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Maintaining your stormwater and green infrastructure is essential in the fall. This season brings new drainage challenges, thanks primarily to falling leaves.

Historically, fallen leaves in urban areas didn’t significantly impact water quality. Property owners would traditionally burn leaves on bonfires, turning them into potash for soil.

However, bans on urban leaf burning from the 1970s changed this dynamic, and cities wanting to improve air quality started offering curbside pickups.

Intuitively, fallen leaves seem natural and unlikely to cause significant problems. But that’s not the case. Street-side “leaf litter” contains high quantities of phosphorus and nitrogen that can cause algal blooms if dissolved in surface runoff rainwater.

The problem can be serious. For example, the city of Toledo in Ohio experienced massive blue-green algae overgrowth in 2014 that deprived local bodies of water of oxygen, leading to mass die-offs. Falling leaves on the street fell into basins, releasing their nutrients into rainwater that entered rivers and lakes.

U.S. Geological Survey Researcher William Selbig studied the content of stormwater runoff between 2013 and 2015 in Madison, Wisconsin. He found that leaves were the primary source of nitrogen and phosphorus entering water bodies, usually as detritus from overhead tree canopies. The research concluded that one of the best ways to control algal blooms was to remove leaves from areas prone to stormwater runoff. Cutting the level of stormwater nutrient loading was essential, it appeared.

The main goal of stormwater and green infrastructure maintenance in the fall is to prevent leaves and other plant matter from entering the system. These approaches improve water quality, reduce the risk of harmful algal blooms, and help prevent blockages and backups in stormwater drainage systems. Here’s what to do:

Remove Leaves From Streets And Catch Basins

First, maintaining stormwater and green infrastructure facilities in the fall requires removing leaves from streets and catch basins. That’s because these urban features often lead directly to streams and rivers. Moreover, leaves can clog drainage systems, leading to flooding.

Keep Leaves Off Driveways And Other Hard Surfaces

Next, you’ll want to keep leaves off driveways and other hard surfaces. That’s because their non-permeability increases the risk of dangerous runoff. Again, rainwater can dissolve nutrients from leaves and flow directly into nearby freshwater bodies instead of absorbing into the soil.

Keep Leaves Away From The Road If Using Curbside Leaf Collection

If your area has curbside leaf collection, keep leaves away from the road. Place your leaf pile on top of the grass outside your home. If it rains, the soil beneath the leaves will absorb some excess nutrients, reducing harmful runoff.

Placing leaves three feet from the road should reduce the amount of rain entering the road and falling into storm drains. Unless the rain is heavy, the total amount of nutrients released from the leaf pile should be minimal.

Rake Leaves Into The Street Just Before Leaf Collection

You can also minimize surface runoff by raking leaves to a collection point near the official collection time. This reduces the risk of them being rained on.

Use Leaves As Compost

Another way to protect storm drains and prevent environmental damage is to use leaves as compost. Raking and confining them to your composter dramatically reduces runoff and enables you to retain more nutrients in your garden.

Leaves contain carbon, nitrogen, phosphorus, potassium, calcium, magnesium, and other trace elements that plants need. As such, they make excellent compost. Beneficial microbes decompose them over several weeks into nutrient-rich plant matter you can use for your beds or lawn.

Put Down Two To Three Inches Of Mulch In Your Rain Garden

You can also protect your green infrastructure by putting down two to three inches of mulch in your rain garden. Adding non-compacted mulch reduces soil erosion in rain events by slowing down the speed at which it passes through.

Just ensure your mulch is heavy enough to protect your rain garden. If it is too light, it can easily wash away.

Check Sediment Levels In Your Rain Garden

Finally, ensure you check sediment levels in your rain garden. Use a shovel to remove any unwanted buildup if they are too high.

Conduct Preventative Maintenance Activities

In summary, fall brings unique challenges to stormwater maintenance. However, simple approaches, such as controlling leaf fall, can help significantly. The main goal is to prevent leaves from clogging systems or their nutrients from causing harmful algal blooms the following summer.

If you need assistance with stormwater maintenance, inspection, or compliance reporting for your facilities, contact the stormwater maintenance specialists at Muller, Inc, via their website. Muller’s team of certified stormwater professionals is experienced with all types of stormwater facilities, Best Management Practices (BMPs), and Low Impact Development Techniques (LID).