Urban inundation management should take various forms to deal with different flood situations, rapid population growth, and climate change. Research on the advantages and disadvantages of grey infrastructure, such as deep tunnels and pipe networks, is necessary to apply hybrid green-grey infrastructure scientifically and efficiently. A novel urban flood model was applied in a highly urbanized region to evaluate the grey infrastructure. Green-grey approaches were also compared. The results showed that deep tunnels decreased the peak flood volume and shortened the time of peak flow. Pipe network improvements decreased the peak flood volume but did not affect the time of peak flow. However, the deep tunnels could not mitigate local inundations caused by insufficient sewer pipe capacity, whereas pipe network improvements could not mitigate inundations caused by backwater flooding. Moreover, pipe network improvements tended to generate new downstream inundation hot-spots. Green-grey infrastructures performed better than grey infrastructures for urban flood reduction. A hybrid green-grey approach was recommended. Suitable combinations of green-grey infrastructures improve the stability and effectiveness of urban flood management.

城市淹没管理应采取多种形式来应对不同的洪水情况，人口的快速增长和气候变化。研究灰色基础设施（如深层隧道和管网）的优缺点，对于科学有效地应用混合灰绿色基础设施是必要的。在高度城市化的地区，采用了一种新颖的城市洪水模型来评估灰色基础设施。还比较了绿灰色方法。结果表明，深水隧道减少了洪峰流量，缩短了洪峰时间。管网的改进减少了高峰洪水量，但没有影响高峰流量的时间。但是，较深的隧道无法缓解由于下水道容量不足而造成的局部淹没，然而，管网的改进无法减轻因回水洪水而造成的洪水泛滥。此外，管网的改进往往会产生新的下游淹没热点。在减少城市洪水方面，绿灰色基础设施的表现要好于灰色基础设施。建议使用混合灰绿色方法。绿灰色基础设施的适当组合可提高城市洪水管理的稳定性和有效性。