It’s beginning to look a lot like…Stormwater!

The days are at their shortest and winter is finally here.  So light a fire, grab a cup of hot cocoa, and settle down for…our guide to winterizing your stormwater BMPs.

(1) Keep Those Pervious Surfaces…Pervious

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The ground tends to freeze in the winter, which can reduce infiltration rates even in areas that usually drain well. Luckily, there are things you can do to prepare these surfaces to STAY pervious all winter long. If you have pervious pavers or pavement throughout your community, it’s important to make sure they can drain well. If water cannot drain, this not only makes your BMP less effective, but can also damage the pavers and cause cracking as trapped water freezes and expands.

First, make sure that you perform routine maintenance such as street sweeping and/or running a vacuum truck before an expected freeze so dust and debris do not become trapped and cause clogs.

Next, and we cannot stress this one enough, when it comes to sand, salt, and chemical treatments: just say no!  Your pervious system is designed to allow water (i.e., melted snow/ice) to drain; the treatments we apply to traditional impervious surfaces will work against a previous system, will lead to clogging, and will make the BMP less effective. In addition, any treatment that does not remain in place will only add to the pollutant load to your local waters.

(2) Stabilize Green Infrastructure

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During the winter months, green infrastructure such as bioswales and rain gardens might not be at their greenest, but this does not mean we forget about them! It’s important to perform seasonal maintenance to ensure the proper functioning of these BMPs.

First, you’ll want to physically remove any leaf litter and  plants that will not over-winter. Dead and decaying plants are likely to be washed away during storm events, which can clog storm drains and release excess nutrients into local waters.

Next, protect what’s left! Add a bed of mulch around surviving plants to keep them protected from the cold and keep the overall surface impervious, just be sure to keep all inlets and outlets clear of debris while applying the mulch layer.

(3) Be Prepared for Different Flow Patterns

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Stormwater BMPs are typically designed for rain storms. Winter storms are different (see: Snowmelt: Stormwater’s Evil Twin).

Snow does not hit the stormwater system right away. It just sits there, accumulating away until the temperature rises and then BOOM! We go from zero to flash flooding conditions.

There are some maintenance measures you can make to ensure your BMPs are prepared for this onslaught.

First, and just like during hurricane season, you’ll want to visually inspect your BMPs, clear any debris blocking inlets or outlets, and draw down levels in retention ponds wherever possible. Next, keep an eye on what’s going on! Remote flow monitoring systems allow you to keep tabs on how water is moving throughout your system so you can properly manage BMPs, plan preventative maintenance as needed, and avoid those unhappiest of holiday surprises: water bursting out of manholes.

At StormSensor, we’ve developed a remote monitoring network of sensors and cloud-based software designed to track water depth, velocity, and temperature throughout your stormwater system. We also pull local weather data so all the information from your system is correlated with precipitation in real-time.

And, just in time for the holidays, we’ve added a new feature to our weather offerings: Snow! Our real-time data charts will now display local snow totals along with liquid equivalents (i.e., snowmelt!). Having snowfall timing and totals available right along with stormwater system conditions will aid in maintenance and capacity planning and response during the winter months.

About the author

Suzie Housley

Stormwater Scientist

Talk stormwater with suzie@stormsensor.io Suzie has over a decade of experience in the Stormwater industry including both government and academic work. She leans on her experience to meaningfully interpret scientific studies and government policies to communicate a practical message. Suzie lives just outside Nashville, TN and gets outside whenever she can to explore nature with her husband and two small children.