Changed precipitation patterns and the need for a novel approach to building plot planning: The lessons learnt in the sub-alpine climate zone of Slovenia

The events related to climate change are challenging the Slovenian urban planning more and more. One of them are the floods in urbanized areas that call for a radically new approaches to how the cities' built structure is organised and managed. The continental (and largest) part of Slovenia has a sub-alpine climate which has been traditionally characterized by a moderate precipitation throughout the year. This is now being changed as the larger amounts of water fall on the ground in a shorter period of time. As the current urban structure is not shaped in accordance with these new circumstances, parts of the cities are getting flooded more often. Some mitigation measures have been implemented, however to address the issue comprehensively new urban planning approaches are needed too. The paper will present one of the tools that has been developed by the Urban Planning Institute of the Republic of Slovenia and partners within the endeavors of the national Ministry of Spatial Planning to reform the urban planning system to better reflect the changes posed by the climate change. It is related to the urban design criteria for building plots planning. In order to allow the rainfall to penetrate into the soil as soon as the precipitation reaches the ground, new measures in organisation of the building plots will be provided. The current system that defines the percentage of the built up area within the plot and does not take into account the paved open spaces (which do not allow the water to penetrate into the grounds) will be supplemented by the new measures based on the ability of the plots to allow the penetration of the water. The paper will firstly present the current system of building plots regulation within the Slovenian planning system. It will then report the results of the extensive analyses that focused on the existing characteristics of building plots for different building typologies across the country (housing, production, trade, central activities) with the aim to map the state of the art in terms of the potential of the existing building plots to allow the water to flow into the grounds. The third part will explain the methodological framework for the innovative approach to the building plots regulation. The last part will present the newly proposed approach and relate it to other urban design tools that need to support the implementation in practice. The concluding section will relate the lessons learnt on Slovenian case to the similar situations elsewhere and stress the responsibilities that the urban planning and design have in providing future urban environments that will ensure the environmentally just living conditions for all.