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A Holistic Approach to Managing Flood Water

A Holistic Approach to Managing Flood Water

Heartwood Preserve, taking shape in Omaha, Nebraska is one of the largest urban spaces under development in the U.S.

By David Meyer

Setting new standards for urban improvements, Heartwood Preserve will be a unique walkable hub with a central park, a commercial district, and new housing — all connected to restored prairies and forest systems. The jewel of the billion-dollar project is an eighty-acre Greenway system featuring thirteen carefully sculpted retention basins.

This five-hundred-acre parcel of land lies within a watershed ravaged by storms — an increasingly common weather pattern. In 2019 alone, Eastern Nebraska was devastated by unprecedented flooding that cost over 1 billion dollars in property damages. The new Greenway System furthers traditional stormwater infrastructure design with a dynamic approach that will strengthen existing ecosystems, protect agricultural economies, and offer the people of Omaha an exceptional collection of amenities and experiences.

Crescent Basin #2 is already hard at work, the basin is recharging the aquifer and serving frogs, birds and all sorts of Nebraska critters

Addressing storm water challenges was a critical aspect of planning for Heartwood Preserve, but from inception, my firm, Meyer Studio – Land Architects (MSLA), was determined to go beyond capturing and managing stormwater. We saw this as an opportunity to shape a more meaningful connection between people and their natural world.

Prioritizing both aesthetics and function, we conceived a series of open spaces connected by a progression of 13 sculpted basins that will become a signature of the project. The series of limestone-clad basins will have the capacity to capture and store an estimated fifty-five million gallons — 170 acre-feet — of stormwater runoff. They have all been designed to accommodate 100-year storms with the peak discharge leaving the basins designed to mimic the pre-development agricultural field conditions.  The basins have also been designed to provide water quality treatment of the first half inch of runoff (“first flush”), allowing sediment to settle out prior to stormwater runoff entering the public sewer system.  MSLA collaborated with project civil engineers, Lamp Rynearson, and the engineers provided by the general contractor, Meco-Henne, to design the basins.

While watershed calculations and space constraints were the basis for all 13 basin designs, we worked to create a collection of distinct spaces that reflect their immediate surroundings and complement the whole sinuous form. Models helped MSLA refine the size and shape of the basins, which range from elliptical and near-perfect rounds to narrow, linear forms. These iconic spaces will change constantly. Whether full of water, dry, marshy, or frozen solid, the basin clearings will provide a range of experiences and contribute to a unique and timeless place.

Simple materials and careful craftsmanship carry through the system. A noteworthy aspect of Heartwood’s construction is the consistent use of limestone. The stone, quarried, saw-cut and split in Minnesota is largely responsible for Heartwood’s strong, timeless feel. While used throughout the project — as in parks and parkway terraces — the material is used to reinforce the walls of every retention basin. Due to the basins being close to property lines we could not always stay flatter than 3:1 slopes for basin walls and still meet volume goals. The necessary 1:1 and steeper slopes are bolstered with stone blocks that measure 2-feet tall by 2-feet deep with lengths up to 4-feet. The exposed faces of the blocks were split faced while the tops, bottoms and internal faces were saw cut to facilitate leveling and tight-fitting joints. All stonework is dry stacked and pinned with dowels where required to anchor steeply stacked units. In total, the project will use approximately 26,000 tons of stone.

A ringed allée of trees frame the largest basin, serving as a subtle counter to the surrounding native prairie and informal drifts of woodlands

To add consistency and further the formality of the forms, storm lines were routed to enter all 13 basins on axis. To call attention to the incoming water, weathered steel frames were embedded into the stepped limestone walls. Limestone rip rap extends out from the steel ‘collars’ to disperse incoming water in order to capture silt and prevent erosion. Distinctive, conical stone cairns at the low point of all the basins mask overflow catch basin structures. The overflow structures feature slots at both the 2-year and 10-year mark that allow water to be slowly released into the downstream storm drainage system.

Beyond meeting imperative water management goals, the climate response infrastructure keeps the ebb and force of nature front and center. As water and weather leave their mark, natural forces that might otherwise go unnoticed will be made visible. Our intention is to aid awareness of a changing planet and contribute to a more climate-resilient world.

Through the restoration of woodlands, wetlands, prairie, and aquifers, Heartwood Preserve’s greenways and water basins will fortify and protect Eastern Nebraska’s ecological networks for flora and fauna. In response to the site’s various microclimates, multiple native grass mixtures were formulated, ranging from water tolerant mixes for the wetlands to drought tolerant mixes for the uplands. To support an ambitious plan to plant ten thousand trees, nurseries have been studded throughout the development. Trees that had to be cut down for construction will be “re-planted” and serve as totems and precious habitat for mammals and birds.

Upon completion the Greenways will contain over fourteen miles of trails extending throughout the five hundred acres and into Omaha’s “Paths of Discovery” network. Linking into both the West Papio Trail and the 144th Street Trail, these paths will provide more continuity to Omaha’s larger multi-modal trail network, used by bike riders, families, and runners. Amenities throughout the Greenways include fire pits, shelters, picnic areas, playgrounds, and council rings.

The basins and their surroundings reveal the constantly changing landscape. The harmonious site is held together by a series of sculpted landscapes that are performative, distinctive, and ever-changing

The grand scale of the Heartwood site gave MSLA the opportunity and responsibility to create something that transcends what has been done before. This stately earthwork infrastructure and its surroundings will be dynamic public art that make both the immediate and long-term changes in our environs visible and legible.

The effectiveness of the design will be determined by its contribution to economic, environmental, and social resilience as measured by real estate value, number of jobs created, and income generated by business and tourism. While more difficult to measure, I’m certain that Heartwood Preserve will contribute to quality of Omaha life and my hope is that this approach will inspire designers, engineers and builders to collaboratively consider what could be done to foster and celebrate ecological awareness.

The Heartwood Preserve Greenway design has won four prestigious landscape and sustainability design awards: The American Planning Association, The American Society of Landscape Architect’s Northern California Chapter, The Architecture MasterPrize, and an Architizer A+ Award.

Heartwood Preserve is owned by Applied Underwriters, a global risk management company that is building its new operations campus in Omaha at Heartwood. In addition to the Greenway, Heartwood Preserve will feature 1.65 million square feet of office space, 50,000 square feet of retail , and 430 homes.

Bart Emanuel, National Director of Development & Construction for Applied Underwriters said: “These basins not only will mitigate flood risk, but are also incredible land art in an area that will be well-traveled by the public. As visitors wind their way around the Greenway water basin path, there will be various opportunities for recreation such as sand volleyball or socializing around a fire pit in the summer, and ice skating in the winter.”

Construction on the Heartwood Greenway System began in Spring 2019 and is anticipated to be completed in 2023.