This issue is focused to address one of the unprecedented challenges in the context of stormwater and wastewater management in the Urban environments. These challenges commonly result from increased population growth and consequent urbanisation, as well as from ageing infrastructure and climate-change impacts. To address these challenges, large-scale deep tunnels are increasingly being implemented around the world to cope with the conveyance and storage issues arising with the collection and treatment of stormwater and wastewater. Typically, such deep tunnels have been enabled using “Drop Structures” that function to convey storm or wastewater, safely and efficiently, through substantial elevation differences incurred by deep sewer schemes.