There are examples aplenty throughout the city of efforts to clean, capture, and slow down the flow of stormwater before it hits the sewer. One of these is the parking plaza on the southeast corner of Denny Way and Westlake Avenue.
The driving areas are flush with the sidewalks in an effort to provide a curb-less paved surface. When trying to redirect stormwater to a planting, curbs become barriers to be overcome. Yet curbs are intended to enhance safety by separating pedestrian from vehicular traffic. In this case, the only thing separating cars from pedestrians are oversized parking blocks.
The high point is a the center planting of the lot. So where does the water go? At first glance you'd think it goes straight into the storefronts of the surrounding businesses, but not so. There is a slight cross-slope at the sidewalk which directs water into the permeable paver & tree grate zone.
In fact, unlike Iowa, most residential streets around the Seattle metro area sit at a higher elevation than the buildings they service. It is common practice to have a cross-slope right before the low point, be it a retail storefront or residential driveway, to drain off the water.
Back at the center planting, the trees are quite the sight. The grove sways with great flexibility, almost perilously in the wind. I'm dying to know what kind of trees these are. I'm leaning towards some kind of birch cultivar. If you think you know what kind of tree this is, please let me know!
For those of you who enjoy identifying trees, there is a very cool website put out by the Arbor Day Foundation called What Tree Is That which can help you I.D. many tree species. They go through a fun process called taxing (there may be a joke there).