This article argues that the "sand flat-private field" pattern was the outcome of interaction between local society and national power in the course of exploitation of the Pearl River Delta. People used vari...This article argues that the "sand flat-private field" pattern was the outcome of interaction between local society and national power in the course of exploitation of the Pearl River Delta. People used various orthodox cultural symbols to maintain their own economic power and political influence. Thus, this arrangement of geographical space was in reality a local power structure in a context of national identity.展开更多
In traditional urban geography, city contact research is a classic study element in city research. In general, researchers use the traditional gravity model to characterize the contacts that exist between two cities. ...In traditional urban geography, city contact research is a classic study element in city research. In general, researchers use the traditional gravity model to characterize the contacts that exist between two cities. The traditional gravity model assumes ideal conditions, but these preconditions and their results often do not exist in realistic conditions. Thus, we used a modified gravity model to characterize the city contacts within a specific region. This model considers factors such as intercity complementarities, government intervention, and the diversity of the transportation infrastructure which is characterized as the transportation distance instead of the traditional Euclidean distance. We applied this model to an empirical study of city contact in the Zhujiang(Pearl) River Delta(PRD) of China. The regression results indicated that the modified gravity model could measure city contact more accurately and comprehensively than the traditional gravity model, i.e., it yielded a higher adjusted R2 value(0.379) than the traditional gravity model result(0.259). Our study also suggests that, in addition to urban-regional and metropolitan development, the complementarities of the basic functions of cities at the administrative and market levels, as well as the corporeal and immaterial levels, play very significant roles in the characterization of city contact. Given the complexity of city contact, it will be necessary to consider more relevant influential factors in the modified gravity model to characterize the features of city contact in the future.展开更多
In recent years,wetland ecological water requirements (EWRs) have been estimated by using hydrological and functional approaches,but those approaches have not yet been integrated for a whole ecosystem.This paper prese...In recent years,wetland ecological water requirements (EWRs) have been estimated by using hydrological and functional approaches,but those approaches have not yet been integrated for a whole ecosystem.This paper presents a new method for calculating wetland EWRs,which is based on the response of habitats to water level,and determines water level threshold through the functional integrity of habitats.Results show that in the Huanghe (Yellow) River Delta water levels between 5.0 m and 5.5 m are required to maintain the functional integrity of the wetland at a value higher than 0.7.One of the dominant plants in the delta,Phragmites australis,tolerates water level fluctuation of about ± 0.25 m without the change in wetland functional integrity.The minimum,optimum and maximum EWRs for the Huanghe River Delta are 9.42×106 m3,15.56×106 m3 and 24.12×106 m3 with water levels of 5.0 m,5.2 m and 5.5 m,corresponding to functional integrity indices of 0.70,0.84 and 0.72,respectively.A wetland restoration program has been performed,which aims to meet these EWRs in attempt to recover from losses of up to 98% in the delta's former wetland area.展开更多
This paper investigates the important scientific problem of river regulation strategies in the lower reaches of the Yellow River, and discusses the "geo-basis" of river regulation. The concept of a geo-basis...This paper investigates the important scientific problem of river regulation strategies in the lower reaches of the Yellow River, and discusses the "geo-basis" of river regulation. The concept of a geo-basis to river regulation in the lower Yellow River was discussed in terms of subsidence and sedimentation features of the fiver plain; channel features, erosion characteristics of the Loess Plateau and storm-flood features of the middle and lower reaches. The geographic features of the lower Yellow River have gradually changed since the Holocene but there has been no fundamental change. Based on an analysis of the geo-attributes of the lower reaches of the Yellow River, several conclusions on its river regulation were made. The release of sediment should be the first measure of river regulation because of deposition in the lower reaches. The fiver channels should be provided with adequate space for wandering in the lower reaches. The tail river should be also provided with necessary wandering space because of weak marine dynamics in the estuary area and changes in the delta. Because the erosion environ- ment of the Loess Plateau will not fundamentally change, river harnessing of the middle reaches should focus on improving the plateau morphology, which can be done by reducing the fragmentation of terrain and building a planation surface. Eco- remediation should focus on converting farmland to grassland. There may be extreme floods in the future, as has occurred pre- viously, thus an extreme flood defense system should be considered for the lower reaches. A periodic law for regulation in the Yellow River is discussed. We also discuss how the current use of the lower reaches of the Yellow River is unsustainable and it is urgent to research artificial rechanneling and the creation of new flow paths for the lower reaches.展开更多
文摘This article argues that the "sand flat-private field" pattern was the outcome of interaction between local society and national power in the course of exploitation of the Pearl River Delta. People used various orthodox cultural symbols to maintain their own economic power and political influence. Thus, this arrangement of geographical space was in reality a local power structure in a context of national identity.
基金Under the auspices of National Natural Science Foundation of China(No.41271177)Guangdong Natural Science Foundation(No.S2012010008902)
文摘In traditional urban geography, city contact research is a classic study element in city research. In general, researchers use the traditional gravity model to characterize the contacts that exist between two cities. The traditional gravity model assumes ideal conditions, but these preconditions and their results often do not exist in realistic conditions. Thus, we used a modified gravity model to characterize the city contacts within a specific region. This model considers factors such as intercity complementarities, government intervention, and the diversity of the transportation infrastructure which is characterized as the transportation distance instead of the traditional Euclidean distance. We applied this model to an empirical study of city contact in the Zhujiang(Pearl) River Delta(PRD) of China. The regression results indicated that the modified gravity model could measure city contact more accurately and comprehensively than the traditional gravity model, i.e., it yielded a higher adjusted R2 value(0.379) than the traditional gravity model result(0.259). Our study also suggests that, in addition to urban-regional and metropolitan development, the complementarities of the basic functions of cities at the administrative and market levels, as well as the corporeal and immaterial levels, play very significant roles in the characterization of city contact. Given the complexity of city contact, it will be necessary to consider more relevant influential factors in the modified gravity model to characterize the features of city contact in the future.
基金Under the auspices of Major State Basic Research Development Program of China (No. 2006CB403303)National Natural Science Foundation of China (No. U0833002,40571149)Scientific Research Foundation of Beijing Normal University (No. 2009SD-24)
文摘In recent years,wetland ecological water requirements (EWRs) have been estimated by using hydrological and functional approaches,but those approaches have not yet been integrated for a whole ecosystem.This paper presents a new method for calculating wetland EWRs,which is based on the response of habitats to water level,and determines water level threshold through the functional integrity of habitats.Results show that in the Huanghe (Yellow) River Delta water levels between 5.0 m and 5.5 m are required to maintain the functional integrity of the wetland at a value higher than 0.7.One of the dominant plants in the delta,Phragmites australis,tolerates water level fluctuation of about ± 0.25 m without the change in wetland functional integrity.The minimum,optimum and maximum EWRs for the Huanghe River Delta are 9.42×106 m3,15.56×106 m3 and 24.12×106 m3 with water levels of 5.0 m,5.2 m and 5.5 m,corresponding to functional integrity indices of 0.70,0.84 and 0.72,respectively.A wetland restoration program has been performed,which aims to meet these EWRs in attempt to recover from losses of up to 98% in the delta's former wetland area.
文摘This paper investigates the important scientific problem of river regulation strategies in the lower reaches of the Yellow River, and discusses the "geo-basis" of river regulation. The concept of a geo-basis to river regulation in the lower Yellow River was discussed in terms of subsidence and sedimentation features of the fiver plain; channel features, erosion characteristics of the Loess Plateau and storm-flood features of the middle and lower reaches. The geographic features of the lower Yellow River have gradually changed since the Holocene but there has been no fundamental change. Based on an analysis of the geo-attributes of the lower reaches of the Yellow River, several conclusions on its river regulation were made. The release of sediment should be the first measure of river regulation because of deposition in the lower reaches. The fiver channels should be provided with adequate space for wandering in the lower reaches. The tail river should be also provided with necessary wandering space because of weak marine dynamics in the estuary area and changes in the delta. Because the erosion environ- ment of the Loess Plateau will not fundamentally change, river harnessing of the middle reaches should focus on improving the plateau morphology, which can be done by reducing the fragmentation of terrain and building a planation surface. Eco- remediation should focus on converting farmland to grassland. There may be extreme floods in the future, as has occurred pre- viously, thus an extreme flood defense system should be considered for the lower reaches. A periodic law for regulation in the Yellow River is discussed. We also discuss how the current use of the lower reaches of the Yellow River is unsustainable and it is urgent to research artificial rechanneling and the creation of new flow paths for the lower reaches.
