Alexander’s Distribution of Towns


In a recent post, I analyzed what it would look like to apply the first pattern of Christopher Alexander‘s A Pattern Language to North America. This pattern, titled Independent Regions, created 50 new, small nations or regions within what is today the United States and Canada. The next thing I wanted to try was applying Alexander’s second pattern, The Distribution of Towns, to one of those new regions. The pattern reads:

If the population of a region is weighted too far toward small villages, modern civilization can never emerge; but if the population is weighted too far toward big cities, the earth will go to ruin because the population isn’t where it needs to be, to take care of it.

Therefore:

Encourage a birth and death process for towns within the region, which gradually has these effects:
1. The population is evenly distributed in terms of different sizes- example, one town with 1,000,000 people, 10 towns with 100,000 people each, 100 towns with 10,000 people each, and 1000 towns with 1000 people each.
2. These towns are distributed in space in such a way that within each size category the towns are homogeneously distributed all across the region.

This process can be implemented by regional zoning policies, land grants, and incentives which encourage industries to locate according to the dictates of the distribution.

apl2diagramtowns of 1,000,000 – 250 miles apart
towns of 100,000 – 80 miles apart
towns of 10,000 – 25 miles apart
towns of 1,000 – 8 miles apart

However, as discussed in the previous post, not all regions that meet Alexander’s population criteria automatically meet his spacing criteria when you move from Pattern 1 to Pattern 2. Several regions are too large and sparse, while several more are too small and dense.

Click to enlarge.

Click to enlarge.

So to analyze Pattern 2 without worrying about redistributing the population of the regions until they were the right size, I wanted to pick one of the “Goldilocks” regions that is already about the right size. I went with the Washington DC Region.

Click to enlarge.

Click to enlarge.

Now for the distribution part. Let’s say that we have a region, Region A, with capital city City 1 in its center.Diagram1-01Alexander recommends one very large city per region, so we’ll assume that City 1 has a population of about a million and that it’s the only city of it’s scale in the region. Our first step is to identify our cities of 100,000 people. While Alexander recommended making these cities 80 miles apart, I used 72 miles to simplify the math a little bit. So we want to make sure that these cities of 100,000 are 72 miles from City 1, as well as from each other.Diagram2-01Next we want to identify our towns of 10,000. Again, I fudged Alexander’s math a bit, and identified towns that are 24 miles (1/3 of 72) from any larger cities or from each other.Diagram3-01And finally, we want to identify towns of 1,000 people, eight miles from any larger town and from each other.Diagram4-01That’s what it looks like in an ideal world. However, in the real world, we’re not starting with a blank slate, and rather than founding new cities that are perfectly spaced from DC, I wanted to identify existing cities located in the right place. When you do that, it looks like this:

Click to enlarge.

Click to enlarge.

What this technique doesn’t consider, however, is why cities are located where they are: largely, access to resources, and access to transportation. They aren’t distributed evenly across a landscape; they’re bunched up in the places that have access to mineral, agricultural or intellectual wealth, and places that have access to ports, railroads, and highways. Disregarding this truth about cities means that some cities that are not located the right distance away from one another can get hosed. Case in point, Richmond, a city of over 200,000 people at the center of a metro area with over 1.2 million, because it isn’t spaced correctly relative to DC, is relegated to the 10,000 people tier, meaning that a huge population would be resettled to areas like Tappahannock (current population 2,397) or Powhatan (current population 49) which are spaced correctly.

Also, by using Alexander’s spacing suggestions, one does not arrive at his suggestion for how many towns there should be. Based on this distribution, you end up with one town of 1,000,000, eight towns of 100,000, 45 towns of 10,000, and 319 towns of 1,000. That adds up to 2,569,000 people. But in the last pattern, we determined that the Washington DC Region would have a population of 8,917,843. So where are the other 6 million plus people living?

The answer to that actually comes from another pattern, number 5 in Alexander’s book, Lace of Country Streets:

The suburb is an obsolete and contradictory form of human settlement.

Therefore:

In the zone where city and country meet, place country roads at least a mile apart, so that they enclose squares of countryside and farmland at least one square mile in area. Build homesteads along these roads, one lot deep, on lots of at least half an acre, with the square mile of open countryside or farmland behind the houses.

Alexander doesn’t specify how wide this “zone where city and country meet” is, and if we’re got small cities every eight miles across an entire region, it would almost follow that these zones fill in the rest of the space between towns. If we take a square mile, and line it on all four sides with lots that are just over a half acre, we come up with 116 lots per square mile. If we multiply that by the average household size in the US of 2.58 persons per household, we get about 300 people per square mile in the countryside. If you multiply that by the 24,945 square miles covered by our region, you get 7,483,500 people. If you remove some to consider that a considerable portion of our region is the Chesapeake Bay and that some of those 24,945 square miles are already taken up by towns and, therefore, the Lace of Country Streets wouldn’t apply, it basically adds up to the rest of the people we were looking for.

So what we end up with is a pretty even population distribution across the entire region with a bit more concentrated in the many small towns and a lot more concentrated in the few big cities. but is this even distribution good for people or for the environment? I take issue with part of Alexander’s rationale for this pattern:

Two different necessities govern the distribution of population in a region. On the one hand, people are drawn to cities: they are drawn by the growth of civilization, jobs, education, economic growth, information. On the other hand, the region as a social and ecological whole will not be properly maintained unless the people of the region are fairly well spread out across it, living in many different kinds of settlements – farms, villages, towns, and cities – with each settlement taking care of the land around it. Industrial society has so far been following only the first of these necessities. People leave the farms and towns and villages and pack into the cities, leaving vast parts of the region depopulated and undermaintained.

But what does it mean to “take care of” and “maintain” the countryside? It seems to me that the countryside does pretty well without us up in its business. Alexander mentions the ecology of the city and how large cities are bad ecologically, but (a) some of Alexander’s patterns that I will discuss later address that and (b) by pulling people away from the countryside and concentrating them in cities, it allows for the countryside to function as what we need it most for (a carbon sink), and allows people to take advantage of shared walls and transit systems which greatly reduce our per-capita carbon footprint. If it were me, I’d distribute the population more like this:

Click to enlarge.

Click to enlarge.

Making all the big cities even bigger and, most importantly, denser, and leaving only small villages sprinkled throughout the countryside. As long as enough people live out there to grow the food and operate the mines for everyone else, there’s no reason to have everyone flung out across the landscape. The best thing we can do for the countryside really is to leave it alone. As far as getting people access to natural environments, we’ll talk about that soon, when I take a look at Alexander’s 3rd pattern, City Country Fingers.

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About Dave Munson
This blog is about architecture, cities, and myself.

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