Stages in the configuration of urban form in urban development planning: the emerging role of open spaces as sustainability mechanism. The case of Valladolid (Spain)

Along the last five decades and through three different stages, the urban development plans —general plans— of Valladolid, a medium-sized Spanish city, show an interesting evolution in the way of configuring the global urban form and controlling urban development that we can also find in other similar Spanish cities. In the sixties and seventies, plans proposed “autonomous” expansive schemes foreseeing a huge rate of urban growth, so they defined wide areas to be urbanised through new transport infrastructures and typical zoning mechanisms. In the eighties, after decay in urban and economic development and during the transition to democracy, the new local governments focused on the existing city and fostered a more controlled urban growth. However, plans continued to employ the same tools to manage future urban form —definition of transport infrastructures and sectors to be urbanised—, although they looked for more “controllable” forms, such as radio-concentric ones, aiming at a gradual and homogeneous implementation —compact city—. When real-estate market recovered in early nineties, this strategy revealed its weaknesses: fragmented urban fringe and tendency to a congestive model, reinforced when a new generation of expansive plans drove these schemes out of the limits they were conceived with. However, an alternative and more sustainable model had already emerged, as some new urban planning tools proposed a change of perspective: managing global urban form not through future urbanised spaces, but through open ones, generating an “empty” network able to give coherence to the whole urban structure in a metropolitan scale.