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Urban morphology is used in many developed countries to classify and manage the dis-tribution of urban functions. In urban planning, it helps to identify the emerging prob-lems and solve the disorder of urban functions. The megacity Ho Chi Minh City has faced many problems with uncontrollable urbanization, urban management and plan-ning. It has received increasing tropical storms and cyclones which caused more heavy rains in recent decades. Rapid urbanization has caused the increase of built-up coverage with disordered typologies, incomplete infrastructure and urban-peripheral instability. In the flooding context, these problems have increased more seriously with flooding impacts and caused uncontrollable planning and management in the city. This study applies the urban morphology method to measure flood impacts on urban functions and develop the adaptive solutions for flooding adaptation for Ho Chi Minh City. The methods in this study are based on applying fractal geometry, GIS and Remote Sensing on large-scale maps for measuring the urban morphology. The land-use map and the building footprints map of 2010 were founded to analyze the distribution of urban areas by high resolution of satellite images and large scale GIS data. The fractal geometry was a setting based on Avenue program of Arcview GIS to measure the urban morphology. This formed a key input for the multi-criteria analysis (MCA) method that investigated the cause of flood impacts and suggested the solution for flooding adapta-tion. In addition, alterations of lakes, ponds and watercourse from 1995 to 2009 were explored. The study showed HCMC had problems on irrational development in residential densi-ties areas and urban functions, and the uneven development of population and residen-tial density between the urban areas: too much in the urban districts (about 300 to 500 persons per hectare per block and coverage ratio 0.7 - 0.9). This pushed the increasing demand on built-up area and filled-up rivers and canals (About 80 percent of original ponds and lakes in inner-center were filled-up in the past; and 63 percent of ponds and lakes have been filled-up in Sub-Districts and new-urban-development areas). It made the imbalance between the permeability of land surface and the run-off water flows; then leads the inundation to increase. This is the main reason for reducing the water-storage capacity in rainy season. Flooding in urban residential area was more im-pacted than in rural residential area, higher level and longer flood time; while flooding in the rainy season due to high tides, heavy rains or both was the emerging and uncon-trollable problems. For flooding adaptation, urban morphology analysis helped to figure out the potential areas in the city could be used for reducing flooding impacts in urban areas. There are many low-density residential areas in above 1.5 meter AMSL areas in the North, Northwest and Northeast areas of the city which could be developed with complete infrastructure and urban services to attract people from high-density residential areas impacted deeply by floods in the center. These potential areas could be the long-term strategic solution to flooding adaptation for HCMC. The results also suggested that some current flooded areas would be re-planned or returned to be the water-storage and permeable areas (such as green parks, ponds and lakes). This re-planning would improve the city landscape and increase the permeable surface, green spaces and open spaces to HCMC. More green spaces, lakes and ponds will also help to reduce the temperature of urban center in the dry season. This adaptation solution would reduce at least 25 percent of current flooded areas in urban center. The protection and constructed restriction of current agricultural areas in peri-urban Districts would maintain the infil-tration and green-tree areas. Furthermore, the complete drainage system would help to reduce better flood for these areas. Finally, fully dredging river and canal system of the city would reduce about 25 to 30 percent of current flooded areas.
Historically as a city situated in a low-lying area a Ho Chi Minh City has been exposed to floods. Ho Chi Minh City is a megacity with uncontrollable urbanization and dynam-ic economies. In recent years, flood has become a serious problem with a multitude of follow-on impacts. It received more heavy rains affected by tropical storms and cy-clones. Further urbanization and future changes in climate are likely to increase flood risks. People have faced the flood impacts on the socioeconomic aspects in recent dec-ades. This study researched on 450 households in different spaces of the inner center (old districts), developed center (urban districts) and new-developing areas (peri-districts) and in different geographical elevations to identify the impacts of flooding in various space and time; and various problems on households’ socioeconomic aspects in flood residential areas. The multi-criteria analyses in GIS and with of the combination SPSS analysis, the sur-veyed households were identified by their location on the topographic map to clarify the flooding reasons and the types of flood in the areas. The 450 households were chosen in flood residential areas and selected in three categories of characteristics: (1) 150 poor households in flood housing areas; (2) 150 poor households in non-flood housing areas; and (3) 150 higher-income households in non-flood housing areas. This disparity was to analyze the different flood impacts on socioeconomic aspects and on household capitals amongst them. The linear regression in SPSS analysis was used to clarify the relation-ships between flood types with space factor (geographical elevation) and time factors (flood months in year, and flood years in residential areas). This test gave the supports to the reliability of the study results. By geographical elevation analysis, flood impacted on the areas in three main types: (1) flood by rain; (2) flood by tide; and (3) flood by both rain and tide. The tidal flood oc-cupied the low-elevation areas; flood by rain invaded the widespread higher-elevation areas; and the mix type of flood occupied the transition areas between flood areas by rain and by tide. Lower land had the deeper flood level, however; many of high-land areas were flooded in this city. Flood in residential areas had caused flood problems on streets, sidewalks (housing pavements), residential drainage system, water supply and electric power. In the poor households of Group One, flood in residential areas impacted their housing areas. To protect housing from flooding, many households had to invest their income for house rising or rebuilding or pavement rising, etc. They also privately invested for repairing or new buying their housing facilities, furniture and other appli-ances. Their income was lost and deficit. To the household capitals analysis, households were impacted more on physical, financial, natural and human capitals. The poor households in Group One had the most vulnerabilities amongst three groups, whilst there was no support from social organizations and government at levels. The household strategies developed in this study are to support people in flood and flood-prone areas conserving their capabilities to achieve the strategic outcome for sustainable develop-ment.
Community-Based Adaptation (CBA) to climate change is a people-centred approach designed for the enablement of communities to collectively develop strategies to respond to local impacts that directly affect their lives and livelihoods. Nevertheless, CBA requires political support and the integration into larger-scale adaptation plans and policies; as the scope of local initiatives is rather small, they cannot substitute national or city-level adaptation efforts, but they may be a supplement as short- or medium-term response measures. Despite the success of single CBA pilot projects, the institutionalisation of CBA and its integration as a bottom-up approach into larger-scale adaptation plans and policies is definitely a challenge: firstly, the potential of CBA is still overlooked by decision-makers and planners; secondly, the decentralisation of decision-making is still underdeveloped in many countries and communities are not yet empowered and enabled to actively participate; and thirdly, there is lack of approaches to 'scale-out' and 'scale-up' successful CBA pilot projects.
Consequently, this doctoral thesis aims at going beyond the work of theorists and focuses on the identification of ways to institutionalise CBA. In the theoretical section of this thesis, an academic concept of CBA is formulated; the scope of CBA is defined and challenges for taking CBA beyond the pilot stage are identified. In a further step, a governance and management concept for the integration of CBA as a bottom-up approach into top-down planning approaches is developed. In order to do that, suitable existing governance and management concepts are identified and transferable concept components are combined.
The first result of this concept development step is an ideal-typical 'CBA Governance Management Model' (CBA-GMM), which combines concepts for a policy instrument and a pro-poor funding mechanism, for a governance approach, based on multi-level and network governance, as well as for a management approach that altogether may theoretically help to enable CBA activities. In a next step, the CBA-GMM is applied to the real case of Vietnam. After the assessment of the political and institutional framework, its strengths, constraints and challenges with regard to the institutionalisation of CBA, an 'Applied CBA Governance Management Model' for Vietnam (CBA-AGMM) is developed, which proposes a concept for the integration of CBA into the strongly hierarchical structure of the Vietnamese administrative and decision-making structure. This doctoral thesis shows that it is theoretically possible to integrate CBA as a bottom-up approach into larger-scale adaptation efforts, while it honestly reflects the constraints for putting it into practice.
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.