Density

Maps 2014 (19) Empty Europe
teselas pobladas EURO 2006

Populated celles. They have not been aggregated, so the overall black color corresponds mostly to the adjacent limits.

This is not, as I often do, a map that has been done by someone else, but rather raw data from Eurostat that I have represented. Some months ago I commented on a project concerning a population grid, 1 km wide, covering the whole of Europe, as to give a better vision on some issues, as population, whose rendering following administrative basis was far from good.

So, there I went to the Eurostat specific site ((http://epp.eurostat.ec.europa.eu/portal/page/portal/gisco_Geographical_information_maps/popups/references/population_distribution_demography) to download the GEOSTAT 1 km2 population grid, with associated 2006 population data. The density map is somehow known as we know the main cities and axis, but what is less known is the map of the void spots (in fact, Eurostat does not produce a polygon for those 1 sq m cells without residents). As often for European data, there are countries out of the Union (Switzerland, Norway, Iceland) that are represented, while others (Cyprus) are not there).

The available cells (the populated ones, almost 2 million) help get the voids by exclusion; at first glance you can see substantial void areas in Spain, the Alps, the Charpatians, parts of Greece and the Scottish and Scandinavian mountains.

But it is far more interesting to better portray the empty areas.

Green cells have no population. So much more void...

Green cells have no population. So much more void… but there is a need to cultivate and to produce the environmental services needed by the population.

Back of the envelope calculations (2) 32 households

32vivs-1

In 2012 each Spaniard spent on average 1.585 euros in food and non-alcoholic beverages, according to INE’s statistics on household expenditure. The average expenditure by household was 4.060 euros. So each week there was an average expenditure of 78 euros. These figures are a national average, taking into account central Madrid and the last rural hamlet, so computing a wide array of costs and expenditure capacity.
According to data from the realtor idealista.com, there is in Madrid a certain amount of retail spaces to be let at about 5€/sq m, usually in peripheral areas with low- middle-income families.
Taking as a criteria that the rent would be equivalent to 5% of sales, a 100 sq m space with a 5€/sq m monthly rent should sell 10.000 € each month; i.e., it should have 32 households spending their whole food budget each week if you want to be in the food segment.
Those figures must be fine-tuned taking into account location, client conditions, retail strategy or shop format. But they are clearly indicating why retail concentrates, and why it would not be realistic to expect large shop numbers in low density urban areas (but for big-box retail). So density matters a lot.

The full picture: density helps

The full picture: density helps

Maps 2014 (6) A persons map

maps 2014-6-census map america

The Weldon Cooper Center for Public Service, at Virginia University, has published a map showing the results of the 2010 US Census at the census block level. For each person in the country there is a dot: blue for Caucasians, green for people of African ancestry, red for Asians, orange for Hispanics, and brown for others. As your screen has no resolution enough to see the distinct dots, you will see hues that reflect the mixed color according to the proportion. So you can see population density as well as the geography of segregation.

Quite an interesting trip to enter this map. In some countries in which race data is not used for census (according to a legally established will to avoid discrimination), as in France, such a map can not be drawn (as the data does not exist in a systematic way), despite the fact that it could be of some use. This does not mean you have no data on poverty, but rather that you are portraying effects, not what you think may be the cause.

Mexico City (1) No eyes on the street at megacity core?

Which is the biggest city in the world? Hard to tell; take a bunch of five geographers from different countries in front of the same territory, and chances are you will get five different limits maps for that same area. It is hard to know whether the largest city in the world is Tokyo, or Mexico, or Delhi, as you should begin by defining precisely what being a city means at such scales (UN criteria can be questioned). What seems clear is that the biggest city (in any sense) of the Spanish-speaking world is Mexico. As in other cases, again a city I have never set a foot on (so I thank any comment, especially from my Mexican readers). The country can be seen from Spain with mixed sensations: curiosity for such a culturally complex country, a degree of caution regarding an image of violence and inequality, astonishment due to the dimension of the problems, and interest for a society that seems to be evolving. This stroll will use as a guide a set of city block files from INEGI that have associated data and have led me to ask some questions.

Metropolitan area of the Mexico Valley

Mexico Valley metro area’s blocks

The first image shows most of the blocks of what can be defined as the (more or less) continuous city. Blue hues correspond to blocks in Mexico State, red being for those in the Federal District; color intensity increases with the population of each block. The graphical scale illustrates the spatial magnitudes of this, for a city that in 2010 had some 20 million residents according to INEGI.

Total population by city block in Mexico's urban core

Total population by city block in Mexico’s urban core

The second image shows the symbolic city core; blue crosses are separated 500 m in each direction. Here are the Zócalo square (1), the Cathedral (2), the Torre Latinoamericana (3), the Palacio de las Bellas Artes (4) and the Paseo de la Reforma (5). Red hues are proportional to the population of each block, written on each of them. It is surprising to see that this area, with 220 blocks, has a population of just 68.000 on 4,5 sq km, a density (150 per hectare) which seems rather reduced for an urban core; the figure seems justified by retail and office uses, but not due to an increasingly older population, as in other urban cores (see the following images). The midterm impact of recent measures as the conversion to a pedestrian configuration of calle Madero, which is positive for mobility and security, should be positive, but remains to be verified in terms of local demography.

Judging from these references, and taking Jane Jacobs as a reference, the question is whether there are any eyes at night over the core of the megacity…

Population up to 14 by block

Population up to 14 by block

Population over 60 by block

Population over 60 by block

Under the rug (5) As the rug roars

Male is the capital of the Maldives. Slightly over 100.000 people on a very restricted space in the middle of the Indian ocean. A substantial part of the city has been recently built, and land reclamation is still active, as the images from http://landsatlook.usgs.gov/ show. A race between urban and demographic growth on one side, and sea level rise on the other side due to climate change.

But this is not the Netherlands, or New Orleans. There is no hinterland to reach in case of flood. And anything thrown to the sea could be nearby, and brought back by the tide.

Barrio de Salamanca (6) Density

salam-colonLet’s go back to the inception. The project for the urban extension of Madrid was prepared between 1857 and 1860 by Carlos María de Castro, including the current Barrio de Salamanca, and set to take Madrid from 270.000 to 450.000 residents in a century. Altough people still talk of the Castro Plan (planners, as there has been not an extended knowledge among lay people as in Barcelona), it has become, as well as in Barcelona, quite different from the initial plan, even if the structure and the idea of a grid is clearly there.

The Castro Plan (Anteproyecto de Ensanche, enacted july 19, 1860) established a maximal height of 3 levels (ground floor+2) with a maximal ground ocupation of 50% of the lot area. But in 1864 the Government increases height from 3 to 4, reducing the space for courtyards and gardens to 30% in lots over 10.000 sqm, and to 20% in lots with smaller areas, allowing private streets to be counted as such. 1867 is the year in which the old city bylaws come to be applied to the extension area, rising so height to five levels plus penthouses. Castro is substituted as chief officier for the urban extension of Madrid in 1868, and in 1873 municipal bylaws reduce street width, supress gardens on private spaces, and legalize any previous building. And as in any administrative bad joke, the Definitive Extension Plan (the 1860 plan was deemed to be a draft) is aproved in 1898, when a substantial part of the extension was already built.

The Castro Plan aimed to get to a ratio of 50,98 sq m of built area per resident for the whole of the urban extension, improving the then current ratio of 28,68 in the old city. Nowadays, and taking only the Barrio de Salamanca on the part of the same name ward that is west of calle Francisco Silvela, there are 83.000 residents and 282 persons per hectare (residents only). Cadastral data say there are slightly over 6 million sq m of built area for housing, so there are some 73 sq m of housing per resident. Way ahead of what Castro aimed for on average, altough this figure masks strong variations…

 

Biblio (66) Subdividing individual homes in central Île-de-France

biblio 66-division pavillonaire ile de france

 

A new study directed by the Institut d’Amenagement et d’Urbanisme de la Région Île-de-France (the parisian regional planning agency) shows that in this region:

a) In most of the municipalities having experienced urban density increases between 1999 and 2008 there was no increase in land area for housing.

b) 25% of the new home units appeared between 2001 and 2011 came from pre-existing buildings refurbishment.

This has not happened in a uniform way across the regional space, with areas in which high real estate prices have driven a reduction in the number of homes (quite few and of small size), while others (most) have gone the opposite way.

Up until now the impact of these dynamics on individual home urban tissues was not well known. Some 2.000 homes are produced each year by subdividing some 770 individual homes, mainly in low- middle income areas with reasonable services and public transportation. Usually ownership transforms in rent units, to which young families go.

This text addresses something which is, in fact, a historical constant: as cities grow, their tissues usually densify, and now a time has come to see how a regulated urbanism copes with that on a massive scale.

Some can see here a victory for public transportation, as this concentrates growth in well served areas; I think more data is needed to see which part of residential choice is induced by that, but no doubt this is also relevant in a congested area as metro Paris.

Biblio (63) Square cells…

biblio 63-1

This biblio post is about a powerpoint presentation by Jean Luc Lipatz (from the French National Statistics Office) on the new geodata publishing method that is being used for census and other datasets. The whole of Europe (the system is being deployed by the concerned countries) is covered by a set of pixels, each of which has the data on what is in; a way more precise method to geographically show what exists, when compared to previous methods based on atributing data to each administrative entity.

Biblio63-2

On snails and shells

Which are the figures that can show how good a given urban structure is ? it is often heard that urban density is a relevant figure, and it is a reasonable assessment; the floor-area ratio (how many sq m or sq ft you get to stack over a given area) gives an illustrative figure, that can be easily compared between different contexts. But to agree on the thresholds between high, medium and low density is more difficult, as this depends on culture; as etiologists show that the distance a person accepts as a reasonable intimacy area when surrounded by a set of persons varies with culture (in many sparsely populated regions this value is somewhat high, while in overpopulated cities it is rather small, otherwise the underground would not be used…), the threshold for high density can vary even inside a single country. For instance, in Spain some regional planning laws limit the FAR to 1 (ratio of built floor surface to the development zone area), but some as the Basque Country (in which land uses compete for scarce valley plains) or Galicia (with a tradition of dense urban cores) allow much higher values. Even from an environmental point of view, density must be defined taking into account the carrying capacity of the site.

A second figure is also important: the occupation level of the already urbanized and serviced land. An airline whose occupation ratio were to be 50% of the potential tickets would strive to get profits, and the same happens to a city: maintaining the streets has a cost, usually covered by fiscal income, so no residents means a complex situation, as Detroit painfully reminds.

So density is about how many snails you have in a shell (well, usually one…), and occupation level tells how easily the bug can move the shell…

London and population density

Lond-denspop

Is London a dense city? Well, related to what?.  The map represents the population density (persons per hectare, UK Census 2011); it is striking to see that the scenic central London, seen by tourists, is a sort of void. The red lines are tube lines, and the names are those of some stations.