Case Studies > Haddam Demonstration Site > Rain Garden > Winter Performance of Rain Gardens

Winter Performance of Rain Gardens

We often receive questions about how well rain gardens will perform in regions with cold winters, and specifically where there is significant frost in the soil. Two years of monitoring data at the Haddam site has shown that overall, less than 1% of inflow from the roof overflowed from the garden. The remaining water either percolated through the soil and left the underdrain (about 94%), or was evapotranspired (about 5%).

Winter performance was not reduced. In general, when there was heavy snow, there was not much melted runoff. However, when melted runoff did flow from the roof, the garden was able to accept it. The reason for this is that although there was measureable frost in the garden, when melted runoff entered the garden, the porous, organic nature of the media was conducive to a rapid thaw. This allowed the water to infiltrate into the rain garden soon after runoff began. This phenomena has also been documented at a research rain garden at the University of New Hampshire.

A recent rain at the Haddam rain garden after freezing temperatures and snow was captured on video. Click here to view the QuickTime clip.

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