The Mekong River Delta is one of the world's largest deltas and plays an important role in Vietnam's economic development. Studies of flood propagation over the whole delta have been rare. In 2000, due to global climate change and La Niña phenomenon, the hydrological and meteorological situations were very complicated around the world in general, and in the Mekong River basin in particular. In Mekong Delta, flood occurred early and had two peaks in which the second peak was one of the highest in the past 80 years. This flood caused water levels in the upstream Mekong River basin to become about 1 to 3m higher than the third warning level, and caused extremely severe inundation downstream. In Vietnam, this flood caused damage totaling about 5, 000 billion VN dong (about 4 million US dollars at that time), and its level was used to consider the design elevation of flood control embankments. Thus, through study of this flood is necessary to mitigate flood damage and human suffering and to contribute to policy making and create the conditions for embankment elevation design. In this paper, analysis of the main characteristics of the flood of 2000 was carried out based on the observed data since 1926. Also, simulations were conducted using hydraulic models with topographical, hydrological and meteorological data. The flood simulations using hydraulic model for Vietnamese part of delta were carried out, especially for Dong Thap Muoi and Long Xuyen quadrant to analyze (1) how the flood was distributed spatially and temporally, (2) how long each inundation depth lasted, (3) the extent of the area of the flood, and (4) the effect of flood on paddy fields in 2000. The observed data and simulated results show that this flood was extremely large and complicated, causing severe inundation with the depth of 2.5m lasting more than one month from mid-September to mid-October. Flood in August affected strongly the summer-autumn crop paddy field. The area inundated to the depth of 2.5m was more than one thousand km2.
This study analyzes three borehole cores to examine the sedimentary facies of the extensive floodplain of the Mekong River in Cambodia and discusses the relationship between sedimentary facies and surface topography. Sedimentary facies vary according to surface topographic features on the floodplain. Core PA, located near the end of an abandoned channel, records the history of the formation and subsequent filling of the channel during the Holocene. The channel was filled with interlaminated sand and mud overlain by grayish brown to dull reddish brown stiff mud during the last 4500 years. Core CK was located on the southwestern edge of an area of scroll bars and swales between the Mekong and Bassac rivers. In this core, muddy overbank deposits overlie sandy deposits that probably represent a point bar. The accumulation of the overbank deposits may have started around 2000 cal yr BP. Core TA was obtained from the floodplain along the west bank of the Tonle Sap River. Mottled stiff mud containing granules occurs about 1m below the surface and overlies subangular granules. Muddy overbank deposits corresponding to those of the other two boreholes are not present at the site despite frequent flooding of the Tonle Sap River.
The purpose of this study was to examine the floodplain characteristics of the inner Mekong Delta, on the lower part of the Mekong River in Cambodia. Previous works have not investigated the floodplain characteristics of the fluvial dominated area of the Mekong Delta. To grasp the morphology of the study area, we first constructed topographical profiles from hydrologic maps and Space Shuttle Radar Topography Mission 3 data. Then, focusing on the morphology of the floodplain, we produced a land classification map based on aerial photo interpretation and field survey and identified the morphological structures of the study area. We classified the delta landforms as natural levee, back marsh, abandoned channel, alluvial terrace, swamp, point bar, and artificial landforms, including colmatages. We identified four floodplain zones. Zone A floodplains, along the upper part of the Mekong River, have cut-off point bar patterns. Those in zone B, along the lower part of the Mekong River, are linear, and develop back marsh widely. In zone C, along the Bassac River, the floodplains follow the river meanders, and are characterized by unevenly distributed artificial colmatages. Floodplains in zone D, along the Tonle Sap River, which has an extremely low gradient, display a unique geomorphology caused by seasonally reversed river flows.
The Mekong River is an international river running through 6 countries from China, Myanmar, Lao PDR, Thailand, Cambodia, to Viet Nam. Social strife in this geopolitical region, from decades of wars: the cold war, Viet Nam War, Cambodian civil war and some border conflicts, has taken toll on its people throughout the years. As a result, this region is one of the least developed parts of the world, as reflected in the peoples' low living standards, and in social development. This research introduces the scope of regional cooperation, the geophysical features and socio-economic situation of the Mekong River Basin. The sectors' development possibility and the themes for environmental concern are also introduced. All of these are necessary for the harmony of development and conservation of the basin.
Glacial fluctuations controlled by volcanic events on the Tateyama Volcano (about 2, 670m a. s. l.) in the Hida Range, central Japan, during the last glacial period were reconstructed on the basis of glacial sediments, landforms, volcanic ejecta and their stratigraphic relationships. On Mt. Tateyama (3, 015m a. s. l.) comprising granitic bedrock, glaciers became less extensive depending on the climate change from Murodo Stades I (just before 70ka) and II (just after 70ka) through Tateyama Stades I (just before 29 cal ka), II (18-20ka) and III (10-11ka). In contrast, glaciers on the Tateyama Volcano adjacent to Mt. Tateyama became more expansive from Murodo Stades I and II through Tateyama Stade I, because the successive emergence of lava peaks progressively widened the accumulation area. In addition, a glacier rich in basal water may have surged from a lava peak in Murodo Stade II, due to high geothermal flow. However, it has not been confirmed whether or not the glacier snout descended most in Tateyama Stade I. In Tateyama Stade I, the repeated collapse of caldera walls decreased the accumulation area on the lava peaks, which resulted in intermittent glacial retreat on the volcano. In Tateyama Stades II and III, the glaciers on the volcano advanced to lesser extent depending on the climate change, because the Tateyama Volcano maintained its height and size.
This study examines the rejuvenation of greenhouse horticulture on the Kujukuri Plain in Chiba Prefecture, about 60km from Tokyo. Greenhouse horticulture has gone through many changes since the 1990s, and the management of greenhouse operation, in particular, has changed with the introduction of advanced hydroponics and large agricultural subsidies. The study is based on interviews conducted with farmers, employees of agricultural co-operatives and local government officials in 2005 and 2006, and a land-use survey conducted in 2004. We emphasize actors and their linkages in maintaining horticulture, and examine the formation of the following linkages among actors: the linkages among individual farmers voluntarily involved in farm groups, the linkages among groups of farmers, and those between farmers and agricultural co-operatives, farm equipment manufacturers and local governments. The formation of five hydroponic organizations in Shirako Town is studied by examining several factors that help to maintain and develop greenhouse horticulture. These factors are favourable climate, rich soil, the proximity to large markets, accumulated horticultural technology, advanced infrastructure, the increase in profits and the rationalization of farming owing to the innovations adopted by individual farms, and the improvement in farm working conditions. Among various actors, the leaders of each hydroponic organization and the Shirako Hydroponic Association have played an important role and have been a driving force to develop hydroponic horticulture in Shirako Town. Hydroponic farmers have maintained individual farm management while they have created farm associations that take advantage of working in groups. Moreover, these five hydroponic organizations have improved co-operation with agricultural co-operatives, local government, seedling companies and hydroponic equipment manufacturers.
The purpose of this study was to clarify changes in agricultural production, especially medicinal crop production in Zhengzhang Village, located in the urban shadow of Beijing Metropolis under agricultural structure adjustment. In addition, an analysis is carried out of the reasons that have caused these changes. Through this study, prospects of the developmental trends of agricultural production and farm management in farm households in the urban shadow of Beijing Metropolis are discussed. The P. R. of China (China) started to implement agricultural structure adjustment in 1999. Especially, to face the effects brought by China's entry to the WTO, the Chinese government strengthened the quality control of some agricultural products, which constitute part of China's agricultural structure adjustment. Zhengzhang Village has a tradition of medicinal crop production. Since the introduction of the Reform and Opening Policy, in order to gain more income, farm households have actively developed the business of cultivating and processing medicinal crops. But since 1999, due to the lack of capital to improve processing circumstances, some farm households had to abandon the medicinal crop processing business. Almost simultaneously, some farm households short of agricultural labor abandoned medicinal crop cultivation and transferred to food crop cultivation which provided low but stable income. As a result, in Zhengzhang Village under agricultural structure adjustment, medicinal crop production is diminishing, and income polarization among farm households is becoming obvious. These changes can be mainly attributed to government policy adjustments. Other factors, such as market force, social situation and globalization, also played important roles. This study carried out a detailed field survey of land use and farm management in farm households.
Urban population is increasing in Africa's major cities at a much faster rate than in the rest of the world, leading to dramatic sprawl with associated undesirable environmental and social consequences. Using Nairobi as an example of a major African city, we studied urban growth and addressed the need for urban management tools that can provide perspective scenarios of urban growth. This paper describes land use/cover changes and urban growth modeling for predicting the urban growth of Nairobi city using Cellular Automata (CA), which integrates biophysical factors with dynamic spatial modeling. The model was calibrated and tested using time series of urbanized areas derived from remote sensing imageries, and future growth projected out to 2030. The results show that Nairobi city is experiencing fast spatial expansion with simulated urban land taking up most of the available land within the city and the immediate surroundings. The predicated rapid growth of urban areas has led to an unsustainable sprawled urban growth that has caused major changes to the landscape and loss of vital resource lands. The results show the capability of urban growth modeling in addressing regional planning issues.
Globally, the HIV/AIDS prevalence rates have been higher in the urban areas. The cities, especially in fast urbanizing Sub-Saharan Africa, present conditions that influence the spatial characteristics of health including that of HIV/AIDS. Comprised of migrants from varying socio-cultural backgrounds, and having spatially diverse socio-economic characteristics, the cities are bound to have spatial patterns of the HIV/AIDS epidemic that are as heterogeneous as those at the global, continental, and country levels. This paper reports an endeavour to understand the spatial characteristics of the epidemic through a case study of people living with HIV/AIDS (PLWHA) in Nairobi, Kenya. The study, through a questionnaire survey on PLWHA, established that the AIDS pandemic within the city of Nairobi is spatially heterogeneous. Most of the PLWHA in the study resided in the densely populated administrative locations of the city. These locations are also characterised by high density of people living below the urban poverty line, unhygienic environment, and insecurity. However, the availability of affordable basic living necessities, and the presence of medical, financial and social support, among other reasons, makes these areas the only feasible residential option for most of the PLWHA. Besides these factors, family reunion (and separations due to HIV/AIDS), job-search, HIV/AIDS stigma and discrimination, among other factors, are influencing the spatial distribution of PLWHA through intra-city residential movement and in-migration to Nairobi. The research suggests that addressing economic as well as medical infrastructure would be very important if other mitigation efforts in the spread of HIV are to gain sustainable effects.
Various statistical analyses were conducted to determine the relationship between economic indicators for Chinese provinces and railway freight volume. The results indicated that southeastern coastal areas such as Shanghai and Guangzhou received foreign capital and experienced rapid economic growth in secondary and tertiary industries. On the one hand, railway freight transport is centered on coal production regions like Dongbei and Huabei. In addition, a cluster analysis was performed on the distribution ratio classified by destination province for the railway freight volume from each province. The results indicate that China as a whole can be divided into seven railway freight transport zones such that the freight distribution ratios for destination provinces are similar for neighboring provinces.