Polycentric urban development is promoted as a planning strategy to make cities and regions more efficient and sustainable.This article reviews the emerging literature on polycentric development in China.We find that ...Polycentric urban development is promoted as a planning strategy to make cities and regions more efficient and sustainable.This article reviews the emerging literature on polycentric development in China.We find that Chinese urban regions are still largely monocentric,with emerging polycentric urban centers.There exists a geographical mismatch between urban centers identified by different metrics and composite indicators.The mechanism of polycentric urban development in China differs across cities and geographical scales,and the primary triggers include economic,institutional,and transportation factors,with a significant role of the state.Polycentric development has gained currency in planning policy in China,and these policies have contributed to polycentric urban development in well-developed regions.Furthermore,the Corona Virus Disease 2019(COVID-19)pandemic promoted suburbanization and limited people’s mobility,and polycentricity in the post-pandemic era is worthy of further investigation.This review calls for efforts for multiscale,multi-dimensional,and multi-mechanism understanding of polycentric development toward more powerful theoretical and policy contributions.展开更多
This paper develops a fine-scaled analysis in order to determine the cost and benefit of flood protection using hardened coastal structures within a large coastal segment. The probability distribution of surges and th...This paper develops a fine-scaled analysis in order to determine the cost and benefit of flood protection using hardened coastal structures within a large coastal segment. The probability distribution of surges and the relative rate of sea level rise are estimated from local tidal data and combined with detailed GIS data of all buildings to compute flood damage. Examining a heterogeneous suburban coastline of 110 km length (Branford, Connecticut), the paper defines a complete set of small segments along the coast between high elevation points. For each segment, the study determines whether the benefit of seawalls exceeds the cost and the optimal height for each wall. The analysis compares a uniform wall across the entire town, a uniform wall across only the low lying parts of the coastline, and a unique wall in each micro segment that maximizes net benefits. The uniform wall across the entire town fails a benefit cost analysis. By simply restricting the wall to the 30% of the coastline that is low lying, the flood benefits begin to exceed the cost of the walls. By carefully identifying just the low lying segments where the benefit exceeds the cost, the overall benefit to cost ratio can be increased to 3 to 1. The optimal flood protection program builds walls along only 10% of the coastline. These optimal micro segments are dispersed throughout the entire town including inland along a coastal river. The optimal elevation of the top of the walls is 2.3 m which is well below the 1/100 year storm height of 3.2 m. The benefit versus cost does not justify protection against rare but locally catastrophic storms such as hurricanes. Sea level rise increases the benefits of protection but plays only a small role in current protection decisions.展开更多
基金Under the auspices of National Natural Science Foundation of China(No.42201231,42401246)China Postdoctoral Science Foundation(No.2022M713234)International Postdoctoral Exchange Fellowship Program(No.YJ20220202)。
文摘Polycentric urban development is promoted as a planning strategy to make cities and regions more efficient and sustainable.This article reviews the emerging literature on polycentric development in China.We find that Chinese urban regions are still largely monocentric,with emerging polycentric urban centers.There exists a geographical mismatch between urban centers identified by different metrics and composite indicators.The mechanism of polycentric urban development in China differs across cities and geographical scales,and the primary triggers include economic,institutional,and transportation factors,with a significant role of the state.Polycentric development has gained currency in planning policy in China,and these policies have contributed to polycentric urban development in well-developed regions.Furthermore,the Corona Virus Disease 2019(COVID-19)pandemic promoted suburbanization and limited people’s mobility,and polycentricity in the post-pandemic era is worthy of further investigation.This review calls for efforts for multiscale,multi-dimensional,and multi-mechanism understanding of polycentric development toward more powerful theoretical and policy contributions.
文摘This paper develops a fine-scaled analysis in order to determine the cost and benefit of flood protection using hardened coastal structures within a large coastal segment. The probability distribution of surges and the relative rate of sea level rise are estimated from local tidal data and combined with detailed GIS data of all buildings to compute flood damage. Examining a heterogeneous suburban coastline of 110 km length (Branford, Connecticut), the paper defines a complete set of small segments along the coast between high elevation points. For each segment, the study determines whether the benefit of seawalls exceeds the cost and the optimal height for each wall. The analysis compares a uniform wall across the entire town, a uniform wall across only the low lying parts of the coastline, and a unique wall in each micro segment that maximizes net benefits. The uniform wall across the entire town fails a benefit cost analysis. By simply restricting the wall to the 30% of the coastline that is low lying, the flood benefits begin to exceed the cost of the walls. By carefully identifying just the low lying segments where the benefit exceeds the cost, the overall benefit to cost ratio can be increased to 3 to 1. The optimal flood protection program builds walls along only 10% of the coastline. These optimal micro segments are dispersed throughout the entire town including inland along a coastal river. The optimal elevation of the top of the walls is 2.3 m which is well below the 1/100 year storm height of 3.2 m. The benefit versus cost does not justify protection against rare but locally catastrophic storms such as hurricanes. Sea level rise increases the benefits of protection but plays only a small role in current protection decisions.
