Spatial Heterogeneity Analysis of Short-Duration Extreme Rainfall Events in Megacities in China

Qi Zhuang,Zhengzheng Zhou,Shuguang Liu

doi:10.3390/w12123364

Abstract

Given the fact that researchers require more specific spatial rainfall information for storm flood calculation, hydrological risk assessment, and water budget estimates, there is a growing need to analyze the spatial heterogeneity of rainfall accurately. This paper provides insight into rainfall spatial heterogeneity in urban areas based on statistical analysis methods. An ensemble of short-duration (3-h) extreme rainfall events for four megacities in China are extracted from a high-resolution gridded rainfall dataset (resolution of 30 min in time, 0.1° × 0.1° in space). Under the heterogeneity framework using Moran’s I, LISA (Local Indicators of Spatial Association), and semi-variance, the multi-scale spatial variability of extreme rainfall is identified and assessed in Shanghai (SH), Beijing (BJ), Guangzhou (GZ), and Shenzhen (SZ). The results show that there is a pronounced spatial heterogeneity of short-duration extreme rainfall in the four cities. Heterogeneous characteristics of rainfall within location, range, and directions are closely linked to the different urban growth in four cities. The results also suggest that the spatial distribution of rainfall cannot be neglected in the design storm in urban areas. This paper constitutes a useful contribution to quantifying the degree of spatial heterogeneity and supports an improved understanding of rainfall/flood frequency analysis in megacities.

Highlights

Extreme rainfall is a crucial driver of flood and waterlogging, especially in urban settings where there is a fast hydrological response and high catchment variability [1,2,3]
It shows that the magnitude of extreme rainfall increases from north China to south China, which is paired with the geographical locations of the four cities
We present a comprehensive framework to analyze the spatial heterogeneity of rainfall in four megacities in China

Summary

Introduction

Extreme rainfall is a crucial driver of flood and waterlogging, especially in urban settings where there is a fast hydrological response and high catchment variability [1,2,3]. More strong evidence shows that spatial heterogeneity has quite an impact on the hydrologic response [17]. Both peak flow and runoff volume can be influenced by different rainfall distribution patterns [18,19]. Segond [15] found that spatial heterogeneity of rainfall could decrease the performance of the urban runoff model. This finding was supported by Zoccatelli et al [20]. Zhu et al [21] even found that rainfall spatial structure is more important than a temporal structure for drainage areas larger than approximately 2000 km. More specific analysis in rainfall spatial heterogeneity is required for hydrological analysis in cities [22,23,24]

Objectives

Methods

Results

Discussion

Conclusion