Tuesday, November 10, 2009

Size Does Matter, or Not

An interesting article in Planetizen called "Beloved and Abandoned: A Platting Named Portland" investigates one of the unique, frustrating and beloved quirks of Portland. This is, our slicework of 200 foot square blocks... making for a lot of roads, and development of tiny blocks. It's our burden to bear. The article is a fascinating ride - so check it out.

:: all images via Planetizen

The authors discuss the 'Hippodamian' grid, which is an interesting way of saying square, and relate it to current urban design theory and practice. "Current planning literature brims with references to "the grid" in juxtaposition with curvilinear and dendrite conventional suburban layouts. The "grid" as a network concept has been widely accepted and is now regarded as a superior geometry for laying out greenfield and infill sites."

There is also the reference to the success of Portland directly related to these small blocks, which I'd disagree with (as the authors soon do). I'd say Portland succeeds in spite of this phenomenon, and the issues pervade - as is shown with a reference to successful urban grids, mostly those of the non-square ilk. "Urbanists and romanticists have expressed equally strong sentiments about Paris, London, Barcelona, Curitiba, Amsterdam and Venice. Of the six, only Barcelona adopted the Hippodamian grid in 1859 for its vast expansion, and Venice, without a classic grid, is the preeminent pedestrian haven, yet neither city matches the urbanist’s praise for Portland. Whatever the mix of reasons, Portland dominates the American planners' imagination feelings and talk. Disentangling this intangible realm can be an elusive goal; grounds and figures on the other hand may produce tangible results."

A grid alone is not the recipe for success, and in practice there are few pure iterations of the grid, with zigs, zags, curvy spots, the axial geometry of Ladds addition, and many other quirks. As a fan of the grid for wayfinding and layout, there's something to be said for the rigorous adherance to the formality, which much theory has been laid out in curvy, suburban blah. Some support of the grid: "The degree of connectivity of the street network could count as another practical reason. 'Network', by definition, is a set of linked components, whether a spider-net, a fishnet, or the Internet - all networks connect. What distinguishes them is the manner, geometry and frequency of connection: leaf, tree, blood vessels, telephone and web networks are dendrite, hierarchical (fractal) but fishnets are not. Portland’s is a dense fishnet with nodes at every 200 feet, which produce 360 intersections per square mile -- the highest ratio in America, and 3 to 5 times higher than current developments. For example, older and newer areas in Toronto, typical of most cities, range from 72 to 119 intersections per square mile in suburbs and 163 to 190 in older areas with a grid. As connectivity rose in importance as a planning principle, Portland’s grid emerges as a supreme example.

Coupled with connectivity, its rectilinear geometry is indisputably more advantageous for navigation on foot, car or bike than any alternatives. Visitors often feel lost and disoriented in medieval towns and in contemporary suburbs and this feeling leads to anxiety and even fear and a sense that all is not well."

The grid is rightly stated as derived by speculators for maximum corner lots - not in the grand plan of some more model communities. The fact is, again, that the grid can improve or degrade the urban environment, as the authors mention, but success is not inherently depending on that as the only criteria. "Evidently, Portland’s founders either understood little about infrastructure costs or judged them irrelevant; a judgment that no planner, developer or municipality today would take at face value. When economic efficiency matters, Portland’s grid fails the grade."

In a theoretical sense only. There's comments from Sitte and Duany on the lack of art in the grid... but really is urban planning about art? Is curvy and artistic more successful in an urban context? I doubt it. Anyway, the fact that our grid, much like the national grid system, is overlaid on a extant topography in somewhat irresponsible ways have led to issues with erasure and negative impact on natural hydrologic patterns, which only bend when topography and streams are too steep or significant to pipe, grade, and cover over. Also, the sheer amount of street paving is significant, as our small blocks lead to significantly more stormwater impacts. This however, has been the genesis for innovative strategies such as green streets to combat this - sort of making a silk purse out of a bad grid.

While it may be easy to ignore progress in combating our bad grid, it's again a pointless thought exercise (these adaptions in the following paragraph are the lifeblood of modern urbanism, as we can't recreate what has already been created). Thus, it's interesting to think of ways of refuting the present by showing how the past is flawed:
"The ordinary impression on the ground that the Portland grid 'works' in contemporary traffic conditions is casually taken as a sign of suitability. This view obscures an entire century of engineered physical, mechanical and management adaptations which are overlaid on the 1866 platting. Remove these (in a thought experiment) and imagine the outcome. Clearly, an ill-suited geometry is made to work with interventions such as dividing lines, medians, traffic signs, traffic lights, directional signs, bollards, street widening, one-ways, traffic circles or roundabouts and many others."

I think that's called adapting to change, but then again, it's a thought experiment, so fun nonetheless. As the authors conclude:
"For reasons of land efficiency, infrastructure cost, municipal expenses, rainwater management, traffic safety and flow, and the demand for increased pedestrian share of public space, the praised, pure Portland platting will likely not find new followers. Portland will remain a adored and beloved by urbanists, but her Hippodamian grid layout seems destined for the archives, abandoned as a good idea of a byegone era. This transcendence leaves urbanists, who seek to regenerate a contemporary urban pattern that is as pure, complete and systematic, looking for alternatives: ones which excite the same first blush of adoration and delight and lead to a deep abiding love, but also hold up to intense scrutiny of their economic, social and environmental performance."

I agree with the main tenets of their thesis (and it's a great notion and read) and frankly think the grid is a pain in the ass, but it's one of those theoretical arguments that really doesn't mean much in terms of modern urbanism, particularly in a city that plans things to death and beyond. Few if any new cities are built from scratch with no existing contextual framework - so maybe in the few new communities, a particular utopian grid system can be applied - probably modeled after the latest New Urbanist theory. It'd be interesting to imagine a re-thinking of the 'Hippodamian' grid being retrofit, as is, into something else in Portland - elongated, filled in, abstracted into a more pure and reasonable pattern, with streets removed to be open spaces, bikeways, and other green infrastructural systems. But the question is moot, a thought experiment if you will, and like it or not we are stuck with our pattern.

We deal with it, we plan around it. We love its street/building staccato chatter back and forth, with our 360 intersections per square mile, and we curse the stop sign hovering on your bike every 200 feet, waiting for that car to come zipping by take you out. It makes life exciting. But, in general it doesn't mean much, and isn't as derogatory to a high quality public realm as implied. Portland isn't to be copied for urban form, and really shouldn't be degraded for a grid system that was done without regard. We're known for for innovation and foresight in policy, transportation, stormwater management, and other factors. Many of these come from the very problems that arise from our back-assward small grids. But it works, because sometimes a grid is just a grid.