July 2023 Catastrophic Flash Flooding in Vermont - Takeaways of the Communication and Social Science Best Practices

Catastrophic flash flooding and river flooding occurred across the state of Vermont from 7-16 July 2023. Extensive flooding to communities, washouts of numerous roads and bridges, and even the occurrence of landslides resulted in significant property losses. The most widespread and significant flood damage occurred on 10-11 July 2023, when rainfall amounts of 3 to 9 inches were observed across the state. The highest 48-hour rainfall total was 9.20” in Calais, Vermont and rainfall reports of 4 to 8 inches were commonplace along the spine of the Green Mountains and adjacent communities.

Despite damage rivaling other benchmark storms in the state - including Tropical Storm Irene in 2011 and the Great Flood of 1927 - only one direct flood-related fatality was reported. The limited loss of life can be attributed in part to NWS Burlington partner interactions well in advance of the storm, and accurate forecasts and proactive steps taken to raise awareness to the severity of the storm in the days before its onset. Confidence in the weather and water forecasts allowed a State of Emergency Declaration by Vermont Governor Phil Scott on Sunday afternoon, 9 July 2023, in anticipation of the widespread heavy rainfall in the ensuing 48 hours. The State of Emergency declaration facilitated mobilization of swift water teams and other resources from nearby states to mitigate storm impacts to the maximum extent possible.

As confidence grew in the days leading up to the historic flooding, internal collaboration with neighboring WFOs, and intra-agency partners such as the Weather Prediction Center (WPC) and Northeast River Forecast Center (NERFC) allowed for consistency in NWS messaging. On Sunday morning, July 9th, forecasters worked to coordinate a “high-risk” Day 2 Excessive Rainfall Outlook (ERO); it was the first High-Risk ERO ever issued for the BTV forecast area. Later that morning during a Vermont Emergency Management conference call, forecasters used the words “historic” and “catastrophic” to describe the flooding that was about to unfold, also stating that impacts would be the worst seen since Irene.

This presentation will detail how NWS Burlington utilized social science best practices and a historical analog to Tropical Storm Irene in 2011, leading to an early and effective emergency response for this historic event.