This is where the name "Euclidian" zoning arises. Euclidian zoning entails neat separation of land uses. "Mixed-use" properties, combining residential, office, and retail perhaps, would not be allowed under a strict Euclidian zoning code.
Most planners today realize the utility of zoning but lament the modernist interpretation of zoning represented by the Euclidian manner. Corner stores, live-work units, even clean industry surrounding housing--all have gained acceptance as essential parts of a varied, diverse urban fabric. Recently, urban planners have been looking for a way to regulate land that does not stifle the way cities were meant to work.
Enter Form-Based Zoning.
Rather than merely regulate the uses of structures, form-based zoning looks at the appropriateness of scale, design, height, etc. to the urban environment. It's a relatively new concept, pioneered by New Urbanists like Andres Duany, and has been applied in a few cities now (Petaluma, California was one of the first).
Now, St. Louis may be jumping in on the game.
Central West End Midtown Development is nearly finished with its form-based zoning code for its service area--the southern portion of the Central West End and parts of Midtown. Read more at the Washington University Medical Center Redevelopment Corp.'s blog.
Here is an excerpt from the Building Envelope plan (click to enlarge):
I think this is a wonderful effort for the Central West End, Midtown, and St. Louis. I will be eager to see more of the details, such as how design is to be regulated, but this seems like a good start.
If I had one major criticism, it would be, of course, the parking. Requiring one off-street parking space per residential unit seems a little high for a truly urban neighborhood like the Central West End. It might make more sense to make one space the maximum allowed parking rather than the minimum. I am also wondering what strategy neighborhood residents chose to pursue: the modified existing envelope or the contextual envelope. The former would have allowed for more high-intensity development, especially on Lindell, Forest Park, and Vandeventer. The latter would be more cautious and preservation-minded, keeping almost all historic structures and preserving the scale of neighborhoods as they are today.
The form-based code should certainly block, say, a CVS from tearing down a group of buildings for a suburban store with a drive-through (which, of course, almost happened). It should also not allow for the rebuilding of McDonalds and Arby's in their usual forms, which already did happen.
This code should be strong and urban, solidifying the Central West End/Midtown as St. Louis's most urban experience. I am definitely eager to see the final product.