Imagine Ninth Street as a river. In a river, water creates curves in the landscape, flowing in a dendritic pattern from high points to low. Eddies, rapids, curves and ripples mold to their environs and are constantly in motion. On Ninth Street the river carries water, people, vehicles, and goods along its meandering path. Stormwater flowing down slope from Prospect Park to the Gowanus Canal will be channeled through luscious swales of green. Instead of running rapidly through pipes, mixing with sewage, and overflowing to the Gowanus through Combined Sewage Overflow outfalls, water percolates and filters, reducing the impact of contaminants on the canal.

The river responds to the needs of the street. The open flow of stormwater orders the street and slows traffic by adding bends in the road and widening the pedestrian realm. Sometimes the river moves rapidly and efficiently. Other times it slows and provides easy access and refuge for users. The swales of green both filter water and provide greenspace; trees offer shade and seating allows for greater social interaction. Buses have ample room to stop and corner bumpouts create space for bus shelters. Traffic lanes are fewer and narrower, prioritizing the quality of pedestrian experience.

Now imagine Fourth Avenue as a grand boulevard, with safe space for bicycling and less risk of pedestrian vehicular accidents. Instead of a truck speedway, the Avenue is a more balanced road. While acknowledging the need for a truck route to move freight around the city, the street also provides an increased bicycle and pedestrian realm. Two lanes of traffic in each direction allow for continued use by cars and trucks in a zone designated for higher speed vehicles. An elevated bikeway allows for speedy and protected bicycle travel. Narrow access roads with parking create a slower and bicycle-friendly area that acts as an extension of the pedestrian realm and as a buffer between fast vehicular traffic and other street users. Pedestrian crossings are narrow and easy to navigate; a canopy of shade trees line the street and pleasant public space reflects the greater pedestrian use of the avenue.

The river and the boulevard create livable streets. Traffic flows in an orderly way through the intersection, and cars, trucks, and bikes all have space to turn with ease. A greater percentage of the street is allotted for foot traffic and cyclist use.

When the two systems overlap, a third condition is created. Water flows through strips of permeable paving and open channels. The strips correspond with the lane designations on Ninth Street in order to minimize traffic impact. For vehicles driving on Fourth Avenue the textured paving in the intersection slows traffic. The intersection is a point of pause, a destination, a safer place to walk and cycle.