PALEOFLOOD ASSESSMENT OF AN ABANDONED MEANDER, CHENANGO RIVER, NEW YORK

Recent large historical floods in the upper Susquehanna River basin of New York have been variously attributed as >100- to >500-year recurrence intervals. We undertook a study of an abandoned meander along the Chenango River, a tributary to the Susquehanna, to extend the record of floods into prehistoric time and evaluate their frequency and relative magnitude. We drilled an 8-meter-deep core, but recovered only 4.5 m of sediment due to compaction and loss of dominantly organic material. The upper 0.7 m that we recovered is composed principally of organic matter. One layer of very-fine sand was recovered within the organics, which we interpret as a flood deposit within the marshy fill of the abandoned channel. The organic material is underlain by 1.36 m of sediment that coarsens downwards from fine sand to pebble-sized gravel, which we interpret as a fining-upwards point bar deposit. The lower 2.5 m of the core is composed of alternating layers of silts and very fine sands, which we interpret as overbank deposits. While the core records likely flood events in the overbank deposits, the incomplete recovery prevents us from determining the complete frequency of flood events. Additional coring planned for 2013 will focus on the upper part of the sequence to more fully evaluate the paleoflood history.