Dallasites have been promised a park between the Trinity levees for so long, have been witness to so many plans and debates, that the idea that it might become a reality has seemed little more than a pipe dream, a rueful civic joke.

Reality has arrived, finally. On Thursday, the first legitimate vision of that park will be presented to the public in the form of a 64-foot-long, 8-foot-tall annotated cross-section that visualizes an extraordinary new landscape stretching from levee to levee.

Described as a "first look," the presentation is open to the public, and will take place at Gilley's Dallas on Thursday from 5:30 to 8 in the evening. Speakers will include the park's landscape architect, Michael Van Valkenburgh, and Brent Brown, the chief executive and president of the Trinity Park Conservancy, the nonprofit authority commissioned last May by the city to build the park.

Also speaking will be Timothy Dekker, the project leader for LimnoTech, the Michigan-based environmental engineering firm that specializes in major urban water projects.

A portion of illuminated wall plans for a park inside the Trinity River levees -- this portion shows an area along the main river channel inside the levees — is seen in a display at GoodWork (a shared co-working space) on Tuesday, Dec. 4, 2018 in Dallas. (Ryan Michalesko / Staff Photographer)

What they will show is no fantasy; there are no goofy jugglers, no hot air balloons, none of the gimmicks that have plagued so many previous false starts.

Instead, there is a presentation that joins design and science, demonstrating in sharp detail the elements and strategies that will transform the 200 acres between the Ron Kirk (formerly the Continental Avenue) and the Margaret McDermott bridges into a grand urban park.

"Dallas for a very long time has heard ideas for a park on this site and there's been a rolling collection of proposals," says Van Valkenburgh. "I hope this one seems exciting and the city gets behind it. I hope they find the thinking to be credible from a technical perspective, but this will change the way you live in Dallas."

The proposal deserves the city's full support, and in Van Valkenburgh it has a figure with credibility certified by a series of major urban waterfront park projects. In the last year, his firm, MVVA, has opened the 64-acre Gathering Place in Tulsa and the 91-acre Gateway Arch park in St. Louis, both to critical and popular acclaim. The firm, moreover, has a long history of working in spaces prone to inundation, including Allegheny Riverfront Park in Pittsburgh and Mill Race Park in Columbus, Ind.

The Trinity project is larger than any of those, and its timeline is as ambitious as its scope. Groundbreaking is planned for the fall of 2020, with an opening scheduled for 2022. To achieve that goal, the conservancy hopes to raise $100 million on top of the $50 million donated by Annette Simmons, with the park to be named for her late husband, Harold Simmons. "It's achievable," says Van Valkenburgh. "But it's going to require a seamless unfolding of approvals and regulatory bodies getting behind it."

What makes the project feasible is its essential simplicity and modesty, a character emphasized by

1 / 3Plans for a park inside the Trinity River levees as shown Tuesday, Dec. 4, 2018. The Trinity Park Conservancy (originally founded as The Trinity Trust Foundation) is developing the plan within the Trinity River corridor for Harold Simmons Park, which would be between the Ronald Kirk Bridge to the north and the Margaret McDermott Bridge to the south.(The Trinity Park Conservancy) 2 / 3Plans for a park inside the Trinity River levees as shown Tuesday, Dec. 4, 2018. (The Trinity Park Conservancy) 3 / 3Plans for a park inside the Trinity River levees as shown Tuesday, Dec. 4, 2018. (The Trinity Park Conservancy)

the cross-sectional drawing, which represents the nearly half-mile expanse between the levees.

The shifts within this landscape, although significant in nature, are relatively subtle in proportion to the immense space they occupy. The Trinity itself is widened, and given a more natural contour with relaxed banks. Relatively small variations in topography allow for backwater channels and retention areas. Alleys of trees and other vegetation are placed on elevated points, where they are safe from all but the most significant flood events.

Among the design's principal virtues is that the Trinity's ever-shifting waters are seen not as an impediment, but an attraction to be embraced. "This wants to be a place where the flooding is a programmatic element, a thing you look forward to every time you visit it," says Liz Silver, an associate principal at MVVA.

"I think what's compelling about what we're showing is that it's a really dramatic transformation, but it's achieved through a series of very reasonable moves," she says. "It's not like some crazy thing that doesn't look possible."

Portions of illuminated wall plans for a park inside the Trinity River levees are seen in a display at GoodWork (a shared co-working space) on Tuesday, Dec. 4, 2018 in Dallas. (Ryan Michalesko / Staff Photographer)

There will be fields of wildflowers, fish in the water, and birds in the trees. Flora and fauna will be selected with a mind as to what will survive within the variety of habitats and ecologies created within the levees, a catalog the architects have already begun to explore. But here it is worth noting that this environment is not natural, but man-made, and that the proposed "re-wilding" of it is something of a non-starter, as it has been artificial since the Trinity was rerouted and channelized in the 1930s.

Among the most significant design elements to be introduced is a series of new pedestrian bridges that will link east to west, providing low-altitude views and access to the park spaces below. "The floodway gets a lot more little floods than big floods," says Van Valkenburgh, "and the bridges have the advantage of greatly increasing the number of days that the park is accessible."

They will land at the tops of the levees, which will be buttressed and extended out to connect with the city. Here, easily accessible on overlooks above flood level, will be playgrounds, cafes, performance spaces, and other amenities.

The most notable aspect of the project, and what makes it possible, is what is not included: the toll road. "Not having the road was liberating, because it allowed us to start asking, 'What are the moves we should be making around the river?'" says Silver. "That kind of a conversation was impossible when the road was a part of the plan, because so much of the plan was oriented to what the road needed in order to be constructed."

This design, it should be noted, did not simply materialize out of thin air from the faraway offices of a name-brand architect. It is very much the park that Dallas wanted, its elements and contours shaped over decades of debate and, more directly, a series of public workshops led by the Trinity Park Conservancy.

The future of the project is very much dependent on the abilities of the conservancy's director, Brent Brown. He is the right, and perhaps only, person for this job, an architect with a unique combination of political dexterity and design acumen, and with a record of building not just for the city's well-to-do, but for its neediest, as the former director of the nonprofit BC Workshop.

He will have his hands more than full, and his work must now be focused in several directions at once. The design, as it stands, is by no means a finished product; it is merely a cross-section, though a revealing one. In the next months, it will need to be developed, in cooperation with the public and any number of public and private entities.

So too, will he need to keep his eye on broader issues: how the park will be accessed; how neighborhoods will be insulated from the inevitability of rising real estate costs; and how it will be paid for and maintained, to name just a few. But these are good problems to have.

"This is an insane opportunity," says Van Valkenburgh. "It's the coming together of a new Dallas."

Now Dallas just needs to come together to build it.

Mark Lamster is the architecture critic of The Dallas Morning News, a Loeb Fellow at the Harvard Graduate School of Design and a professor at the University of Texas at Arlington School of Architecture.