Ann Arbor showcased improvements to West Park Sunday that included large swaths of native prairie and wetland plantings meant to cleanse rainwater runoff from North Seventh Street, as well a pair of orange steel trees, a new public art installment.

West Park was closed from March to October 2010 so stormwater and recreational and improvements could be completed, city park planner Amy Kuras said.

A four-hour event Sunday was West Park’s official re-opening ceremony. Events included speeches from public officials and a performance from the Ann Arbor Civic Band and others in the renovated 1930s-era bandshell. The event also served as a day of appreciation for hundreds of city volunteers who help each year to clear city parks of invasive species and keep the parks clean.

But nearby residents, while complimenting the numerous improvements, wondered if stormwater improvements meant to improve water quality into Allen Creek, which flows under the park in pipes, made flooding on North Seventh Street worse during recent spring rains. They say they’ve asked the city to explain what’s going on, and they can’t get answers.

Numerous improvements were made to address flooding at the park, Kuras said. The Ann Arbor City Council approved the project in 2009, allocating almost $1.4 million from its Stormwater Fund. Overall, the improvements cost about $1.8 million, Kuras said.

Recreational improvements include pathways, a new pond, bench seating built into the hillside surrounding the band shell, and organic community gardens from Project Grow.

Two branches of Allen Creek run under and meet directly under West Park, Kuras said. The new native planting areas, or bioswales, were planted above the underground creek, which has been contained in pipes under Ann Arbor since the 1920s. A new pond in an area of the park that naturally flooded anyway is now home to lots of toads and frogs.

Enhancements like these are meant to make dry areas of the formerly soggy park drier, and wet areas wetter, Kuras said.

North Seventh Street was totally flooded during storms, residents said. They blame a new drain configuration that was done at the same time as the stormwater improvements for West Park. Under the improvements, stormwater runs directly into the two new bioswale areas, above ground. Before, it drained into the underground Allen Creek.

Kuras said the above-ground drainage helps clean the water before it reaches the Huron River.

Residents want to know why a new drainage feature called a swirl concentrator eroded land in a section of the park near North Seventh Street. It's currently fenced off.

Susan Johnson lives off of Seventh Street near the park.

“It doesn’t work when there’s a hard rain,” she said.

Her daughter Molly, 9, loves the new pond in the park. But she compared her street to “white water rafting,” as her mom shared her opinions on the new drain configuration.

City Councilman Mike Anglin, D-5th Ward, said 81 basements flooded in his ward since rain picked up in April.

According to Anglin, the city, county and contractor who installed it can’t come to an agreement over whose job it is to fix the busted “swirler” off of North Seventh Street. Nothing will happen to fix the swirler problem until a decision is made, he said.

"We're working through all that," Kuras said.

The abnormally heavy spring rains flooded other sections of Ann Arbor, too, she said, such as on Depot and Chapin streets nearby.

"When we have as storm system that doesn’t have the capacity to carry the water from the huge storms we’re having, that’s the big picture reason," she said of flooding around Ann Arbor.

Juliana Keeping covers general assignment and health and the environment for AnnArbor.com. Reach her at julianakeeping@annarbor.com or 734-623-2528. Follow Juliana Keeping on Twitter