Sediment deposition from Tropical Storm Lee in the upper Chesapeake Bay: field observations and model predictions

Episodic flood and storm events are important drivers of sediment dynamics in estuarine and marine environments. Event-driven sedimentation has been well-documented by field and modeling studies. Yet, few studies have integrated field observations and modeling results to overcome the limitations inherent in both techniques. A unique opportunity to integrate field observations and model results was provided in late August/early September 2011 with the passage of Hurricane Irene and the remnants of Tropical Storm Lee in the Chesapeake Bay region. These storms differed in their timing, track, and impact on the Bay region - Hurricane Irene was primarily a wind/resuspension event, whereas TS Lee was a hydrological/deposition event, with the second largest discharge of the Susquehanna River on record. Because these two storms occurred within a relatively short period of time, both are potentially represented in the sediment record obtained during rapid-response cruises in September and October 2011. The resulting sediment deposit was recognized in cores using classic flood-sediment signatures (fine grain size, uniform ⁷Be activity, physical stratification in x-radiographs) and was found to be <4 cm, thickest in the upper Bay. Model runs conducted for TS Lee generally agreed with these estimates. One exception with physical stratification but no ⁷Be activity appears to be due to extreme wave activity during Hurricane Irene. Integration of observations and modeling in this case greatly improved understanding of the transport and fate of flood sediments in the Chesapeake Bay.