Using Green Stormwater Infrastructure for Flood Resilience

Vermont has seen its share of floods. Vermont is a state of mountains and valleys with most of our village centers, downtowns and roads built in valleys near rivers.

5 years ago this August, Tropical Storm Irene rolled through the green mountain state, dumping 5 to 10 inches of rain over the course of a day. Roads washed away, homes and business flooded. The entire state was impacted by this storm. Some areas of the state were completely cutoff because roads and bridges had been washed away. But with the Vermont-can-do spirit, we began to rebuild. That meant tearing down what was left and relocating to higher ground in some cases.

Downtown Waterbury saw a significant amount of flooding, especially around the state of Vermont office complex. What was once a mental hospital in the early 1900s it was decommissioned and was converted to office space. During Tropical Storm Irene water came rushing through old underground tunnels long forgotten. It also came over the banks of the Winooski river right up, and through, the doors of the state office complex.

5 years later state employees are beginning to repopulate the corridors of those buildings. Around 300,000 square feet of building area was taken down, 1,500 square feet was restored, and 85,000 square feet was built in the same area.

Inside the courtyard in the redesigned state office complex in Waterbury

Inside the courtyard in the redesigned state office complex in Waterbury.

The rebuilding of the state office complex focused on resilience, the ability to bounce back after some form of disturbance. The new design of the complex focused on flood resilience. We know that this area will flood again, but with better planning and design, most of the water should be stopped in the parking lot, before it even reaches a building.

Green Stormwater Infrastructure (GSI) practices were installed on site to capture runoff from the site. 350-600-foot grass swales treat runoff from the impervious surface area, the parking lots and roof tops. Maintenance of these systems is pretty simple. The reconstructed office buildings were built to 10 inches above the 500-year flood mark. An 800-foot vegetated area was planted along the Winooski river. 1,000 smaller shrubs and trees were planted and a 100-foot buffer along the river was created to allow natural succession to occur. 225 trees were planted around the campus itself, representing 25 different species.

It is inevitable that we will see flooding on the scale of Tropical Storm Irene again, but building resiliently can keep us protected down the road.