USING CHIRP SUBBOTTOM PROFILES TO CONSTRAIN PRE-HOLOCENE TO MODERN DEPOSITION AND EROSION IN THE LOWER DELAWARE ESTUARY

Over the last 25,000 years, the Delaware Estuary, located within the Mid-Atlantic region of the United States, has undergone substantial change as a result of sea-level fluctuations. During past lower sea level, a network of river channel systems was formed. During subsequent sea-level rise, these paleochannels were in-filled and overlain by estuarine sediments. To better understand the evolution of the past fluvial to the modern estuarine environment in the lower region of the Delaware Estuary, we analyzed recently collected chirp subbottom profiles. Sediment layers within vibracores from the study area were used to ground-truth the chirp data. Our subsurface data indicate that the paleochannels have had a strong influence on the evolution of topographic features along the estuary bottom, including modern channels and adjacent shoals. Bottom current circulation patterns in the modern estuary play an important role in transporting, eroding, and depositing near-surface sedimentary features, such as sediment waves, within the estuary’s modern channel. Our observations show the utility of having higher-resolution sonar data integrated with vibracores to further constrain previous work in this portion of the estuary. Our results are useful to policy makers and engineers in determining the future management of the Delaware Estuary, including maintenance of the navigation channel and availability of sand resources for shoreline replenishment.