Model simulations of potential contribution of the proposed Huangpu Gate to flood control in the Lake Taihu basin of China

Hanghui Zhang,Pat J.-F Yeh,Shuguang Liu,Jianchun Ye

doi:10.5194/hess-21-5339-2017

Abstract

Abstract. The Lake Taihu basin (36 895 km2), one of the most developed regions in China located in the hinterland of the Yangtze River Delta, has experienced increasing flood risk. The largest flood in history occurred in 1999 with a return period estimate of 200 years, considerably larger than the current capacity of the flood defense with a design return period of 50 years. Due to its flat saucer-like terrain, the capacity of the flood control system in this basin depends on flood control infrastructures and peripheral tidal conditions. The Huangpu River, an important river of the basin connecting Lake Taihu upstream and Yangtze River estuaries downstream, drains two-fifths of the entire basin. Since the water level in the Huangpu River is significantly affected by the high tide conditions in estuaries, constructing an estuary gate is considered an effective solution for flood mitigation. The main objective of this paper is to assess the potential contributions of the proposed Huangpu Gate to the flood control capacity of the basin. To achieve this goal, five different scenarios of flooding conditions and the associated gate operations are considered by using numerical model simulations. Results of quantitative analyses show that the Huangpu Gate is effective for evacuating floodwaters. It can help to reduce both peak values and duration of high water levels in Lake Taihu to benefit surrounding areas along the Taipu Canal and the Huangpu River. The contribution of the gate to the flood control capacity is closely associated with its operation modes and duration. For the maximum potential contribution of the gate, the net outflow at the proposed site is increased by 52 %. The daily peak level is decreased by a maximum of 0.12 m in Lake Taihu, by maxima of 0.26–0.37 and 0.46–0.60 m in the Taipu Canal and the Huangpu River, respectively, and by 0.05–0.39 m in the surrounding areas depending on the local topography. It is concluded that the proposed Huangpu Gate can reduce flood risk in the Lake Taihu basin, especially in those low-lying surrounding areas along the Taipu Canal and the Huangpu River significantly, which is of great benefit to the flood management in the basin and the Yangtze River Delta.

Highlights

The Huangpu River, located in the downstream part of the Lake Taihu basin, is the main shipping and drainage route to the port city of Shanghai in China
The concomitant storm surges will be driven into the Yangtze River estuaries to further increase storm tide levels due to the shallow waters and confined dimensions within the estuaries (Nai et al, 2004). When this coincides with the astronomical high tides, the storm tide travelling into the Huangpu River can rapidly raise water levels in rivers and possibly cause inundation of the urban areas of Shanghai
This study shows that the construction of an estuary gate at the Huangpu River is an effective measure for evacuating floodwaters and reducing peak water levels along Lake Taihu, the Taipu Canal, the Huangpu River, and the Yangtze River estuary

Summary

Introduction

The Huangpu River, located in the downstream part of the Lake Taihu basin, is the main shipping and drainage route to the port city of Shanghai in China It flows through the urban core of Shanghai, which is evaluated as one of the most vulnerable metropolises to extreme flood disasters in the world (Balica et al, 2012). The concomitant storm surges will be driven into the Yangtze River estuaries to further increase storm tide levels due to the shallow waters and confined dimensions within the estuaries (Nai et al, 2004) When this coincides with the astronomical high tides, the storm tide travelling into the Huangpu River can rapidly raise water levels in rivers and possibly cause inundation of the urban areas of Shanghai. It has been reported that along with global climate change, the frequency and intensity of typhoons have increased substantially (Qin et al, 2005)

Objectives

Methods

Findings

Discussion

Conclusion