The Great Vermont Flood of July 2023

How a complex and long duration flood event came to be

Introduction

Catastrophic flash flooding and river flooding occurred across much of Vermont in early to mid-July 2023. The most widespread and significant property damage occurred as a result of prolonged heavy rainfall on July 10th and 11th, when rainfall amounts of 3 to 9 inches were observed across the state over 48 hours. The greatest storm totals were as high as 9.20", with 4 to 8 inches common along the spine of the Green Mountains and in adjacent communities. Washouts of numerous roads and bridges occurred along with land and mudslides. The runoff of excessive and widespread heavy rain caused rivers to swell, inundating many communities after rainfall ended, especially along the Lamoille and Winooski rivers. Among the towns impacted was the state capital, which drew national attention. Rainfall at the Montpelier airport measured 5.28” on July 11th, marking the wettest calendar day since records began in 1948. This narrowly beat the previous record of 5.27" set with Tropical Storm Irene in August 2011. Considering this event occurred only 12 years later, many Vermont residents could refer to Irene as a reference point.

Rainfall map from Tropical Storm Irene in northern New York and all of Vermont.

The last widespread, significant flood event in Vermont was Tropical Storm Irene.


Precursor Events and Lead up

During the month of June, a major pattern change took place, with a wetter pattern taking hold as an upper level low pressure system became established to our northwest. Because of this, our region was under deep southerly flow and subtropical moisture was in place leading to several periods of moderate to occasionally heavier rainfall, especially from eastern New York into Vermont. There were several periods of persistent rainfall during the month of June. The two most significant periods were from June 12th to 18th and again from the 24th to the 27th. These systems greatly increased ground moisture levels such that the soil’s capacity to absorb repeated rainfall was lessened significantly.  By the end of the month, rainfall departures were above normal for the entire state of Vermont.  

Rainfall map for June 2023 for northern New York and all of Vermont

Rainfall amounts in June were well above normal, with several locations in central and eastern Vermont seeing as much as 7 to 10 inches of rain.

On July 7th, another round of showers and thunderstorms with torrential rain affected portions of Vermont and northeastern New York. Isolated areas had up to 3-5” of rainfall. This resulted in areas of flash flooding, quite severe in some locations. The hardest hit areas in Vermont were Killington and Bridgewater. Numerous road washouts occurred during the afternoon and evening hours with the most notable event being a large landslide which blocked US Route 4 in the town of Killington, shown in this remarkable picture.

NWS Burlington worked in close collaboration with neighboring Weather Forecast Offices (WFOs), the Weather Prediction Center (WPC) and Northeast River Forecast Center (NERFC). This allowed for consistency in NWS messaging. Following the flash flooding on Friday July 7th, new Flood Watches were issued across Vermont on Saturday July 8th for the July 9-11 period by WFOs Albany and Burlington. In anticipation of potentially historic flooding, on Sunday morning (July 9th), forecasters on duty coordinated with WPC for a Day 2 Excessive Rainfall Outlook (ERO) of a “HIGH-risk”, depicted on the US map. This was the first HIGH-risk Day 2 ERO ever issued for the Burlington forecast area. Later that morning during a Vermont Emergency Management (VEM) 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 since Irene. The consistency in messaging across NWS operational units responsible for heavy rainfall and river forecasts added confidence and facilitated the lifesaving actions that followed in conjunction with federal, state, and local partners.


The Storm Arrives

Hourly Radar Loop from midday on July 9th through midday on July 11th

The main event of July’s widespread flooding would start somewhat innocuously on the afternoon of July 9th. Isolated thunderstorms developed first across south central Vermont, increasing in coverage as they lifted north. Although these cells were not particularly severe, they did produce heavy rainfall, and the first Flash Flood Warning was issued at 3:13 PM for central Essex County in northeast Vermont. More widespread heavy rain overspread eastern NY and much of Vermont through the evening hours, with rainfall amounts of 1.5 to 3.25 inches falling in just an hour or two.

Flash Flood Warning included Route 14 in Woodbury which flooded Sunday evening

Three more Flash Flood Warnings and one Areal Flood Warning were issued throughout the afternoon and evening hours, with flooding reported in Woodbury, and Calais, Vermont, and in Redford, Saranac, and Altona in New York.


Unfortunately, this served as just a precursor of things to come. After a brief respite in the rain late in the evening, round after round of moderate to heavy rain drenched the region over the next 36 hours. Flash Flood Warnings continued to be issued through July 10, right into the early morning hours of July 11. As heavy rain streamed into Vermont, NWS Burlington posted dire warnings on social media which unfortunately soon proved all too true.

NWS Burlington staff emphasized the life-threatening and catastrophic nature of the flooding.

Reports of catastrophic flooding started to come into the National Weather Service early on July 10, first in Windsor and Rutland Counties, and then progressing northward along with the heavy rain. As the steady rain continued, flash flooding started to give way to river flooding; the Winooski and Lamoille watersheds were particularly hard hit, with record stages reached at Montpelier and Johnson.

Hydrographs crested at record level for gauges in Montpelier (Winooski River) and Johnson (Lamoille River)

The last River Flood Warning wasn’t canceled until the early morning hours of Thursday, July 13.


Observed rainfall was so high in such a large portion of central Vermont that a modified color table was created to plot the data.

By the time rain finally abated early on the 11th, 2 to 6 inches of rain had fallen across portions of northeastern New York and western Vermont, while 4 to 8 inches with localized 9 inch amounts occurring along and just east of the spine of the Green Mountains. All told, the National Weather Service issued 8 Areal, 16 Flash, and 17 River Flood Warnings just from July 9-11.


Below are all reported flash floods in Vermont during the July flooding events.

Vermont July Flash Floods


Damage Assessment and Cleanup

FLASH FLOODING -> BARRE, LUDLOW

By the morning of Wednesday, July 12, most of the flood waters had receded. Now was the time to assess the impacts this devastating event had on area communities. Hardest hit by flash flooding were communities in the southern Green Mountains including the towns of Ludlow, Plymouth and Weston, and in the City of Barre in central Vermont. Other communities experienced varying degrees of flash flood impacts, but Ludlow and Barre were particularly affected.

Damage occurred in many Vermont communities due to flash flooding, including Ludlow, Barre, and Plymouth (from left to right).

RIVERINE FLOODING -> WINOOSKI AND LAMOILLE

Riverine flooding was also severe in some portions of the state. The crest on the Winooski River in Montpelier was the second highest on record with most of the downtown business district inundated by several feet of water. Only the Great Flood of 1927 saw higher levels in the city. Downstream in Waterbury, many homes were inundated and the State Office Complex access was blocked by high water. Further north, communities such as Johnson and Jeffersonville also suffered severe damage as the Lamoille River crested at or above record levels. Even in the far north, a few communities such as Coventry did not escape the flood waters.

River flooding put many towns underwater, including Coventry, Johnson, and Montpelier (from left to right).

IMPACTS TO INFRASTRUCTURE -> ROADS, LANDSLIDES, HOMES/BUSINESSES

At the height of the flooding on the morning of July 10, over 100 state and federal highways were either damaged or closed by high water shown on the map. The number of secondary and dirt roads affected by flooding was even greater, though a full count was not available at the time of this narrative. 

One particularly bad outcome of the torrential rainfall was that it led to a saturation of the soil to fairly deep levels which created numerous areas of slope instability, and in some cases landslides. A particularly severe landslide, shown here, occurred along Route 62 in Barre, VT. Luckily, no injuries were reported.

A Vermont geologist observes evidence of landslide formation in Barre.

Route 131 Bridge in Cavendish collapsed due to high flood waters of the Black River.

A gorge formed under the collapse of a railway in Ludlow. As of this writing, Vermont State Geologists have documented over 70 discrete slope failures or landslides of varying severity and potential threat.

COMPARISONS TO IRENE

No two storms are the same, an often used old weather adage. This could be said about hurricanes, snowstorms, or in this case, rainstorms. After this most recent storm, there were many comparisons of what just happened to those that occurred during Tropical Storm Irene in August 2011. Accordingly, the National Weather Service in Burlington made two rainfall maps to illustrate the similarities and differences between the two historic events. From the maps, and the accounts of flooding and damage, clear similarities and differences can be seen. Overall storm totals were similar across portions of south central Vermont, particularly in Rutland and Windsor Counties. While local impacts certainly varied in this region, in general, the total damage to infrastructure was on par with Irene. Differences were more notable in northern Vermont, where the July 2023 rains and damages exceeded those in Irene, and in far southern Vermont, where Irene’s impacts were more severe. Although in New York, communities in the Ausable River basin such as Keene and Au Sable Forks fared much worse in Irene than in this most recent storm.

A side-by-side comparison of rainfall totals from the two events.

NWS BURLINGTON DAMAGE ASSESSMENT SURVEYS

In the following days staff from NWS Burlington along with support from other local and regional NWS offices conducted post storm damage assessment surveys across the state. The surveys focused on three primary regions: 1) south central Vermont including areas in the Otter Creek and Ottauquechee River Valleys, 2) central Vermont including areas in Barre, Montpelier and Waterbury in the Winooski River Valley, and 3) north central Vermont in the Lamoille River Valley from Johnson downstream to Jeffersonville. Given time limitations, not all communities could be surveyed, but other agencies such as the U.S. Geological Survey also performed extensive surveys across the region. As a result of NWS Burlington’s work and feedback from town officials during the surveys, new flood levels and/or impact statements were incorporated along stretches of these waterways. This new information will help local residents plan and take appropriate actions should future flooding be forecast for their communities.

NWS Hydrologists observing high water marks during storm surveys.


Reflections

The Great Vermont Flood of 2023 was historic and difficult to forecast, but National Weather Service forecasters and their partners worked together to mitigate as much loss of life as possible.

"This was a high-end event rivaled by few other flooding episodes in Vermont in the past century. My recurring thought is that the widespread flooding across our state occurred with a weak surface low that never deepened below 1005 millibars! Think about that and how much more difficult decision making is when there isn't an easily identifiable mid-latitude storm or a tropical cyclone to point to on a weather map. Despite this - we always have an obligation to turn science into service.”

Peter Banacos, Science Operations Officer at the Burlington, VT, National Weather Service Office

“As the event unfolded, we have taken an all hands on deck philosophy, and every single member of my staff has done so willingly. Five people voluntarily canceled leave to help out at the office. At one point while we were monitoring tornadic weather, we ran out of workstations!”

Gabriel Langbauer, Meteorologist-In-Charge at the Burlington, VT, National Weather Service office

“There isn't a magic wand - even the best forecasts and warnings can't prevent a flooding event from occurring. However, the ability to substantially mitigate storm impacts and work with our federal, state and local partners to save life and property is central to the NWS mission. We saw those mitigation actions in full effect before and during the events of July 9th, 10th, and 11th, 2023. I couldn't be more proud of the way all those pieces worked cohesively - the product of many years of building trust and relationships with emergency managers, swift water rescue teams, and many others who were directly managing the response as events unfolded across so many of our communities."

Peter Banacos, Science Operations Officer at the Burlington, VT, National Weather Service Office

Colchester Technical Rescue in operation to help with Montpelier flooding.

“As the morning of 10 July 2023 unfolded we quickly realized the severity of the flooding after receiving reports from Vermont Emergency Management of swift water rescue teams performing 2nd story evacuations across Rutland and Windsor Counties and our team of forecasters promptly upgraded to our first ever Flash Flood Emergency, which will remain in my memory for a long time.”

Brooke Taber, Lead Forecaster at the Burlington, VT, National Weather Service office

While there was fortunately minimal loss of human life, this event was still extremely devastating and life-changing to many across Vermont. Many saw their life’s passions and finances washed away in the flooding.

“At least 7,000 acres of farmland in Vermont alone have been lost.”

Scott Waterman, spokesperson for Vermont Agency of Agriculture, Food, and Markets via the New Lede

“All the sheds and coops were destroyed, all the birds drowned.”

Angela Murphy, Chicken Farmer in Proctorsville, VT, via Vermont Public

Before and after photos of a community garden plot.

"We have to cover it out of pocket. But there's no pocket to pay [a quarter million dollars] out of."

Erica Hayes, daughter of Cambridge Market Village owners, via WBUR

"In my 20 plus years of forecasting weather across the North Country, I have never witnessed such a prolonged and devastating combination of flash and river flooding across the state of Vermont during the Great Flood of the Summer of 2023. The monthly record rainfall of over 12 inches at our Capital City was truly unprecedented, along with the catastrophic damage to infrastructure, homes and businesses throughout the state, which surpassed tropical system Irene in 2011."

Brooke Taber, Lead Forecaster at the Burlington, VT, National Weather Service office

Downtown Montpelier Water Rescue on July 11th.

"The Great Flooding of July 2023 reminded us that heavy precipitation can strike anywhere, especially across our mountainous terrain, and is not only associated with tropical systems. We were also reminded that droughts and flooding can occur within the same year as we saw in 1927, 2011 with Irene, and again in 2023. Finally, we were reminded that we need to understand the landscape around our homes and livelihoods in order to better prepare for the climate hazards that will occur."

Lesley-Ann Dupigny-Giroux, Professor and Vermont State Climatologist

Another piece of why this flooding was so damaging to Vermont is the way it followed Hurricane Irene by just 12 years.

"After Irene, we wanted to mitigate and we thought it was a 100-year event. Being hit so closely to Irene shows that we need to make progress over time. It is not something we can change overnight or even in 10 years. It is just something that you have to keep working on."

Doug Farnham, Chief Recovery Officer of Vermont, via ClimateWire

A stand up paddleboarder floats through downtown Montpelier.

This story map was created by the National Weather Service in Burlington, Vermont. The above content was written and compiled by meteorologists Maureen Hastings, Jessica Neiles, Jessica Storm and Seth Kutikoff, and by hydrologist John Goff.

Special thanks goes to Plymouth, VT Emergency Services; Pat Moore; Killington, VT Emergency Management; Seven Days newspaper; United States Geological Survey; The University of Vermont; Vermont Community Newspaper Group; Town of Coventry, VT; the Vermont Center for Geographic Information; WCVB-TV; Andrew Woodham; and Emma Cotton of VTDigger.

NOAA - National Weather Service

StoryMap created by NWS Employees

The last widespread, significant flood event in Vermont was Tropical Storm Irene.

Rainfall amounts in June were well above normal, with several locations in central and eastern Vermont seeing as much as 7 to 10 inches of rain.

Hourly Radar Loop from midday on July 9th through midday on July 11th

Flash Flood Warning included Route 14 in Woodbury which flooded Sunday evening

NWS Burlington staff emphasized the life-threatening and catastrophic nature of the flooding.

Observed rainfall was so high in such a large portion of central Vermont that a modified color table was created to plot the data.

Below are all reported flash floods in Vermont during the July flooding events.

A side-by-side comparison of rainfall totals from the two events.

Colchester Technical Rescue in operation to help with Montpelier flooding.

Before and after photos of a community garden plot.

Downtown Montpelier Water Rescue on July 11th.

A stand up paddleboarder floats through downtown Montpelier.