Understanding New England Riverine Flooding: A Hydroclimatic Perspective

In the heavily populated region of New England, perennial riverine flooding poses a significant threat to life and property. Damage to infrastructure, interruption to trade and commerce, and the displacement of individuals, families, and communities in the wake of significant flood events serves as the motivation to better understand the hydroclimatic controls contributing to such incidents. Previous work has suggested that in New England in particular, there are relatively weak correlations between common climate indices (i.e. ENSO or the NAO) and flood occurrence. Here, through the combined utilization of instrumental river gage observations from the Hydroclimatic Data Network GAGESII dataset and both the NCEP-NCAR Reanalysis I and ECMWF ERA5 reanalysis datasets, we not only verify the lack of correlation between flood occurrence and common climate indices, but we also uncover the existence of a statistically significant pattern in anomalous 500mb geopotential height that exists at the initiation of moderate and major New England flood events. This pattern is especially prominent during the spring-time flood events and is indicative of mid-latitude frontal systems serving as the atmospheric triggering mechanism for these floods. We then extend this work to quantify the extent to which surface conditions (i.e. soil moisture and sea surface salinity) and atmospheric precursors, like moisture flux and mid-latitude storm origination, exist in the weeks and days leading up to flood crest. Understanding how fronts transfer moisture from the atmosphere to the surface provides an important foundation for evaluating how mid-latitude systems play such a significant role in New England peak flows and further exacerbate riverine flood events.