Modélisation hydrologique déterministe pour l'évaluation des risques d'inondation et le changement du climat en grand bassin versant. Application au bassin versant de Vu Gia Thu Bon, Viet Nam.

Climate change due to the increase of greenhouse gas emissions is considered to be one of the major challenges to mankind in the 21st century. It will lead to changes in precipitation, atmospheric moisture, increase in evaporation and probably a higher frequency of extreme events. The consequences of these phenomena will have an influence on many aspects of human society. Particularly at river deltas, coastal regions and developing countries, the impacts of climate change to socio-economic development become more serious. So there is a need for a robust and accurate estimation of the variation of natural factors due to climate change, at least in the hydrological cycle and flooding events to provide a strong basis for mitigating the impacts of climate change and to adapt to these challenges. The aim of this study is to present a methodology to assess the impacts of different climate change scenarios on a flood prone area of a coastal river basin in the central region of Viet Nam – Vu Gia Thu Bon catchment. The hydrological simulations are based on a validated deterministic hydrological model which integrates geology, soil, topography, river systems and climate variables. The present day climate, over the period of 1991-2010 was reasonably simulated by the hydrological model. Future climate (2091-2100) information was obtained from a dynamical downscaling of the global climate models. The study also analyzes the changes in the flood dynamics of the study region, the hydrological shift and the uncertainties of climate change simulation.Le changement climatique dû à l'augmentation des émissions de gaz à effet de serre est considéré comme l'un des principaux défis pour les êtres humains dans 21ème siècle. Il conduira à des changements dans les précipitations, l'humidité atmosphérique, augmentation de l'évaporation et probablement augmenter la fréquence des événements extrêmes. Les conséquences de ces phénomènes auront une influence sur de nombreux aspects de la société humaine. Donc, il y a une nécessité d'avoir une estimation robuste et précise de la variation des facteurs naturels dus au changement climatique, au moins dans les événements de cycle et d'inondation hydrologiques pour fournir une base solide pour atténuer les impacts du changement climatique et s'adapter à ces défis. Le but de cette étude est de présenter une méthodologie pour évaluer les impacts de différents scénarios de changement climatique sur une zone inondable du bassin de la rivière côtière dans la région centrale du Viet Nam - bassin versant de Vu Gia Thu Bon. Les simulations hydrologiques sont basées sur un modèle hydrologique déterministe validé qui intègre la géologie, les sols, la topographie, les systèmes fluviaux et les variables climatiques. Le climat de la journée présente, sur la période de 1991-2010 a été raisonnablement simulée par le modèle hydrologique. Climat futur (2091-2100) information a été obtenue à partir d'une réduction d'échelle dynamique des modèles climatiques mondiaux. L'étude analyse également les changements dans la dynamique des inondations de la région de l'étude, le changement hydrologique et les incertitudes du changement climatique simulation

熱帯山岳地域における主要道路沿いの地すべり災害リスクの統合的管理

東北学院大学平成29年

Detecting and Modeling the Changes of Land Use/Cover for Land Use Planning in Da Nang City, Viet Nam

The geometrical accuracy of georeferenced digital surfacemodels (DTM) obtained fromimages captured bymicro-UAVs and processed by using structure frommotion (SfM) photogrammetry depends on several factors, including flight design, camera quality, camera calibration, SfM algorithms and georeferencing strategy. This paper focusses on the critical role of the number and location of ground control points (GCP) used during the georeferencing stage. A challenging case study involving an area of 1200+ ha, 100+ GCP and 2500+ photos was used. Three thousand, four hundred and sixty-five different combinations of control points were introduced in the bundle adjustment, whilst the accuracy of the model was evaluated using both control points and independent check points. The analysis demonstrates how much the accuracy improves as the number of GCP points increases, as well as the importance of an even distribution, how much the accuracy is overestimated when it is quantified only using control points rather than independent check points, and how the ground sample distance (GSD) of a project relates to the maximum accuracy that can be achieved

Flood risk assessment of the Crocodile River, Mpumalanga

A dissertation submitted to the School of Geography, Archaeology and Environmental Studies, Faculty of Science at the University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science. Johannesburg, 2016.The Crocodile River East in Mpumalanga Province, South Africa, has seen three major floods in a twenty-four-month period, specifically January 2011, January 2012 and January 2013. The damage included the loss of life, damage and/or loss of public or private properties, agricultural land loss, and damage to biodiversity and river geomorphology. The purpose of this study was to understand the consequences and risks to livelihoods and river basin systems due to flooding of the river. The study focused on a segment of the Crocodile River East, between Riverside and Tekwane. The study used historic hydro-climatic data for the Crocodile River to determine the critical threshold for past flood events and to predict the extent of future flood events. Hydrological modelling coupled with the HEC-RAS hydraulic model enabled the simulation of these future flood events. The use of orthophotos and digital elevation models (DEMs) allowed for a spatial representation of the areas affected during the flood events. Flood hazard maps and flood risk maps were then developed for the identified flood events within a Geographical Information System (GIS). The maps enabled the identification of high risk and flood prone areas along this segment of the Crocodile River Basin. The results showed that when discharge reaches 241.75 m3/s, both locations (Riverside and Tekwane) are at risk to flooding. This is therefore the threshold for which the two locations are likely to be flooded. This study provides a methodology to determine the spatial extent of past and modelled future river flood events. As such, outcomes of this study may aid in the understanding of flood hazard extent and flood prone areas, and may thus help catchment management authorities and institutions in flood reconstruction and flood risk management. The employed methodology can aid effective spatial planning, and can also be extended at the basin scale through integration with the existent flood warning system to gain an estimate of flood extent and flood risk.TG201

Development of a Computerized Aid to Integrated Land Use Planning (CAILUP) at regional level in irrigated areas : a case study for the Qaun Lo Phung Hiep region in the Mekong Delta, Vietnam

The problem - Objectives of the studyLand use planning is an essential activity in any country, because the demands for different land uses usually exceed the available resources. Land use planning implies weighting of trade-offs among conflicting goals, as different interests exist in society. Demands for water often also exceed the available resources.The objectives of this study are to develop and implement a method and corresponding software system for integrated land use planning at regional level in irrigated areas, and to test the method and the system in the Quan Lo Phung Hiep region in the Mekong Delta, Vietnam. The System Development Methodology (SDM) comprising seven specific phases was applied in the study. A Computerized Aid to Integrated Land Use Planning, "CAILUP", was formulated.The research conceptThe greatest challenge in land use planning is how to incorporate the diversity in land use , comprising land users, goals, management and technologies, into the planning process. The CAILUP approach takes into account the diversity in land use by integrating promising land uses for agriculture, fisheries and forestry with land uses for other purposes.Integration is a major issue in land use planning. CAILUP focuses on integration of land use selections at different hierarchical levels, of bio-physical and socio-economic factors, of local expertise and global (international) expertise, and computer technology and land use planning.CAILUP takes into account integration among hierarchical levels by combining top-down and bottom-up approaches. Interventions are based on the goals of regional development in the context of the whole country. The feasibility of these interventions is judged by taking into account the preferences and priorities of the local land users, and subsequently all achievements and impacts from these interventions are evaluated. Decisions on land use can be considered as 'public decisions' with contributions from scientists, planners, decisionmakers, sectoral agencies and land users. Integration in 'public decision' is carried out by simulating the decision process.An IBS ( Integrated Bio-physical and Socio-economic ) approach is proposed to assess the effects of water management. Integration requires the equal resolution (in space and time) of data on both bio-physical and socio-economic factors. Land units are delineated by administrative boundaries and limits of key physical interventions.Land use planning can also be considered as a process of multi-sectoral integration . A key intervention is determined, i.e. construction of a water management system for an irrigated region. Other interventions are supplementary interventions to improve water management efficiency. A land use planning team needs to comprise a wide range of expertise . CAILUP comprises a knowledge base that integrates expert knowledge from both local (regional and national) and global expertise.Simulation modelling is a promising technique in land use planning to achieve integration. The strategy in modelling of CAILUP is to integrate simple sub-models of all relevant components, rather than only to include a few complex sub-models developed for single disciplinary research. CAELUP provides functions to analyse the impact of different hypotheses or scenarios formulated by planners. A scenario comprises a set of actions and effects in which goals are achieved to a certain degree. The impact of water management on the physical conditions is first evaluated. The new physical conditions lead to new biophysical production levels that are used to determine an integrated feasibility for each land use type by comparison with socio-economic criteria at farm level. This feasibility is used, in combination with Government policy objectives, to formulate a land use plan. Finally, achievements based on this plan and its impacts on bio-physical and socio-economic conditions are examined.Integration of computer technology and land use planning will be achieved by developing a system consisting of quantitative models, databases and GIS based on the concepts of decision support systems and expert systems.A Computerized Aid to Integrated Land Use PlanningCAILUP consists of four units : a core expert unit, a database unit, a GIS unit and a model unit. The model unit, a major component to realize the system function, comprises a mathematical model developed on the basis of a conceptual model.The conceptual model is developed in a sequence of identifying issues, goals and indicators, relevant land use types, relevant components, factors, spatial extent and spatial resolution, time horizon and time steps, and "without" and "with" intervention cases.The mathematical model comprises 14 sub-models:[1] Intervention Generating Sub-model to generate a data set for the "without" or "with"intervention cases.[2] Physical Impact Sub-model to generate a data set of modified physical conditions.[3] Bio-physical Sub-model (Agriculture, Fisheries, Forestry) to estimate yields and the selected crop calendars under modified physical conditions.[4] Economic Sub-model at Farm Level to generate the combined bio-physical/economic feasibility based on financial criteria defined at farm level.[5] Social Sub-model at Farm Level to integrate social preferences with biophysical/economic feasibility to generate integrated feasibility.[6] Demography Sub-model to generate data on population and labour force.[7] Land Use Weighting Sub-model to determine weighting factors based on the integrated feasibility and Government policy.[8] Land Use Allocation Sub-model to generate land resource use on the basis of the weighting factor and rules in land use conversion.[9] Production Sub-model to generate total production by multiplying area with yield.[10] Supplementary Intervention Sub-model to generate supplementary interventions required to support the land use scenario.[11] Economic Sub-model at Regional Level to calculate the economic returns at land unit and regional levels.[12] Social Sub-model at Regional Level to calculate the socio-economic indicators at land unit and regional levels.[13] Environmental Impact Sub-model to calculate indicators expressing environmental impacts.[14] Goal and Impact Analysis Sub-model to generate a ranking value for the selected scenario.An example in the real worldThe Quan Lo Phung Hiep region , with a total area of approximately 450,000 hectares and located in the Mekong Delta, Vietnam, was selected for the case study. Agricultural production in this region is constrained by adverse soil and water conditions. Low rainfall during the dry season prevents agricultural production without irrigation. However, salt water intrusion from the sea makes water quality in most parts of the region unsuitable for irrigation. In the early part of the rainy season, leachates from the acid sulphate soil area contaminate surface water and reduce its pH to values below 4, which is detrimental to agricultural and aquacultural production.In the region, 85% of the population is engaged in agricultural, fisheries and forestry activities. The relevant land use types are single crops (rice, sugarcane, etc.) or a combination of various crops/activities (double rice, rice+beans, rice+shrimp, etc.) under different management techniques. Rice is the most important crop. Living standards are reportedly lower in areas of salt and brackish water than in areas of fresh water.Water management to prevent salt water intrusion and to increase the supply of fresh water from the Mekong river is considered a key intervention for development of the region. Main objectives of water management are to increase total food production and income and to improve living conditions. A medium scale protection option, i.e. protection and irrigation of the central part by 11 medium-size sluices, was selected. Seven schedules of water management construction were formulated, depending on the availability of funds and the strategy in minimizing the acid water effects.Four land use strategies were formulated: Maximize rice production, Maximize income from rice production, Crop diversification and Minimize effects of acid water.CAILUP for the Quan Lo Phung Hiep region has been developed and used in analysing the effects of different construction schedules and land use strategies.Data used for calibration are data on water conditions in 1989-1990, data on yields from 1986 to 1990, data on population and land use areas in 1985 and 1990, and data on production from 1985 to 1990. Calibration of single sub-models was followed by calibration of series of submodels. The model then was validated with inventory data from 1991 to 1994.Twenty eight development scenarios combining 7 construction schedules of the water management system with 4 land use strategies, were compared with a "without case" in which the new water management system was assumed absent. Single goal scores and total score were used as main outputs for evaluation of development scenarios. Sensitivity analysis has been carried out to provide a measure of the sensitivity of the outputs to either parameters, functions or sub-models, and to analyse the impact of changes in values of inputs on scenario scores.A construction schedule was selected on the basis of development objectives and possible impacts reflected by scenario scores, taking into account the institutional situation in the region. Selection of a land use strategy is more difficult because each land use strategy has the highest score for at least one of the goals in the situations considered. A rice-oriented strategy has been selected, with more crop diversification outside of the protected area.Conclusions and recommendationsThe objectives of the study have been attained. Taking into account major issues in land use planning methodology, CAILUP was developed to facilitate integration in land use planning. A corresponding software system was developed and tested successfully for the Quan Lo Phung Hiep region. To be developed and applied successfully, CAILUP requires suitable conditions in terms of human resources, data and information, and hardware and software packages.Although the above conditions have been adopted, development and applications of CAILUP are still confronted with many challenges each deriving from the existence of two alternatives (see Chapter V: Section 2). A cycle exists in which one challenge becomes dominant and is the main subject of many studies during a number of years, and there is also a cyclic behaviour of the two alternatives of each challenge. The attempt in further studies is to develop and apply the CAILUP system adapted to these cycles