No abstract

In the context of climate change and rapid urbanization, urban pluvial floods pose an increasing threat to human wellbeing and security in the cities of China. A valuable aid to managing this problem lies in understanding the roles of environmental factors in influencing the occurrence of pluvial floods. This study presents a spatial analysis of records of inundated streets in the inner city of Shanghai during 1997-2013. A geographically weighted regression (GWR) is employed to examine the spatially explicit relationships between inundation frequency and spatial explanatory factors, and an ordinary least squares regression (OLS) is used to validate the GWR results.Results from the GWR model show that the inundation frequency is negatively related to elevation, pipeline density, and river density, and is positively related to road/ square ratio and shantytown ratio. The green ratio is another significant explanatory factor for inundation frequency, and its coefficients range from -1.11 to 0.81. In comparison with the OLS model, the GWR model has better performance as it has higher R 2 , and lower corrected Akaike information criterion and mean square error values, as well as insignificant spatial autocorrelation of the model residuals. Additionally, the GWR model reveals detailed site-specific roles of the related factors in influencing street inundation. These findings demonstrate that the GWR model is a useful tool for investigating spatially explicit causes of disasters. The results also provide guidance for policy makers aiming to mitigate urban pluvial flood risks.

Abstract:A valuable aid to assessing and managing flood risk lies in a reliable database of historical floods. In this study, a newspaper-based flood database for Shanghai (NFDS) for the period 1949-2009 was developed through a systematic scanning of newspapers. After calibration and validation of the database, Mann-Kendall tests and correlation analysis were applied to detect possible changes in flood frequencies. The analysis was carried out for three different flood types: overbank flood, agricultural waterlogging, and urban waterlogging. The compiled NFDS registered 146 floods and 92% of them occurred in the flood-prone season from June to September. The statistical analyses showed that both the annual flood and the floods in June-August increased significantly. Urban waterlogging showed a very strong increasing trend, probably because of insufficient capacity of urban drainage system and impacts of rapid urbanization. By contrast, the decrease in overbank flooding and the slight increase in agricultural waterlogging were likely because of the construction of river levees and seawalls and the upgrade of agricultural drainage systems, respectively. This OPEN ACCESSWater 2015, 7 1809 study demonstrated the usefulness of local newspapers in building a historical flood database and in assessing flood characterization.

This study of Shanghai analyzes the city's emerging patterns of residential settlement in 2010. Most previous research on China focused on central city patterns, but by 2010 urban development in major metropolitan areas was taking place predominantly in the suburbs. The analysis re‐examines and extends previous studies of the level of segregation by various key population characteristics, showing that the highest segregation is found in the suburban ring, where original villager residents are now joined by an influx of migrants from other regions and by intracity movers. We probe the sources of the segregation pattern in multivariate analyses at two scales—an innovative analysis at the level of individuals that shows how people's citizenship status, occupation and education affect the type of housing that they are able to live in, and jointly contribute to their location in the metropolitan area. We show that the patterns attributable to the market reform period mostly did not supplant the socialist urban structure, but rather used it as its foundation. Segregation today can be attributed less to current class inequality than to state policies in the distant and recent past that have determined when, where and for whom housing is built.