Strategic spatial planning effectiveness in land change. Case of Lyon urban region

Résumé En

Spatial planning is one of the main drivers of land change in metropolitan areas. In these highly constrained areas, the strategic vision of territorial development must be supported by local actors within a process sufficiently effective to lead development in relation to a trajectory guided by other drivers such as economic and biophysical factors. But, what planning effectiveness threshold is necessary to make spatial planning breaks with the trend trajectory of land change? By "planning effectiveness" we mean the degree to which the envisioned development contained in the strategic plan is implemented by local actors through conventional planning processes. We developed several scenarios with the CLUMondo land-change model to assess the effects of different levels of planning effectiveness. In theses scenarios, we oppose drivers that have guided development over the past decade with the vision contained in the stractegic plan which guides development for next decades. These scenarios have been applied to Lyon urban region (France) and its strategic plan called SCOT 2030. The SCOT, Schema de Coherence Territorial, is a plan that describes the ambitions of the urban region on various themes such as demography, employment and environmental protection. These ambitions are presented as quantified objectives (maintaining a percentage of natural and agricultural areas, for example) and as means and rules to be followed to achieve these objectives (increasing densification, protecting natural areas, etc.). We distinguish between the effectiveness of an urban region in pursuing nature protection objectives and the effectiveness in managing urban sprawl, two pillars of the Lyon metropolitan area's strategic vision. Although the vision is not at a strong break with the past trend, this case study shows divergences in the trajectory at several locations. Preliminary results suggest that there is no fixed threshold above which effectiveness systematically diverges from the past trajectory and local particularities must be consider in determining this threshold.