Climate Change and Flooding: A Challenge in Minnesota’s Backyard at Shady Oak Lake

Imagine you’ve found the perfect home—a beautiful lakeside property in Minnesota, nestled in a vibrant community with easy access to trails, parks, and your favorite local spots. Life here feels just right, a seamless blend of nature and urban convenience. But as the years pass, this idyllic setting reveals a growing threat — rising water levels from increasingly intense rainfall.

Climate change is usually framed as a problem for coastal communities, places where rising seas threaten neighborhoods and infrastructure. You hear about hurricanes hammering the East Coast, levees straining in New Orleans, and entire islands at risk in the Pacific. But surely, tucked away in the heart of the Midwest, you’re safe from all that. Sadly, this is no longer the case.

Back at your tranquil Minnesota home, after each heavy rainfall, the lake rises just a little more than before. At first, it’s easy to dismiss until you realize the lake has no outlet and the historical balance the lake had found between water soaking into the ground and typical rainfall has been disrupted. Even though your home was built at an originally safe elevation, the increasingly intense storms mean the lake’s floodwaters inch closer every season.

Navigating Climate Resilience and Flooding Challenges with Sustainable Solutions

In Minnesota’s own backyard, this reality became evident for Shady Oak Lake in the City of Minnetonka, during its wettest year on record in 2019. The lake sits within an urbanized 687-acre watershed, meaning stormwater accumulates rapidly, especially with heavier rainfall trends. But with no previously existing outlet, excess water remained trapped, escalating flood risks with each passing year. Previously safe elevations now faced the consequences of disrupted rainfall patterns, exposing an urgent need for sustainable action.

As a landlocked lake, Shady Oak Lake’s rising waters began flooding adjacent properties, exacerbated by increased rainfall intensities and upstream development. It was clear an outlet was needed to alleviate the flood concerns and move water downstream following extreme rainfall events. However, a straightforward solution was not easy, as simply “pushing the problem downstream” would not be viable and would impact other landowners. At the same time, the city needed to balance the recreation benefits, without prematurely moving too much water downstream, making the popular public beach unusable.

Initially, the city resorted to pumping water out, but this provided only a temporary fix. The process was noisy, inefficient, and slow, taking six months to lower water levels by just two feet. Freezing Minnesota winters further complicated this approach, making it impractical for year-round use. Similarly, a traditional gravity pipe solution was inadequate, as it would merely shift the problem downstream, triggering opposition from downstream landowners and creating permitting challenges.

Recognizing the growing threat of persistent flooding as a consistent, intensifying issue, the City of Minnetonka relied on its guiding principles of sustainability to develop a solution that balanced flood mitigation with environmental responsibility. Rather than simply managing the symptoms, they sought a smarter, dynamic system that could respond to real-world conditions without causing downstream harm. Bolton & Menk, alongside other stakeholders, designed and helped the city implement an advanced dynamic outlet system, ensuring resilience against extreme rainfall events while maintaining environmental responsibility and community needs.

A culvert with two openings surrounded by rocks and vegetation; one opening is covered with a metal grate, and the other is an open concrete pipe. A road, trees, and a blue sky with scattered clouds are visible in the background.
A new outlet was created to discharge Shady Oak Lake toward Nine Mile Creek.

A Smarter, Sustainable Approach at Shady Oak Lake

With its compass pointed toward sustainable solutions, Bolton & Menk supported the City of Minnetonka with stakeholder engagement to design a publicly acceptable gravity-based outlet system integrated with the city’s Supervisory Control and Data Acquisition (SCADA) technology. The system monitors real-time water levels at both Shady Oak Lake and downstream receiving waters, automatically adjusting flow as needed.

To actively manage lake levels, a dynamic control system was designed to:

  1. Monitor Shady Oak Lake to detect rising water levels and predict risk to nearby properties.
  2. Track water levels in Nine Mile Creek, the downstream body, to ensure safe discharge.
  3. Automate operations based on pre-approved scenarios, eliminating the need for manual intervention during extreme weather events, and preventing harm to downstream properties.

Based on the gauge readings, the SCADA system operates a valve to open or close the outlet, which discharges water by gravity through a new storm pipe to Nine Mile Creek. By telling the outlet when to open and remain closed following intense rain events, the system avoids prematurely releasing too much water downstream while also reducing the flood risk for the area surrounding the lake. Essentially, the dynamic system discharges excess stormwater from Shady Oak Lake at ‘off-peak’ times relative to Nine Mile Creek flows. This lowers the lake levels without downstream impacts and readies the lake to temporarily hold water during the next high intensity storm. The gravity-based valve system offers reliability during extreme rain events, operating automatically at night or on holidays, freeing public works staff to address other areas in town.

The Shady Oak Lake solution was accomplished with support of the Minnesota Department of Natural Resources (MnDNR), Minnesota Board of Water and Soil Resources (BWSR), Nine Mile Creek Watershed District (NMCWD), consultant Bolton & Menk, and the City of Minnetonka. This approach embraces sustainability by considering the changing environmental conditions while preserving the urban infrastructure surrounding the lake.

An outdoor scene featuring a body of water in the background, surrounded by trees and greenery. In the foreground, there is an open metal hatch on a concrete base to the left and a closed metal cabinet with visible controls or equipment to the right.
A receiving valve vault and control panel in front of Shady Oak Lake.
A view inside the valve vault of the submersible equipment at Shady Oak Lake.
A view inside the valve vault of the submersible equipment and screen designed to prevent discharge of the invasive aquatic milfoil to the downstream waters.

A Future Defined by Sustainability and Resilience

Climate-driven flooding is reshaping communities across the United States due to increasingly severe storm events. The City of Minnetonka’s Shady Oak Lake project stands as a testament to effective adaptation, combining bold leadership, collaboration, and smart engineering. It not only protects residents for generations but also builds resilience and transforms challenges into opportunities for sustainability and environmental stewardship. Shady Oak Lake is more than just flood prevention for one city; it serves as a model for Midwest communities confronting evolving climate risks, ensuring lakeside neighborhoods remain safe and prepared for the future.

Localized flooding serves as a stark reminder that climate change isn’t confined to distant coasts or remote islands. Even communities with vibrant access to nature and amenities, like those in Minnesota, must adapt. It poses real challenges, demanding thoughtful approaches to protect neighborhoods and evolving alongside changing environmental conditions, creating even stronger and more resilient communities.

A peaceful lakeside scene with clear water reflecting the blue sky and surrounding greenery. Trees, bushes, and rocks line the shore, with a small concrete structure visible in the foreground.
The influent pipe from Shady Oak Lake before it enters the valve vault.

To learn more about Bolton & Menk’s commitment to balancing progress and preservation, click here.

Smiling man with short dark hair and glasses wearing a blue shirt and dark blazer, standing by a large window. The blurred greenery outside adds to the serene ambiance as he reflects on how MATHCOUNTS creates positive experiences through challenging yet rewarding problem-solving activities.
Mike Waltman

As the municipal group leader working out of our Burnsville location, Mike manages municipal infrastructure projects and supports cities in pursuit of their goals. He has a passion for effectively managing all phases of projects, including ideation, consensus building and pursuit grant opportunities, delivering final design solutions, and implementing the successful construction of complex projects, both large and small. His goal is client satisfaction, founded in dedicated service to the public, and he works hard to make that happen.

Matt Blazer

Matt is a municipal project manager who finds the most rewarding part of any process is resident interaction and communication. Matt is driven by the challenge of finding not only an acceptable solution, but the right solution. “Very few people can impact the world we live in as much as civil engineers. Whether it’s providing reliable sewer and water to everyone, or adding a pedestrian facility to a busy road, we truly have one of the most impactful careers in the modern day.”