Assessing the mitigation effect of deep tunnels on urban flooding: a case study in Guangzhou, China

ABSTRACT

There are growing demands of deep tunnels to mitigate the severe urban flooding by providing a large storage capacity for excess storm runoff. This study aims to assess the flooding mitigation effect of a deep tunnel system proposed in the old downtown of Guangzhou, China, and to quantify the flooding volume difference by two storm hyetographs, the Chicago curve and the Improved Huff curve. Results show that the flooding volume is significantly reduced by a minimum of 19% and a maximum of 42% under design storms of 10- and 0.5-year return periods, respectively, when the deep tunnel system is constructed. There is a distinct spatial pattern for the mitigation effect. The best mitigation is in the west and the immediate north of the main tunnel, whereas the east does not show significant mitigation. Moreover, the actual flooding risk is likely underestimated when the Chicago curve is employed to design the storms.

KEYWORDS:

• Deep tunnel
• urban flooding
• storm hyetograph
• Improved Huff
• SWMM
• Guangzhou

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This study was jointly supported by the National Key Research and Development Program of China (#2018YFB0505500, #2018YFB0505502), the National Natural Science Foundation of China (#41301419, #41871085), the China Scholarship Council (#201806385016), and the Science and Technology Program of Guangzhou (# 201707010098).