When Tropical Storm Irene ripped through Vermont five years ago, it dumped as much as eight inches of rain in 24 hours. “Vermont Strong” became a rallying cry as we pulled ourselves and our neighbors out of the mud and rubble to collectively rebuild our communities. The five-year anniversary of this disaster can be a cause for celebration. Vermonters are better prepared to respond to future intense storms.
Click to watch our video above to find out how Vermont can protect its communities from future storms like Irene, then read the blog below to find out more.
But the anniversary should also be a time of self-examination. Irene revealed that many of our homes, businesses and roads are vulnerable to flooding and erosion damage during storms. It’s worth asking why our rivers caused so much damage, and what we can do to avoid similar loss of life and property in the future.
Vermont’s mountainous landscape means that when rainwater falls, it rushes down the steep slopes and builds up in the valley floors, causing our rivers to rise and speed up. A river’s natural response to this is to overflow its banks into its floodplain, where the rushing waters can spread out and slow down. But many of Vermont’s floodplains have been developed with houses, buildings and roads. To protect those assets, we’ve had to confine numerous rivers to straightened channels with concrete and stone, and in doing so we have disconnected the rivers from their floodplains.
But it turns out that confining a river completely within its channel to stop flooding doesn’t make us safer. In fact, it’s just the opposite: Irene caused extensive flood damage in large part as a result of how much we have straightened our rivers. Our misguided efforts to protect property have radically increased the erosive power of our rivers, because they run deeper and faster through their narrow channels. Imagine watering a garden with a hose, then putting your thumb over the nozzle; the water suddenly shoots through the reduced opening. The same is true of rivers that we cut off from floodplains and confine to narrow channels. We didn’t lose 1,000 homes and 200 bridges during Irene because of standing water damage; rather, houses were literally yanked off their foundations, and bridge supports were wrenched out by the sheer force of the channelized rivers.
One answer to this problem is to avoid putting ourselves in harm’s way in the first place. If rivers are given room to move and access to the floodplain, they naturally maintain a “least erosive” form over time. They run slower during big storms, and they wreak less havoc to property along the river.
The Vermont Rivers Program, housed within the Department of Environmental Conservation, has created a first-in-the-nation statewide mapping system that delineates so-called “river corridors” to show the minimum space that rivers need to flood and achieve this least erosive form. With these river corridor maps, communities can see a shaded area around the river where it doesn’t make sense to build new structures. If we choose to build in the river corridor, we make new commitments to armor the streambank to avoid flooding, and we exacerbate erosion and risks to life and property downstream.
Irene showed us the vulnerability of our riverside property. It taught us that rivers need space to move during storms.
These river corridor maps took years of surveying and analysis to complete, and Vermonters are fortunate to have this information at our disposal for wise land-use development. But such a tool is only as good as the use we make of it. Right now, too many communities across the state continue to build new houses and other buildings in the very areas we should be keeping accessible for the river to flood.
Some municipalities have adopted rules restricting development within the local river corridors. But five years after the devastating wake-up call of Irene, an astounding 73 percent of communities have not adopted such protections. (Is yours one of them? Find your community here.)
Continuing to build in harm’s way is a bad bet. We will be struck by another Irene, just as Louisiana is dealing with the tragic aftermath from the Katrina-like storm that hit Baton Rouge this month, causing deaths and serious flood damage. Vermont has experienced, on average, one federally declared flood disaster each year for the past 20 years. And climate scientists predict that rainstorms will be more frequent and more intense in our region due to climate change.
Irene showed us the vulnerability of our riverside property. It taught us that rivers need space to move during storms. And we learned that there are dangerous consequences if we confine the river. Now let’s continue forward with what we’ve learned, and start using river corridor maps to inform sensible land use decisions so we quit building in the river’s way.
To a great extent, this isn’t happening at the local level. Houses are being rebuilt on the very same riverbanks as where they were washed away by Irene. Perhaps river corridor protection standards should be mandatory. Perhaps it’s time for the state to play a larger role. Regardless, action is needed to protect our river corridors from more development. Being “Vermont Strong” means we can rise to meet this challenge. We have before, and we should again here.
This blog was originally published in Vermont Digger.