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Density Gradient

Cities are coming back across the US for many reasons. The unsafe, dirty urban core of legend is being replaced by funky, hip neighborhoods with character and charm. Life in the city can be good, now that the perma-haze of pollution has been tamed. Transit helps make life more relaxing and even cheaper. Young people in particular find revitalized cities to be affordable and great places to meet their mate and then raise kids.

The movement owes a lot to New Urbanism, junking the old industrial model for cities as centers for jobs and emphasizing attractive, functional places to live. We’ve learned a lot. But if there is one flaw in this model it’s the constant emphasis on higher and higher density. There’s always a place for high density in the urban world, of course, but it doesn’t work everywhere.

A better way to look at what makes cities great is a model based on the density gradient – a gradual increase towards the core that is economically and aesthetically sustainable.

The bad old days.  But we also still do this.

The bad old days. But we also still do this.

When highway construction was the rage at the end of the twentieth century many urban cores were ringed with freeways. Access to the jobs at the center would encourage growth, the theory went, and the houses in the way were only a nuisance. They were easily replaced with large towers that held the same number of people more “efficiently” – which is why so many public hi-rises line urban freeways to this day.

There are many reasons why this massive destruction of the urban landscape didn’t work. One way of looking at their folly, however, is an understanding of the importance of a density gradient, which is to say a gradual increase in both aesthetic and population density as you approach the urban core.

Why is this important? Humans like the feeling when things make sense. A building jutting out much taller than anything around it is a jumble. It visually doesn’t seem to belong. It’s the architectural equivalent of being rude and arrogant, asserting itself above the world around it.

This may seem like a strange assertion, but consider what happened to the urban core and the first ring of neighborhoods around it in cities all across the US when the freeways came through. These “dead zones” created havoc not simply next to the highway but miles away as the gradual density gradient that grew up naturally was interrupted.

The natural density next to a freeway? Zero. The next block over? Nearly zero.  And so on.

Density Gradient Explained

How the Density Gradient Theory explains the abuse of the urban landscape during the freeway construction era.

The result became an urban core that requires massive subsidy in order to maintain the height that city pride demands. Around this rotting core stood blight, defined as old buildings far larger than they should be for their circumstances, far too expensive to maintain with cheap rent and often torn down to create parking lots.

We can see the net effect as equilibrium was reached here in St Paul, where the neighborhoods around the core are actually the lowest in population density:


Population density in St Paul as per the 2010 census. From city-data.com.

This effect is explained easily by the basic principle of a density gradient:

The goal of urban planning is primarily to encourage a gradual, sensible density gradient that is economically and aesthetically sustainable.

When this rule is not followed in urban planning, land use eventually suffers and no amount of intervention and subsidy can create a stable neighborhood over the long haul.

The Rochat-Louise-Sauerwein Block on West Seventh

The Rochat-Louise-Sauerwein Block on West Seventh

The description of how the density gradient theory works above may appear to be nothing more than a history lesson. Certainly, the mistakes of freeways and other dead zones are not repeated with the same brutality any longer. But other mistakes are made to this day. New Urbanism is often taken to mean high density mixed-use developments regardless of whether they make sense or not in the existing urban fabric.

As a critic of New Urbanism, I like to point out that the principle difference between Old Urbanism and New is that the former simply happened and the latter is carefully planned. I consider this to be strong criticism because the designs of well meaning people with a lot of education cannot simply assert their will on a city.

What, exactly, is “density”? In population terms it’s easy enough to map out, but in aesthetic terms it’s harder to describe. It varies some from one city to the next, too. But here in St Paul we can see that the existing urban landscape has shorter buildings away from the core and taller close to it. What is probably more important is the ratio of street width, including setbacks, to the height of the buildings around it.

Along an 80 foot wide street like Randolph you won’t find anything taller than three stories, or 30 feet. That ratio of about 2.5 to one holds consistently away from Downtown.  Things get a bit taller along West Seventh as you approach Downtown, where buildings are actually taller than the street is wide:

Section Streetscape Ratio
Outer Ring Greater than 2.5
Inner Ring 2.5 to 1, gradual
Core Less than 1
The Opus development at Seven Corners.

The Opus development at Seven Corners.

A good example of the density gradient planned into a new building comes to us in the Opus design for Seven Corners. The 6 story (60 feet) height is not as wide as the 80 feet in front of it on West Seventh, a ratio of 1.3 that tells you that you aren’t in Downtown quite yet – but close. That same project would make no sense down at Randolph, where a height of 3 stories would probably be a reasonable maximum.

This project will help us re-weave the torn urban fabric that was ripped up by decades of urban removal projects that were done without regard for the density gradient. It should be considerably more sustainable over the long haul – and is being built without any government subsidy entirely at market rate.

How do we make more sustainable, livable cities? One important consideration is the density gradient, which is to say that any new project has to fit in with the old in a way that makes sense. There is no one approach and higher density is not always better. New Urbanism has to respect the old urbanism and have a light touch if it is to continue to be an effective tool for improving our cities.

16 thoughts on “Density Gradient

  1. Once again, theory loses to reality. New Urbanism is full of a lot of bunk that has been used to justify huge corruption (subsidy). But you didn’t really explain why your theory is better than theirs.

    • I think that’s a bit harsh. What we see, IMHO, are a lot of project being done by people who are applying an ideology rather than responding to their environment. I’m calling for a better and wider feel for the city before asserting a development.

  2. Several interesting ideas here. I am doubtful that “high density” should be an end in itself. But if one thinks so, is there an appropriate upper bound? If so, what is it? Are humans really well suited for living in towers, hundreds of feet up?

    • I think there is very much an upper bound, although some people do like living in high density towers. It’s a matter of how much of that stuff there is from what I can see.
      A city should have a wide range of housing options and a lot of greenspace. It has to run from a lower density to a higher one, and what those two terms mean will vary from one city to the next. But a balance is always going to be important and that has to be respected if its going to remain stable.

  3. The gap between the neighborhoods and downtown is huge in St Paul. I don’t see any reason to go downtown at all but I go just about everywhere else in the city. It’s a great place to live but not because of downtown.

      • Yes, but how can that happen when the freeways continue to be expanded and construction of transit alternatives seems largely gridlocked? Perhaps we are making progress in creating alternatives to auto commuting, but those physical barriers will remain. Can anyone seriously imagine removing freeways in Minnesota? I think the discussion is mega-important, especially since our real-world urban pols seem preoccupied with cutting deals more than with strategic thinking.

      • We can’t remove freeways, but we can cover them. What I am saying here points to what should cover freeways, too – not open space, but development. Yes, the most prime land for development may be between the Capitol and Downtown!
        Strategic thinking has never ruled urban planning, despite many attempts by good people. But we do know a lot about what works and we are making progress.
        I do believe that a fairly light hand in planning is a good thing. It’s a matter of creating the appropriate urban infrastructure – which naturally includes transit. Developers really don’t try to do stupid things that often, at least not without massive subsidy. Without TIF, for example, Downtown St Paul would be a lot smaller and funkier. It’s worth remembering.

  4. Density Gradient is new to me. I’ve thought about density a lot lately as it relates to the consequences of Light Rail. Freeways divide, and so does LRT with fences and rails except at the stations.

    • I should have put up a warning label:
      Crackpot Personal Theory Ahead!
      Seriously, I know Opus among other developers thinks about this, but it has never been written down the way I did it. A city has to make sense in order to be stable, and density gradient is one way of thinking of that. Large projects in the middle of neighborhoods always fail eventually – and there’s a good reason. They just don’t belong.
      LRT can divide, yes, when it’s done badly. There was no excuse for what happened on University. Even if you insist on LRT on that street it could have been done better.
      Mind you, if it was run down the middle of I-94 we could have constructed stations on the bridges at Snelling, Dale, Lexington, etc that bridged the “dead zone”. They could have included some retail space like coffee huts. By doing so we could have erased the major gaps that separate St Paul along the freeway.
      I am saying that such a plan would have been good urban planning vs what was done by definition. Re-weaving the urban fabric and restoring an appropriate density gradient has to be a priority for all planning, IMHO.

      • Where ever the theory came from, not bad. Your theory may indicate the best way to think about siting LRT would be where needed density already exists, or perhaps is desired locally, ie. where it will be physically built. Suppose that is why the feds call the siting and mode decision the Locally Preferred Alternative. To bad the planners seem to be able to define ‘local’ in a sense that is really is more regional.

      • Thanks!
        And yes, if you apply this perspective the proper role for LRT becomes rather obvious. It supports high density within about 1/4 mile of where it is built, so you can go ahead and do that.
        I have an editorial coming out in the Community Reporter on this, but if for example we have LRT on railroad tracks and we can redevelop the ADM/Omaha site that would be a good place for a station and some higher density. It could play off the Brewery and gradually taper back a bit, just a bit, to Randolph. It would all make sense there.
        That is one way of thinking about all of this stuff and how to encourage a city that makes sense. I use the phrase “economically and aesthetically sustainable” for a good reason – I think they are the same thing.

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