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Decision Support for Flood Risk Management at the Yangtze River by GIS/RS-Based Flood Damage Estimation.

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Decision Support for Flood Risk Management at the Yangtze River by GIS/RS-Based Flood Damage Estimation.

... As can be seen above, four of the six heaviest flooding disasters during the second half of the 20 th century occurred in the 1990s. Several studies dealing with analyses of precipitation data from the Yangtze River basin for this period point towards a concentration of summer precipitation within a shorter period of time (Becker et al. 2003(Becker et al. , 2006gemmer 2004). In addition to a significantly decreasing evaporation in that region caused by decreasing wind speed as well as decreasing radiation (Wang et al. 2007), this has led to an aggravation of the flood risk since the 1990s. ...
... Especially the Yangtze River's middle and lower reaches are extremely susceptible to floods, which among other reasons is due to the flat relief. However, damages caused by floods are not limited to these regions, but have also been reported from the Sichuan basin, a plane region in the Yangtze River's upper reaches (gemmer 2000;Hartmann 2002). During the second half of the 20 th century, the 1981-flood caused the most damages here. ...
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In the last ten years, the application of neural network models has become an emerging field of research in the field of hydrology In the present study, three different neural network models, namely the Multilayer Perceptron (MLP), the Jordan net, and the Elman net were used for forecasting water levels at Cuntan station, located at the Yangtze River's upper reaches. The performances of the neural network models were compared with each other and with the results of a multiple linear regression (MLR) model. As input variables for the models, not only were precipitation data and antecedent water levels implemented, but also two climatic variables which are usually left out in the field of neural network modeling: evaporation and snow data. Before the models were adopted, the optimal lead time between the input variables and the model output was determined by means of a cross-correlation analysis. The highly significant correlation between the model input and output already indicated a highly linear relationship. Accordingly, the MLR model showed the best performance, even though the results of the other models are only slightly worse. The good capability of the Jordan net in forecasting high water levels should be investigated further. In predicting water levels in general, the integrated snow data improved the performance of the different models only marginally. However, the integration of evaporation data definitely improved the modeling results.
... According to field investigation of flood hazard information in the basin, the parameters of the model were determined, making the simulated results of each hidden point closer to the inspection results. Using the simulated flood course of the river basin section to determine the critical rainfall at different depths of submerged water, disaster risk assessment of flood-affected areas is carried out based on submerged maps[18] [19]. Due to the remote terrain and lack of hydrological data, most of the methods are of wide applicability. ...
... Researches pertaining to flood risk assessment using GIS technology have been done by various researchers, for instance by King and Xu (1997), Wang et al. (1999), King and Gemmer (2001), King et al. (2001), andGemmer (2004). In (2006), give an idea for the development of the methodology. ...
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Sea level rise (SLR) as a result of global warming has an impact on the increasing inundation on the coastal area. Nowadays, Semarang coastal area in Indonesia is already subject to coastal hazard due to tidal inundation and land subsidence. The impact of the inundation is predicted to be even more severe with the scenario of sea level rise. This paper concentrates on the risk assessment to the population, land use, and monetary losses as a result of coastal inundation under enhanced sea level rise. This paper uses the scenario of the depth of inundation to generate coastal inundation model using GIS-Technology. Anticipatory issues including methodology development for hazard assessment would be necessary for Semarang coastal area, and therefore, geo-information technology can be considered as a useful tool to rapidly assess the impact of the coastal hazard and evaluate the economic losses.
Chapter
Introduction Observed changes of precipitation and temperature Observed changes of streamflow and flood/drought indices Projections Mitigating the negative effects of climatic change References
Article
This study aims to investigate whether, to what extent and how a transition toward integrated flood management has taken place in the Dongting Lake area at the middle Yangtze. Accordingly, we conducted a longitudinal research of its flood management (1949–2009). We developed an analytical framework linking regime components to two societal learning types (double and triple-loop learning) that are key to a regime transition. Our study shows that the transition toward integrated flood management has already started, but the whole regime transformation will still take time to complete, due to, for example, the not-yet-ready decision-making processes that shape the structure changes as well as the incompatibilities between what is on paper and real implementation. To understand how the regime transition took place, we investigated where and how triple-loop learning was initiated as well as how so-called “informal learning processes” has contributed to the transition of Dongting flood management.
Article
In flood modelling, the characteristics of the upstream flood hydrographs may have a large influence on simulation results. Hence, the focus of this paper is to investigate the influence of shape and magnitude of hydrographs on detention basins; especially on suspended sediment and micro-pollutant transport and on dynamics of nutrients, oxygen and organic carbon. Five flood events with different filling and emptying curves were created by normalising the flood hydrographs and performing a cluster analysis. The resulting clusters describe typical, realistic hydrographs, whose discharges were used as boundary conditions for the simulations. The models DYNHYD, TOXI and EUTRO from the WASP5 modelling package were used as a basis for the simulations. Monte-Carlo simulations were carried out to investigate the differences and analogies in sediment deposition, depletion of oxygen or growth of phytoplankton for each cluster. The results show that the shape of the upstream hydrograph and the severity of the flood do not have a significant influence on the amount of deposited sediment and particulate zinc. However, the hydrograph characteristics have an impact on the severity of oxygen depletion and phytoplankton growth, which is a consequence of the control strategy of flood water diversion by the opening and closing times of the flood gates and the retention times of flood water in the detention basins.
Article
The present study examines the spatial and temporal trends of precipitation, flood/drought, runoff, high and low river flow during flood season (May–October) for the Yangtze River Basin. Analyses are based on daily meteorological data for 137 stations from 1960 to 2004, daily hydrological data for two discharge-measuring stations at the Yangtze River and monthly hydrological data for one station for the same reference period. Flood/drought examination was done for the western, middle, and lower Yangtze River Basin. Significant precipitation changes can be detected for June and July during 1960–2004. The strongest precipitation increase was detected in the lower Yangtze region. A statistically significant negative trend can be found in September over the Yangtze River Basin, especially at the middle region. Changes of the precipitation extremes from May to October are of direct importance to the occurrences of high and low river flow. The main increase of flooding events can be detected for July in the lower Yangtze region, together with significant upward trends both for the monthly runoff and for the high river water stage. Drought frequency increased in the middle Yangtze River Basin in May, September and October, where downward trends for the monthly runoff and low river flow especially in May. During these months, flood and drought hazards in the Yangtze River Basin have been aggravated.
Chapter
In this contribution it is argued that the current challenge in flood damage research consists in developing a better understanding of the interrelations and social dynamics of flood risk perception, preparedness, vulnerability, flood damage and flood management, and to take this into account in a modern design of flood damage analysis and flood risk management. Accordingly, the sections of this contribution are organised as follows: In the next section the relationship between flood damage, vulnerability and risk perception is analysed and clarified. Section three deals with state-of-the-art approaches to flood damage analysis. The fourth section discusses the shortcomings of the current approaches with a special focus on the disregard for socio-economic factors and methods. Finally, the contribution concludes with an outlook, presenting current EU research efforts to improve state-of-the-art approaches to flood damage analysis.
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Precipitation trends in the Yangtze River catchment (PR China) have been analyzed for the past 50years by applying the Mann-Kendall trend test and geospatial analyses. Monthly precipitation trends of 36 stations have been calculated. Significant positive trends at many stations can be observed for the summer months, which naturally show precipitation maxima. They were preceded and/or followed by negative trends. This observation points towards a concentration of summer precipitation within a shorter period of time. The analysis of a second data set on a gridded basis with 0.5° resolution reveals trends with distinct spatial patterns. The combination of classic trend tests and spatially interpolated precipitation data sets allows the spatiotemporal visualization of detected trends. Months with positive trends emphasize the aggravation of severe situation in a region, which is particularly prone to flood disasters during summer. Reasons for the observed trends were found in variations in the meridional wind pattern at the 850hPa level, which account for an increased transport of warm moist air to the Yangtze River catchment during the summer months.
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