In recent years, flash flood disasters have occurred frequently in southwest China due to the increased frequency of extreme climate events. To solve this problem, great efforts have been made in studying the process ...In recent years, flash flood disasters have occurred frequently in southwest China due to the increased frequency of extreme climate events. To solve this problem, great efforts have been made in studying the process of flash flood. However, little attention was paid on bearing body of hazard, the clusters of buildings. Thus the real disaster mechanism of flash flood remains unclear.Accordingly, based on the experiments of artificial flash floods in a conceptual solid model, this paper focuses on the flood-impacted inundation characteristics of the building clusters at different locations of the gully model, in order to obtain a better understanding of the disaster process and the interaction between the flash floods and building clusters. The results showed that, in a typical smallscale flash flood gully with hot and dry climate, 1)clusters of buildings on an alluvial fan could reduce about 35% of the flooding area by blocking the diffusion of the flood to the depression areas, and could also promote the deposition in lower reaches of the river channel by blocking the overbank flow from going back into the channel, making the width-depth ratio of the channel larger. 2) The flash flood rates of disaster and hazard on the alluvial fan are generally higher than that of the inner gully. For the inner gully,buildings located on the beaches along the lower river and the transitional areas of the straight channel and channel bends can easily be affected because of their lower elevations. For the alluvial fan, buildings nearby the meanders suffer the greatest impacts because of bank collapsing and flooding. 3) The safe vertical distance from a building to the river channel is 13 m for the buildings in the inner gully under extreme floods. Below this threshold, the smaller the vertical distance is, the greater the risk exposure is. For the buildings on the alluvial fan, especially for the buildings near the concave bank of the top rush point,the horizontal distance is more important, and the safe value is 80 m under extreme floods.展开更多
Mountain catchments are prone to flash flooding due to heavy rainfall. Enhanced understanding of the generation and evolution processes of flash floods is essential for effective flood risk management. However, tradit...Mountain catchments are prone to flash flooding due to heavy rainfall. Enhanced understanding of the generation and evolution processes of flash floods is essential for effective flood risk management. However, traditional distributed hydrological models based on kinematic and diffusion wave approximations ignore certain physical mechanisms of flash floods and thus bear excessive uncertainty. Here a hydrodynamic model is presented for flash floods based on the full two-dimensional shallow water equations incorporating rainfall and infiltration. Laboratory experiments of overland flows were modelled to illustrate the capability of the model. Then the model was applied to resolve two observed flash floods of distinct magnitudes in the Lengkou catchment in Shanxi Province, China. The present model is shown to be able to reproduce the flood flows fairly well compared to the observed data. The spatial distribution of rainfall is shown to be crucial for the modelling of flash floods. Sensitivity analyses of the model parameters reveal that the stage and discharge hydrographs are more sensitive to the Manning roughness and initial water content in the catchment than to the Green-Ampt head. Most notably, as the flash flood augments due to heavier rainfall, the modelling results agree with observed data better, which clearly characterizes the paramount role of rainfall in dictating the floods. From practical perspectives, the proposed model is more appropriate for modelling large flash floods.展开更多
In this paper,the northern mountainous area of Fuzhou City which is an ungauged basin has been taken for example to discuss the method of design flood calculation by means of combining the DEM(digital elevation model)...In this paper,the northern mountainous area of Fuzhou City which is an ungauged basin has been taken for example to discuss the method of design flood calculation by means of combining the DEM(digital elevation model) and the Xin'anjiang Model(three components).The problem of estimating the parameters of the runoff model has been solved by using the parameters of the reference station.In the conflux calculation,the isochrones are obtained by DEM which helps to avoid the cumbersome work of drawing them on the map.With the establishment of the digital elevation model throughout the country,it is practically significant to use it in the hydrological estimation.展开更多
Critical rainfall estimation for early warning of rainstorm-induced flash flood is an inverse rainstorm-runoff process based on warning discharge threshold for a warning station of interest in a watershed. The key asp...Critical rainfall estimation for early warning of rainstorm-induced flash flood is an inverse rainstorm-runoff process based on warning discharge threshold for a warning station of interest in a watershed. The key aspects of critical rainfall include rainfall amount and rainfall duration. Storm pattern affects highly the estimation of critical rainfall. Using hydrological modeling technique with detailed sub-basin delineation and manual for design rainstorm-runoff computation, this study first introduced basic concept and analysis methods on critical rainfall for flash flood early warning, then, investigated the responses of flash flood warning critical rainfall to storm pattern. Taking south branch of Censhui watershed in China as an example, critical rainfall in case of typical storm patterns for early warning of rainstorm-induced flash flood were estimated at 3 warning stations. This research illustrates that storm pattern plays important role in the estimation of critical rainfall and enough attention should also be paid to storm pattern when making a decision on whether a warning to be issued or not.展开更多
Flash floods are a natural disaster that occurs annually, especially in the mountainous terrain and steep slopes of northern Thailand. The current flood forecasting systems and tools are available but have low accurac...Flash floods are a natural disaster that occurs annually, especially in the mountainous terrain and steep slopes of northern Thailand. The current flood forecasting systems and tools are available but have low accuracy and efficiency. The numbers of rainfall and runoff stations are less, because the access to the station area is difficult. Additionally, the operation and maintenance costs are high. Hydrological modeling of a SWAT （Soil and Water Assessment Tool） was used in this study with the application of three days weather forecast from the NWP （numerical weather prediction）, which provided temperature, relative humidity, rainfall, sunshine and wind speed. The data from NWP and SWAT were used to simulate the runoff from the Nan River in the last 10 years （2000-2010）. It was found that the simulated flow rate for the main streams using data from NWP were higher than the observations. At the N64 and Nl stations, the ratios of the maximum simulated flow rate to the observations were equal to 108% and 118%, respectively. However, for the tributaries, it was found that the simulated flow rate using NWP data was lower than the observations, but, it was still within the acceptable range of not greater than 20%,6. At N65, D090201 and D090203 stations, the ratio of the maximum simulated flow rate were 90.0%, 83.0% and 86.0%, respectively. This was due to the rainfall from the NWP model being greater than the measured rainfall. The NWP rainfall was distributed all over the area while the rainfall data from the measurements were obtained from specific points. Therefore, the rain from the NWP model is very useful especially for the watershed areas without rain gauge stations. In summary, the data from the NWP can be used with the SWAT model and provides relatively sound results despite the value for the main river being slightly higher than the observed data. Consequently, the output can be used to create a flood map for flash flood warning in the area.展开更多
Climate induced disasters such as cloudburst triggered flash floods, debris-flow, mass movements and landslides are very common phenomenon in the Himalaya. There are many instances in the recent past when these catast...Climate induced disasters such as cloudburst triggered flash floods, debris-flow, mass movements and landslides are very common phenomenon in the Himalaya. There are many instances in the recent past when these catastrophes caused heavy losses to lives and tremendous damage to property. One of the important characteristics of the Himalaya during the monsoon season is heavy downpour （cloudburst） which is due to extreme weather condition. Further, the landscape is very fragile and the human settlements are located either along the perennial streams of big rivers or on the unstable slopes. These perennial streams and big rivers are highly violent during the monsoon and whenever, the water level of these streams rises, it causes heavy loss to property and lives through destruction of the human settlements located along these courses. During the recent past, extreme changes in the climatic conditions have been seen largely due to the anthropogenic activities, i.e., population growth and large-scale deforestation. It has not only affected the climatic conditions but also affected the daily life of the inhabitants. This article examines the extreme weather related disasters in the Himalaya and gives a description of two deadly cloudburst triggered flashfloods that occurred in the Kedarnath and Badrinath valleys, which left the entire landscape devastated. This was followed by devastation of the settlements, agricultural fields, and thousands of lives were wiped out during this catastrophe. Rainfall data were collected to know about the changes in the climatic conditions and their impacts on the disaster in this part of the Himalaya.展开更多
Severe solar events manifested by highly energetic X-Ray events accompanied by coronal mass ejections and proton flares caused flash floods in Makkah AI-Mukaramab, A1-Madinah AI-Munawarah and Jeddah. The responses can...Severe solar events manifested by highly energetic X-Ray events accompanied by coronal mass ejections and proton flares caused flash floods in Makkah AI-Mukaramab, A1-Madinah AI-Munawarah and Jeddah. The responses can be prompt, delayed or prompt-delayed, suggesting that the protons entered the troposphere either through the opening of a direct gate in the magnetosphere to the location concer.led due to magnetic reconnection, through the polar gates or through those two paths respectively. The authors suggest that there is a magnetic anomaly in Makkah AI-Mukaramah area which makes it liable to be subjected to flash floods. The width of the solar streams determines the width of the gate opened in the magnetosphere via magnetic reconnection and thus narrow streams affect only one location of the three cities while extended width streams can cause flash floods in all of Makkah AI-Mukaramah AI-Madinah AI Munawarah and Jeddah. In addition, the November 24-26 Jeddah flash flood could be attributed to a prompt event due to a moderately fast solar stream that arrived the earth on those days.展开更多
Geohazards appear to be increasing in frequency globally. It is of necessity to actively manage these natural hazards to minimize loss of life and property. From an early warning perspective, this paper stresses the p...Geohazards appear to be increasing in frequency globally. It is of necessity to actively manage these natural hazards to minimize loss of life and property. From an early warning perspective, this paper stresses the potential fatal flood hazard represented by the huge volume of water in Tianchi Lake, the unique geography of Changbai Mountain, and the limited flood control ability in the upstream of the Songhua River. Northeast Asian countries should keep a watchful eye on the Changbai volcano cooperatively, and Chinese government especially needs to prepare plans for fighting a flood in advance.展开更多
Dam-break analysis is of great importance in mountain environment,especially where reservoirs are located upstream of densely populated areas and hydraulic hazard should be assessed for land planning purposes.Accordin...Dam-break analysis is of great importance in mountain environment,especially where reservoirs are located upstream of densely populated areas and hydraulic hazard should be assessed for land planning purposes.Accordingly,there is a need to identify suitable operative tools which may differ from the ones used in flat flood-prone areas.This paper shows the results provided by a 1D and a 2D model based on the Shallow Water Equations(SWE) for dam-break wave propagation in alpine regions.The 1D model takes advantage of a topographic toolkit that includes an algorithm for pre-processing the Digital Elevation Model(DEM) and of a novel criterion for the automatic cross-section space refinement.The 2D model is FLO-2D,a commercial software widely used for flood routing in mountain areas.In order to verify the predictive effectiveness of these numerical models,the test case of the Cancano dam-break has been recovered from the historical study of De Marchi(1945),which provides a unique laboratory data set concerning the consequences of the potential collapse of the former Cancano dam(Northern Italy).The measured discharge hydrograph at the dam also provides the data to test a simplified method recently proposed for the characterization of the hydrograph following a sudden dam-break.展开更多
Fifty cases of regional yearly extreme precipitation events （RYEPEs） were identified over the Yangtze-Huaihe River Valley （YHRV） during 1979-2016 applying the statistical percentile method. There were five types o...Fifty cases of regional yearly extreme precipitation events （RYEPEs） were identified over the Yangtze-Huaihe River Valley （YHRV） during 1979-2016 applying the statistical percentile method. There were five types of RYEPEs, namely Yangtze Meiyu （YM-RYEPE）, Huaihe Meiyu （HM-RYEPE）, southwest-northeast-oriented Meiyu （SWNE-RYEPE） and typhoon I and II （TC-RYEPE） types of RYEPEs. Potential vorticity diagnosis showed that propagation trajectories of the RYEPEs along the Western Pacific Subtropical High and its steering flow were concentrated over the southern YHRV. As a result, the strongest and most frequently RYEPEs events, about 16-21 cases with average rainfall above 100 mm, occurred in the southern YHRV, particularly in the Nanjing metropolitan area. There have been 14 cases of flood-inducing RYEPEs since 1979, with the submerged area exceeding 120 km2 as simulated by the FloodArea hydraulic model, comprising six HM-RYEPEs, five YM- RYEPEs, two TC-RYEPEs, and one SWNE-RYEPE. The combination of evolving RYEPEs and rapid expansion of urban agglomeration is most likely to change the flood risk distribution over the Nanjing metropolitan area in the future. In the RCP6.0 （RCPS.5） scenario, the built-up area increases at a rate of about 10.41 km2 （10 yr）-t（24.67 km2 （10 yr）-1） from 2010 to 2100, and the area of high flood risk correspondingly increases from 3.86 km2（3.86 km2） to 9.00 kin2（13.51 km2）. Areas of high flood risk are mainly located at Chishan Lake in Jurong, Lukou International Airport in Nanjing, Dongshan in Jiangning District, Lishui District and other low-lying areas. The accurate simulation of flood scenarios can help reduce losses due to torrential flooding and improve early warnings, evacuation planning and risk analysis. More attention should be paid to the projected high flood risk because of the concentrated population, industrial zones and social wealth throughout the Nanjing metropolitan area.展开更多
基金supported by the Specific Research of China Institute of Water Resources and Hydropower Research (Grant Nos. Fangji 1240)Chinese Ministry of Water Resources (Grant Nos. 201301058 and 20131059)the Basic Research Fund for Central Public Research Institutes (Grant No. CKSF2015010/TB)
文摘In recent years, flash flood disasters have occurred frequently in southwest China due to the increased frequency of extreme climate events. To solve this problem, great efforts have been made in studying the process of flash flood. However, little attention was paid on bearing body of hazard, the clusters of buildings. Thus the real disaster mechanism of flash flood remains unclear.Accordingly, based on the experiments of artificial flash floods in a conceptual solid model, this paper focuses on the flood-impacted inundation characteristics of the building clusters at different locations of the gully model, in order to obtain a better understanding of the disaster process and the interaction between the flash floods and building clusters. The results showed that, in a typical smallscale flash flood gully with hot and dry climate, 1)clusters of buildings on an alluvial fan could reduce about 35% of the flooding area by blocking the diffusion of the flood to the depression areas, and could also promote the deposition in lower reaches of the river channel by blocking the overbank flow from going back into the channel, making the width-depth ratio of the channel larger. 2) The flash flood rates of disaster and hazard on the alluvial fan are generally higher than that of the inner gully. For the inner gully,buildings located on the beaches along the lower river and the transitional areas of the straight channel and channel bends can easily be affected because of their lower elevations. For the alluvial fan, buildings nearby the meanders suffer the greatest impacts because of bank collapsing and flooding. 3) The safe vertical distance from a building to the river channel is 13 m for the buildings in the inner gully under extreme floods. Below this threshold, the smaller the vertical distance is, the greater the risk exposure is. For the buildings on the alluvial fan, especially for the buildings near the concave bank of the top rush point,the horizontal distance is more important, and the safe value is 80 m under extreme floods.
基金funded by Natural Science Foundation of China (Grants Nos. 51279144 and 11432015)Chinese Academy of Sciences (Grant No. KZZD-EW-05-01-03)
文摘Mountain catchments are prone to flash flooding due to heavy rainfall. Enhanced understanding of the generation and evolution processes of flash floods is essential for effective flood risk management. However, traditional distributed hydrological models based on kinematic and diffusion wave approximations ignore certain physical mechanisms of flash floods and thus bear excessive uncertainty. Here a hydrodynamic model is presented for flash floods based on the full two-dimensional shallow water equations incorporating rainfall and infiltration. Laboratory experiments of overland flows were modelled to illustrate the capability of the model. Then the model was applied to resolve two observed flash floods of distinct magnitudes in the Lengkou catchment in Shanxi Province, China. The present model is shown to be able to reproduce the flood flows fairly well compared to the observed data. The spatial distribution of rainfall is shown to be crucial for the modelling of flash floods. Sensitivity analyses of the model parameters reveal that the stage and discharge hydrographs are more sensitive to the Manning roughness and initial water content in the catchment than to the Green-Ampt head. Most notably, as the flash flood augments due to heavier rainfall, the modelling results agree with observed data better, which clearly characterizes the paramount role of rainfall in dictating the floods. From practical perspectives, the proposed model is more appropriate for modelling large flash floods.
基金National Science Foundation of China (No. 50879051)
文摘In this paper,the northern mountainous area of Fuzhou City which is an ungauged basin has been taken for example to discuss the method of design flood calculation by means of combining the DEM(digital elevation model) and the Xin'anjiang Model(three components).The problem of estimating the parameters of the runoff model has been solved by using the parameters of the reference station.In the conflux calculation,the isochrones are obtained by DEM which helps to avoid the cumbersome work of drawing them on the map.With the establishment of the digital elevation model throughout the country,it is practically significant to use it in the hydrological estimation.
文摘Critical rainfall estimation for early warning of rainstorm-induced flash flood is an inverse rainstorm-runoff process based on warning discharge threshold for a warning station of interest in a watershed. The key aspects of critical rainfall include rainfall amount and rainfall duration. Storm pattern affects highly the estimation of critical rainfall. Using hydrological modeling technique with detailed sub-basin delineation and manual for design rainstorm-runoff computation, this study first introduced basic concept and analysis methods on critical rainfall for flash flood early warning, then, investigated the responses of flash flood warning critical rainfall to storm pattern. Taking south branch of Censhui watershed in China as an example, critical rainfall in case of typical storm patterns for early warning of rainstorm-induced flash flood were estimated at 3 warning stations. This research illustrates that storm pattern plays important role in the estimation of critical rainfall and enough attention should also be paid to storm pattern when making a decision on whether a warning to be issued or not.
文摘Flash floods are a natural disaster that occurs annually, especially in the mountainous terrain and steep slopes of northern Thailand. The current flood forecasting systems and tools are available but have low accuracy and efficiency. The numbers of rainfall and runoff stations are less, because the access to the station area is difficult. Additionally, the operation and maintenance costs are high. Hydrological modeling of a SWAT （Soil and Water Assessment Tool） was used in this study with the application of three days weather forecast from the NWP （numerical weather prediction）, which provided temperature, relative humidity, rainfall, sunshine and wind speed. The data from NWP and SWAT were used to simulate the runoff from the Nan River in the last 10 years （2000-2010）. It was found that the simulated flow rate for the main streams using data from NWP were higher than the observations. At the N64 and Nl stations, the ratios of the maximum simulated flow rate to the observations were equal to 108% and 118%, respectively. However, for the tributaries, it was found that the simulated flow rate using NWP data was lower than the observations, but, it was still within the acceptable range of not greater than 20%,6. At N65, D090201 and D090203 stations, the ratio of the maximum simulated flow rate were 90.0%, 83.0% and 86.0%, respectively. This was due to the rainfall from the NWP model being greater than the measured rainfall. The NWP rainfall was distributed all over the area while the rainfall data from the measurements were obtained from specific points. Therefore, the rain from the NWP model is very useful especially for the watershed areas without rain gauge stations. In summary, the data from the NWP can be used with the SWAT model and provides relatively sound results despite the value for the main river being slightly higher than the observed data. Consequently, the output can be used to create a flood map for flash flood warning in the area.
文摘Climate induced disasters such as cloudburst triggered flash floods, debris-flow, mass movements and landslides are very common phenomenon in the Himalaya. There are many instances in the recent past when these catastrophes caused heavy losses to lives and tremendous damage to property. One of the important characteristics of the Himalaya during the monsoon season is heavy downpour （cloudburst） which is due to extreme weather condition. Further, the landscape is very fragile and the human settlements are located either along the perennial streams of big rivers or on the unstable slopes. These perennial streams and big rivers are highly violent during the monsoon and whenever, the water level of these streams rises, it causes heavy loss to property and lives through destruction of the human settlements located along these courses. During the recent past, extreme changes in the climatic conditions have been seen largely due to the anthropogenic activities, i.e., population growth and large-scale deforestation. It has not only affected the climatic conditions but also affected the daily life of the inhabitants. This article examines the extreme weather related disasters in the Himalaya and gives a description of two deadly cloudburst triggered flashfloods that occurred in the Kedarnath and Badrinath valleys, which left the entire landscape devastated. This was followed by devastation of the settlements, agricultural fields, and thousands of lives were wiped out during this catastrophe. Rainfall data were collected to know about the changes in the climatic conditions and their impacts on the disaster in this part of the Himalaya.
文摘Severe solar events manifested by highly energetic X-Ray events accompanied by coronal mass ejections and proton flares caused flash floods in Makkah AI-Mukaramab, A1-Madinah AI-Munawarah and Jeddah. The responses can be prompt, delayed or prompt-delayed, suggesting that the protons entered the troposphere either through the opening of a direct gate in the magnetosphere to the location concer.led due to magnetic reconnection, through the polar gates or through those two paths respectively. The authors suggest that there is a magnetic anomaly in Makkah AI-Mukaramah area which makes it liable to be subjected to flash floods. The width of the solar streams determines the width of the gate opened in the magnetosphere via magnetic reconnection and thus narrow streams affect only one location of the three cities while extended width streams can cause flash floods in all of Makkah AI-Mukaramah AI-Madinah AI Munawarah and Jeddah. In addition, the November 24-26 Jeddah flash flood could be attributed to a prompt event due to a moderately fast solar stream that arrived the earth on those days.
基金the Knowledge Innovation Program of Chinese Academy of Sciences (Grant No. KZCX2-EW-319)the National Basic Research Program of China (Grant No. 2010CB951301)the National Natural Science Foundation of China (Grant No. 40871089)
文摘Geohazards appear to be increasing in frequency globally. It is of necessity to actively manage these natural hazards to minimize loss of life and property. From an early warning perspective, this paper stresses the potential fatal flood hazard represented by the huge volume of water in Tianchi Lake, the unique geography of Changbai Mountain, and the limited flood control ability in the upstream of the Songhua River. Northeast Asian countries should keep a watchful eye on the Changbai volcano cooperatively, and Chinese government especially needs to prepare plans for fighting a flood in advance.
基金developed within the European Project Kulturisk (Grant agreement 265280)
文摘Dam-break analysis is of great importance in mountain environment,especially where reservoirs are located upstream of densely populated areas and hydraulic hazard should be assessed for land planning purposes.Accordingly,there is a need to identify suitable operative tools which may differ from the ones used in flat flood-prone areas.This paper shows the results provided by a 1D and a 2D model based on the Shallow Water Equations(SWE) for dam-break wave propagation in alpine regions.The 1D model takes advantage of a topographic toolkit that includes an algorithm for pre-processing the Digital Elevation Model(DEM) and of a novel criterion for the automatic cross-section space refinement.The 2D model is FLO-2D,a commercial software widely used for flood routing in mountain areas.In order to verify the predictive effectiveness of these numerical models,the test case of the Cancano dam-break has been recovered from the historical study of De Marchi(1945),which provides a unique laboratory data set concerning the consequences of the potential collapse of the former Cancano dam(Northern Italy).The measured discharge hydrograph at the dam also provides the data to test a simplified method recently proposed for the characterization of the hydrograph following a sudden dam-break.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41205063 & 41330529)the China Meteorological Administration Special Public Welfare Research Fund (Grant No. GYHY201506006)+1 种基金the Project of Development of Key Techniques in Meteorological Forecasting Operation (Grant No. CMAHX20160404)the Huaihe Basin Meteorological Research Foundation (Grant No. HRM201605)
文摘Fifty cases of regional yearly extreme precipitation events （RYEPEs） were identified over the Yangtze-Huaihe River Valley （YHRV） during 1979-2016 applying the statistical percentile method. There were five types of RYEPEs, namely Yangtze Meiyu （YM-RYEPE）, Huaihe Meiyu （HM-RYEPE）, southwest-northeast-oriented Meiyu （SWNE-RYEPE） and typhoon I and II （TC-RYEPE） types of RYEPEs. Potential vorticity diagnosis showed that propagation trajectories of the RYEPEs along the Western Pacific Subtropical High and its steering flow were concentrated over the southern YHRV. As a result, the strongest and most frequently RYEPEs events, about 16-21 cases with average rainfall above 100 mm, occurred in the southern YHRV, particularly in the Nanjing metropolitan area. There have been 14 cases of flood-inducing RYEPEs since 1979, with the submerged area exceeding 120 km2 as simulated by the FloodArea hydraulic model, comprising six HM-RYEPEs, five YM- RYEPEs, two TC-RYEPEs, and one SWNE-RYEPE. The combination of evolving RYEPEs and rapid expansion of urban agglomeration is most likely to change the flood risk distribution over the Nanjing metropolitan area in the future. In the RCP6.0 （RCPS.5） scenario, the built-up area increases at a rate of about 10.41 km2 （10 yr）-t（24.67 km2 （10 yr）-1） from 2010 to 2100, and the area of high flood risk correspondingly increases from 3.86 km2（3.86 km2） to 9.00 kin2（13.51 km2）. Areas of high flood risk are mainly located at Chishan Lake in Jurong, Lukou International Airport in Nanjing, Dongshan in Jiangning District, Lishui District and other low-lying areas. The accurate simulation of flood scenarios can help reduce losses due to torrential flooding and improve early warnings, evacuation planning and risk analysis. More attention should be paid to the projected high flood risk because of the concentrated population, industrial zones and social wealth throughout the Nanjing metropolitan area.
