A RECORD OF FLOODING HISTORY AND DEVELOPMENT FROM OXBOW LAKES, CENTRAL PASSAIC RIVER BASIN

The Passaic River, in northeast New Jersey, lies within a drainage basin of 935m². It is fed by the Pompton, Rockaway, Whippany, and Saddle Rivers. The river flows north and then southeastward before emptying into the Newark Bay. Historical records as far back as the 1700’s document the Central and Lower Passaic River’s frequent floods, the greatest being a 100 year flood event in 1903, which had a maximum discharge of 35,700 cfs (average annual discharge from 1945-1970 ~1080 cfs). While the river’s low average gradient of 6.9 feet/mile contributes to flooding issues, higher frequency of major flooding events is likely a result of urbanization, which has been shown to increase runoff, discharge and bank stability. Areas along the Passaic became heavily industrialized, beginning with Paterson, which in 1791 became the nation’s first industrial city. The river’s proximity to NYC also brought extensive development of railroads, highways, and communities for city commuters. Development in the past two decades has affected the flooding patterns of the Passaic. This relationship was determined by examining the flood records, stratigraphy, total organics, and mercury concentrations of the Central Passaic River floodplain.

Three complete cores of two meters each were obtained from oxbow lakes within the Great Piece Meadows, a relatively undeveloped floodplain in the Central Passaic basin. The organics sampled and dated (in progress) using radiocarbon dating to provide a time frame for core evidence of flooding events. The oldest organics (198 cm depth) dated to ~3600 yrs B.P. and the youngest (104 cm depth) dated to ~2460 yrs B.P. In the upper 30-55 cm of the cores, increases in mercury concentrations were measured to detect atmospheric mercury deposits, a record of coal burning and the start of industrialization. Potential preindustrial levels ranged from ~130-35 ng/g. Mercury fluctuations were also analyzed as a flood indicator, since large influxes of sediment dilutes concentrations. Grain size analysis and total organic carbon were also analyzed. These core observations and analyses are currently being compared to flood and discharge data in order to determine how urbanization has affected flooding.