Climate change, sea level rise, and storm surge events are now significant factors threatening critical water and wastewater infrastructure. Extreme storm events have increased the need for the preparation required to face the challenges of climate change. In October 2012, Hurricane Sandy impacted 13 wastewater treatment facilities in New York City alone, causing millions of dollars in damage. Sandy was only a tropical storm, with a wind speed of 22.35 ms-1 (50 mi/h), when it made landfall in New York; however, it caused havoc because it combined with other local cascading events. The storm damage was caused by cascading synergistic events, including storm surge, sea level rise, and rain, rather than a singular decisive event of factor. The disaster left behind by Superstorm Sandy alone magnifies the dire need to understand the damage scenarios and consequences, and to identify resiliency plans and mitigation strategies that take into account a multitude of parameters that contributed to the intensified and devastating impacts. This work formulated the critical factors into a new concept introduced here as total water level (TWL). Using hydrodynamic models, the flood depths and elevations were calculated for various return periods and hurricane categories for coastal and riverine flooding, considering TWL to demonstrate the role of cascading events. The results show the compound effect of extreme storm events as hurricane surge combines forces with sea level rise and rainfall events; it translated into an additional 2.74-4.26 m of flooding in two studied locations.