The other urban-rural divide
Spatially, the discrepancies between urban and rural rental housing markets continue to increase. On average, vacancy rates in the five largest Swiss cities rose only marginally from 0.35 % to 0.39 % in 2017. There is still a large excess in demand in many neighbourhoods. Due to the shortage, it has hardly been possible in recent years to channel a large part of population growth into the core cities. The discrepancy between decentralised population growth and central employment growth has also led to a massive increase in the hours wasted due to congestion on the national road network. These developments make the discussion about progress in internal densification very urgent.
Small towns with challenges
One problem with densification is that the planning processes react with a considerable time lag to the increasing demand for space. Many cities anticipated growth at an early stage, acted quickly, initiated building densification projects and thus steered the strong growth upwards. These include above all the Zurich agglomeration towns of Opfikon, Wallisellen, Bülach and Wetzikon. Other towns had corresponding open spaces and absorbed the growth in the existing low-rise structure by expanding in the width. Bulle, for example, grew by 3.2 % per year between 2005 and 2015. At just under three floors, the average number of floors of new projects has not changed compared to the existing housing stock. For many small core and agglomeration towns, the question arises as to the quality of densification. They are in part strongly characterised by small urban forms with private outdoor spaces and offer hardly any public spaces and recreational areas. In this respect, the large centres offer much better starting points for structural densification.
Urban density in Basel
Correspondingly, we thus turn our attention to the city of Basel as an example. Over the past ten years, Basel has often been overshadowed by the major economic engines of Geneva and Zurich. But Basel has caught up in the wake of the financial crisis. The life science cluster is thriving and has attracted many highly skilled workers who need housing. At least since 2014, when vacancy rates in the city had fallen to a historically low level of 0.2 %, the question of good densification has also become more acute in Basel. Port and industrial areas still offer many opportunities for new uses. The Statistical Office of the Canton of Basel-Stadt is forecasting further significant population growth, particularly in the coming years. In the medium scenario, this forecast should be achievable with only 400 to 500 additional flats per year. This scenario is taken into account in the revised zoning plan - even if setbacks have occurred in individual measures such as urban fringe development in the east of the city.
Optimising densification projects using a digital investment model
Integral digital investment models offer great potential for faster identification, resilient modelling and better communication of development opportunities in urban areas. The parameterisation of existing building structures and volumes that are feasible under construction law enable a rapid analysis of potential densification options. The volume-based, usage-differentiated consideration of cost and revenue factors in the digital investment model (DIM) allows early variant diversity and targeted optimisation interventions. In the future, these developments should contribute to better computer-aided recognition of critical dependencies and to the earlier resilience of decision criteria for densification projects. We can therefore hope that together with big data, digital planning will have a positive influence on urban density.