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Delaware River Flooding

Delaware River Basin Comprehensive Study

Origins of the Project

Significant development has occurred on the New Jersey banks of the Delaware River in areas occasionally subject to flooding, from the 1700s to the present day. The most widespread flood event in the Delaware River Basin occurred over 50 years ago in 1955, when the northeast United States was subject to the remnants of two separate hurricanes, Connie and Diane, occurring less than a week apart. Saturated ground conditions from Connie resulted in flash flooding conditions during Diane. USACE estimated the property damages in New Jersey from this flood at $100 million. The National Weather Service has estimated recurrence of this record flood event would cause $2.8 billion in damages in the Basin in today's dollars. Although flooding of this scope and magnitude is rare, damage from more localized flooding occurs frequently. Major storm events occurred in September 2004, April 2005, and June 2006, highlighting the need for a comprehensive study of possible solutions. Several examples of flooding in specific study area communities are provided below:

Belvidere, Warren County: The floodplain in Belvidere is highly developed with residential and commercial dwellings. Although the Delaware River did not overflow its banks in Belvidere during the events of 2004-2006, several towns, including Belvidere, experienced severe flooding due to backwater effects. The Pequest River and the Pophandusing Brook both flooded due to backwater from high flows on the Delaware River. The stream flow gauge at Belvidere indicated record stages. Only the flood of record in 1955 and the ice jam of 1903 had higher stages than the 2005 event.

Phillipsburg, Warren County: Flooding has been an ongoing problem for Phillipsburg since it was settled in 1750. Flooding occurs along the Lopatcong Creek and is primarily the result of debris blockage behind bridges. During the flood events of 2004-2006, the Delaware River overflowed its banks, resulting in backwater flooding along the Lopatcong Creek. Flooding of storm sewer pipes was also a problem.

Frenchtown, Hunterdon County: Flooding has been a problem for Frenchtown since settlement of the area over 200 years ago. Frenchtown experienced flooding during all three events from 2004-2006. An old railroad embankment in the town runs along the Delaware River, and is now used as a bicycle and pedestrian path. Backwater from the Delaware River was carried under the embankment through culverts, resulting in flooding along the Nishisakawick and Little Nishisakawick Creeks. Localized excessive storm water runoff caused additional flooding landward of the embankment.

Lambertville, Hunterdon County: This is a highly developed historic community located along the Delaware River's floodplain. River flooding has inundated numerous commercial, industrial and residential structures. Major flooding of Alexauken Creek, Swan Creek, and Ely Creek resulted from backwater effects from the Delaware River, causing overflow in the creeks' lower reaches. Flooding severely damaged bridges that cross the Delaware River and link Lambertville with New Hope. Major flooding occurred in the 2004, 2005 and 2006 events, with the worst occurring during the 2005 event.

Sources of flooding in the area have included excessive precipitation from spring storms in combination with snowmelt, or fall tropical storms coming up the Delaware River, both of which cause the Delaware River to overflow its banks, as well as; tributary flooding resulting from backwater effects from high flows on the Delaware River; backflow of storm sewer systems from the Delaware River; localized excessive stormwater runoff overwhelming the existing draining system; and water overtopping the Delaware and Raritan Canal embankment, potentially leading to breaching.

The purpose of the Delaware River Comprehensive Feasibility Study - Interim Report for New Jersey, sponsored by USACE and the New Jersey Department of Environmental Protection (NJDEP), is to evaluate potential solutions to frequent flooding problems and environmental degradation as it pertains to flooding within a select portion of the Delaware River Basin in New Jersey. The study has three objectives: (1) to identify flood risk and environmental restoration needs, (2) to evaluate flood risk and environmental restoration measures, (3) to recommend flood risk management, and environmental restoration measures to be further pursued.

Based on knowledge of the areas of greatest flood damage, USACE and NJDEP mutually agreed to evaluate flood risk management along the Delaware River in the New Jersey municipalities of Knowlton, White, Belvidere, Harmony, Philipsburg, Pohatcong, Holland, Frenchtown, the Byram portion of Kingwood, Stockon, Lambertville, Hopewell, Ewing and Trenton.

The study is also investigating flooding issues and ecosystem restoration opportunities associated with the levee along the Delaware River in Greenwich and Logan Townships. Greenwich and Logan Townships are the southernmost communities in the study area and have extensively flat topography. The Repaupo (aka Gibbstown) Levee, constructed over 200 years ago for land reclamation to farm salt hay, extends for 4.5 miles along the Delaware River through the area. The levee is no longer used for agricultural purposes. Businesses and residences that did not exist when the levee was built are now located behind the levee. The original levee owner, the Repaupo Meadow Company, is now defunct and at least three commercial entities and a municipality own portions of the levee, with other portions' ownership in question.

Sections of the levee are in various states of disrepair. There have been levee breaches during storm events, resulting in flooding. The levee, originally created for agricultural purposes, is not built to manage flood risk for residential and commercial structures. No single entity has the authority and financial ability to pay for needed maintenance to the levee.


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