is the proposal for decision and policy makers, authorities and planners as well. Moreover, the results of this research can be used as the references and the foundations for further researches and so that the problems that Ho Chi Minh City may be encountered due to flood risk caused by climate change to the economic and social aspects of the development in Ho Chi Minh City will encounter. And the problem of adaptation to climate change will be more completed and more thoroughly so that it is to minimize the damage of climate change for the city.
Unlike many areas of the world where agricultural producers exhibit the physical, economic and social resources to moderate, or adapt, subsistence agriculture in the Sudano-Sahel region of Cameroon is seem to be particularly vulnerable to the impacts of climatic variability. This is in part due to the fact that the majority of the population depends on rain-fed agriculture for their livelihood. Adapting to climate change in the subsistence agricultural sector is therefore very imperative in providing food security and concomitantly protecting the livelihood of rural communities. This study examined the patterns of current climatic variables on some selected subsistence staple crops namely; millet and sorghum in the Cameroon´s Sudano-Sahel. It also valorized and documented the community based adaptation strategies used by local farmers to cope with current climate change, explored the constraints and opportunities in adaptation and mitigation that could facilely be integrated and incorporated into policies and programs. The guiding premises were that climatic change impacts subsistence crop yields as the lower the rainfall, the higher the vulnerability of the yields of staple crops. It also hypothesized that the present community-based strategies used by the local farmers are relevant and crucial to the present day quest for climate change adaptation strategies. Analyses of agricultural droughts using the Standardized Precipitation Index (SPI), spatio-temporal land use and land cover dynamics via remote sensing were utilized as well as the application of statistical tools for the investigation of pressure and state indicators. A participatory research approach was used in exploring adaptation patterns perceived by the ruralites in the face of variable climatic condition via administered questionnaires. The results suggested critical impact asymmetries due to climatic and socio-economic factors affected subsistence crops in the Sudano-Sahel of Cameroon. Furthermore, SPI results indicated incidences of droughts; with the Multilinear Regression (MLR) models showing temperature and rainfall to an extent determined agricultural crop productivity in the Sudano-Sahel. However, other factors such as population growth have undoubtedly caused enormous impacts on the agricultural system as seen in remote sensing analyses. Questionnaire survey findings also connoted that subsistence farming communities have a rich repertoire of strategies ranging from changing of planting dates, changing of crop varieties, switching from crops to livestock, use of local indicators, movement from rural to urban areas, increment in cultivated lands, irrigation soil conservation practices among many others as they perceive varying climatic conditions. Additionally, some of these indigenous strategies are inherent in ecological agricultural practices that offer a win-win scenario for the simultaneously tackling of climate change adaptation and mitigation and hence meeting the development goals. The results further highlighted the lack of money, poor access to climate information, the encroachment of desert and shortage of man power as some of the factors hindering subsistence farmers’ ability to adapt. The study concluded that adaptation measures in subsistence agriculture were highly significant for poverty reduction, thus improving on the well-being of the ruralites. The key to the ability of farmers to adapt would be access to relevant knowledge and information. Following the rich repertoire of strategies by local farmers, adaptation needed to be mainstreamed and institutional networks strengthened in order for effective community based adaptation.
Central Africa is a band of land stretching from the Atlantic Ocean to the Horn of Africa between 18º N 0.75º S and 18º W 44º E. The climate of this region shows a transition zone from the Sahara Desert in the north to the wet tropical Guinean coast and equatorial continental interior in its south. In such transition zones, drought is a common occurrence; of great concern is the progressive drying of the region from the 1970s and into the 1980s. This thesis aims to investigate whether climate change has occurred in Central Africa in the 2nd half of the 20th century. The reanalysis data from the National Centres for Environmental Prediction (NCEP) was used to analyse trends of temperature and precipitation over Central Africa with the linear regression model and patterns of precipitation using principal component analysis. The results of the trend analyses revealed an average increase in temperature of 0.15K/ decade and an average decrease in precipitation of -91 mm/decade for the period 1948-2004 over the whole study area. A regional trend analysis of box averaged data (2.5° in latitude and longitude) revealed an increased precipitation over the Northern part,” the Sahel”, and a marked decrease in precipitation and an increase in temperature over the Eastern parts of the study areas especially in countries such as Somalia, Sudan and Ethiopia. To quantify the changes in temperature and precipitation for different climatic periods (1951-1980, 1961-1990 and 1971-2000), 30-year trend analyses were also performed. Results revealed a relatively stable temperature trend and fluctuations in the precipitation trend over the three 30 year climate periods. Principal component analysis produces a decomposition of the data field into spatial patterns (eigenvectors) and a temporal time series describing the temporal importance of these patterns. For precipitation over Central Africa, three patterns stand out for 60.39% of the total variance in the precipitation over Central Africa. The individual principal components explain 37.6%, 12.1%, and 10.7% respectively of the total variance. The first principal component captures progressive drying in Central Africa, the second principal component captures the different seasons within Central Africa and the third principal component captures the movement of the Intertropical Convergence Zone over Central Africa. Apart from explaining the current precipitation patterns over Central Africa, the use of principal component analysis in this study has demonstrated that a limited number of spatial patterns are basis for African weather, coordinate system for present day climate with maximum variance contribution along the first axis, maximum of the remaining variance along the second axis with subsequent axes explaining less variance can be used to explain precipitation variability within Central Africa. The same method can be used to explain temporal differences between climate change scenarios and present day climate.