Report Release: Historical Water Bodies, Combined Sewer Overflow, and Flood Vulnerability in NJ
Authored by Jonathan DeLura
As urban areas have developed in New Jersey, some water bodies such as ponds, streams, and wetlands have been filled in, developed over, or rerouted through stormwater systems. In some cases, this process may have increased local flooding. In addition, rerouting surface water into stormwater systems has increased the amount of water flowing through these systems. During heavy precipitation events, this may increase the likelihood of combined sewer overflow (CSO) events, during which stormwater and wastewater flow untreated into local waterways. In some cases, returning these altered water bodies to their previous state may help reduce local flood vulnerability and CSO events (Morrison, 2023).
The purpose of this project is to identify and create a dataset of historical water bodies in New Jersey that have been altered by human development, with a focus on areas with a history of flooding and areas with combined sewer systems and explore the spatial relationship between these historical water bodies and both local flood vulnerability and combined sewer outfall (CSO) locations.
The dataset produced by this project may be used to inform policy initiatives aiming to reduce CSO events and local flood vulnerability in New Jersey as well as policies aiming to prevent development in, or relocate development out of, flood-prone areas in the state.
At the time of writing, a historical water bodies dataset has only been completed for Union County. The analyses and findings discussed here are specific to Union County but may serve as an example of what can be accomplished in other counties using this prescribed methodology.
Policy Recommendations
- It is recommended that New Jersey revisit the statewide Hazard Mitigation Plan (HMP) process to consider the previous location and shape of historical water bodies altered by human development as potential hazards of concern, so that counties may identify them as hazards to profile in their local HMPs.
- It is recommended that the New Jersey Department of Environmental Protection’s (NJDEP) Climate Change Related Hazard Vulnerability Assessment (CCRHVA) guidance be expanded to explicitly incorporate the analysis of historical water bodies altered by human development as potential natural hazards, so the previous location, shape, and/or path of historical water bodies altered by human development are considered by municipalities when developing CCRHVAs.
- It is recommended that returning historical water bodies altered by human development to their original state be considered a potential CSO control alternative during the CSO Long Term Control Plan (LTCP) permitting process.
New Jersey State Policy Lab, July 20, 2026