PALEOFLOODS OF NEW JERSEY

Ideally the longest possible flood dataset would be used to determine flooding hazards, but usually only a maximum of 100 years of historic flood events are recorded by USGS gages in New Jersey and other states. Calculating the flood magnitudes of longer recurrence interval floods such as the 300, 500, or 1000 year flood based on these shorter records is problematic. A longer flood record often exists in lake sediments as these depositional basins record, albeit at a coarser resolution, inputs of terrestrial material likely corresponding to flooding events. This project cored two lakes in northern New Jersey to determine their paleoflood record. The sediment cores obtained from two lakes in northern New Jersey, Budd Lake and Swartswood Lake, were analyzed at 1 cm intervals for their water content, loss on ignition, and carbonate content. The terrigenous layers, indicating flooding events, were identified through decreases in LOI and changes in color. The paleomagnetic inclination was also measured with an AGICO JR6 Spinner and D-tech D-2000 AF Demagnetizer in order to provide a dating reference for the occurrence of terrigenous layers and to correlate them between the cores, as an alternative to radiocarbon dating. The Budd Lake core contains about 50 cm more sediment than Swartswood Lake and probably has more flooding events recorded. However, Budd Lake also contained more organic matter than Swartswood Lake. The terrigenous layers are less obvious visually in Budd Lake’s core than Swartswood Lake. 3-5 flooding events are recorded in Swartswood Lake’s sediment and 4-5 flooding events are recorded in Budd Lake’s sediment. From 0-45 cm, both cores show similar trends in decreases and increases in LOI, indicating that the flooding events were most likely a regional event. Several paleofloods were identified in the cores, suggesting that more extensive investigation would extend the current records we have on large flooding events and contribute to the better understanding of flooding events that will happen. This investigation could help put into context several recent large floods and provide better information for planning for hazards.