By Theresa Vander Woude, Clean Lakes Alliance


By the time leaves have started to fall in Dane County, most of us have tucked away swimsuits and beach towels for the year. The lakes are too cold to swim in and too liquid for winter sports.

This fall, Clean Lakes Alliance and the Village of DeForest partnered to tackle one of our lakes’ biggest headaches: nutrient pollution from fall leaves. In particular, we wanted to answer this question: How can we encourage residents to rake leaves OUT of the streets, when so many people are used to ignoring them? The second, crucial, caveat was: Can this be done at an affordable cost per pound of phosphorus reduced?

Photo credit: Theresa Vander Woude

This pilot project, which was funded in part by a grant from the Natural Resources Foundation of Wisconsin, was spurred by information indicating that leaf management may present a big opportunity to reduce urban phosphorus pollution to the lakes.

What is phosphorus?
Phosphorus is a nutrient found in soil, manure and leaves that encourages plant growth. It is one of the main drivers behind smelly, and sometimes toxic, algal blooms. Less phosphorus runoff = clearer, healthier and better-smelling water.

When leaves steep in rainwater, they leach out phosphorous and create this “leaf tea,” which easily finds its way into storm drains and eventually into the lakes. Photo credit: David Thompson

Most people don’t know that leaves are such a problem for our lakes. Even those who do know aren’t sure what to do about it! Our leaf management pilot in DeForest used social marketing principles, using prompts and reminders for tasks that residents agreed to do. It was partially modeled on a similar project done near Lake Wingra in 2014 and is designed to be replicable and scalable throughout the watershed.

What was the baseline?

A benchmarking survey, completed in 2014, indicated that most area respondents either do nothing with the leaves that fall in the street or assume that the Village takes care of them through street sweeping. However, most respondents also identified “protecting lake health” as a primary factor influencing their leaf-raking decisions, indicating a window of opportunity for behavior change through education.

What were the results?

Did the pilot efforts succeed in getting more people to pull out the rakes and clear leaves from street gutters? In short, yes it did. Monitored participation rates in areas that received the full strength of outreach jumped from a pre-pilot baseline of seven percent participation to 18 percent participation. These results are encouraging as they indicate that voluntary action can be increased at least 2.5-fold using a fairly simple combination of outreach strategies.

In addition, attitudes and self-reported participation changed significantly:

  • Before the pilot, 44 percent of respondents self-reported that they were “usually” or “always” clearing leaves from the street gutter.
  • During the pilot, the self-reported percentage jumped to about 66 percent.
  • Concerning the future, 83 percent of respondents indicated they will “usually” or “always” attempt to maintain a leaf-free street gutter.

This finding is very important as it indicates that results could build year over year as actions start to catch up to attitudes, and actual participation catches up to what is self-reported. With baseline observed participation so low (seven percent), and such encouraging intentions for the future (83 percent), there’s nowhere to go but up!

Natalie Trueman, CLA intern, sweeps leaves to quantify the amount of debris in the street gutter. Photo credit: Susan Fret

And the costs?

Costs for the 14 actions to clean our lake outlined in the 2012 Yahara CLEAN Strategic Action Plan range from $25 to $860 per pound and average at $216 per pound. With modifications, given changing social norms and if used in communities with a denser mature tree canopy, costs for a clean streets outreach program as piloted in DeForest could fall to as low as $276 per pound. For communities that want to adjust or improve their leaf management policies anyways, adjusting programs to reflect new best management practices and outreach strategies for healthy lakes should be a no-brainer.

The full project report is now available on our website for those interested in detailed results.

What can I do on my property?

Next fall, and even this spring, just remember this equation: Leaves + rain + asphalt = major nutrient overdose to the lakes.

The important thing to remember, whether you shred, mulch, compost, bag, sweep or just rake, is that anything you can do to keep your leaves away from hard surfaces is a plus. Since storm sewers go directly to the lakes, it’s especially important to keep leaves out of the streets. Even small amounts of phosphorus can fuel algae blooms in our lakes, so it’s never too early to get out and rake.

Thanks to Dane County, participating residents received a free sign to display in their yard. Photo credit: Susan Fret

Through the Yahara CLEAN Strategic Plan for Phosphorus Reduction, our community has set the goal of preventing 4,100 pounds of phosphorus runoff into our lakes through urban leaf management by 2025. With one pound of phosphorus capable of producing 500 pounds of algae, those reductions could have a huge impact on our lakes.