HOW UNUSUAL IS TROPICAL STORM IRENE? A CASE STUDY OF STORM DEPOSITION IN LITTLEVILLE LAKE, HUNTINGTON, MA

In order to prepare for extreme weather events in the future it is important to understand the recurrence frequency and characteristic erosional and depositional patterns of past storms. Reservoirs upstream of flood control dams provide a perfect natural laboratory to study deposits from these events because the timing of reservoir impoundment provides a definitive start point for trapping sediments. This study uses Tropical Storm Irene, August 2011, as a natural experiment in the differences between extreme and typical storm events. Seven lake cores were taken from Littleville Lake, Huntington, MA in July 2013, and the Tropical Storm Irene layer was identified using markers determined by previous studies. The Irene layer and the bottom of the lakebed, created by the closure of Littleville Dam in 1965, act as time markers from which Littleville Lake sediment accumulation rates can be established. Using this time series the Spring Flood of 1987 can be estimated in the cores and deposits compared to Tropical Storm Irene deposits. Our analyses compare mineralogy (determined from X-ray diffraction), organics, mercury, grainsize, and potassium and zircon concentrations throughout the cores to quantify differences between the typically deposited sediment and sediments deposited during extreme events, such as Tropical Storm Irene and the Spring Flood of 1987. Preliminary results suggest that in comparison to other sediment in the cores, Tropical Storm Irene sediment was potassium and organic rich while being mercury poor. Discharge data from a gauging station just downstream of Littleville Lake show that biannual flooding is common, but discharges are not as extreme as during Tropical Storm Irene. However, comparing Tropical Storm Irene to the Spring Flood of 1987 shows that Tropical Storm Irene sent less water down the Westfield River. Future research will include analyzing APHRODITE precipitation data from Tropical Storm Irene and the Spring Flood of 1987 to further quantify the differences between the two storms.