Analytical hierarchy process coupled with GIS for land management purposes ::a decision-making application

This paper discusses the practical adaptation of a land-use planning methodology in Switzerland as a result of a combined usage of Geographic Information Systems (GIS) and a multiple criteria decision analysis (MCDA) method. The two approaches were integrated in order to help land managers to incorporate the impact of two land-use laws voted by citizens in 2012 and 2013 respectively. The direct democratic system in Switzerland allows citizens to participate actively in the decision-making processes in different fields of interest. In 2012 Swiss people voted in favor of limiting the construction of second homes, this initiative had as slogan “Ending the invasive construction of second homes”. The purpose of the initiative is to protect citizens, heritage and the nature as well as the creation and maintenance of cities, habitats and liveable landscapes. According to the initiative, second homes cannot exceed 20 percent of the total community housing of a municipality. Currently this initiative is a federal law adopted by the national council and must be applied by all municipalities. Nevertheless, decision makers (DM) were not provided of an established methodology to determine and justify their choices before the citizens. Furthermore in 2013 Swiss citizens voted for another law on land-use which aims at limiting the size of the areas that will be built. According to this new rule building permit grants will be based on the foreseeable needs for the next fifteen years. In this context municipalities need to make decisions regarding two opposite objectives: How to respect environmental criteria while keeping in mind social-economic issues. Another important question arises: which are the most suitable areas that meet the new legal requirements? These most suitable areas will be freed up at the end of the process. The main goal of our research was to develop a decision support methodology to help DM to make decisions objectively while minimizing the negative impacts of these choices in the Swiss canton of Valais. For example by identifying the most suitable hectares to be freed up through the zoning process. This was done by using a mathematical psychology method called Analytical Hierarchy Process (AHP) developed by Saaty (1977) which is based on ratio scales derived from pairwise comparisons in this case of spatial criteria. We developed a participatory process where DM and stakeholders with relevant knowledge chose seven spatial criteria. The number of spatial criteria were based on Miller (1956) research which suggested “the magical number seven, plus or minus two” which implies that humans can only process a limited amount of elements in information processes. An applicable solution provided by the integration of AHP and GIS in order to choose the location to be freed up is given by the minimum distance from the theoretical ideal. Thus when the distance from the ideal decreases the criteria are scored higher on the priority scale by the DM and when the distance increases from the ideal, those criteria are scored lower (Carver, 1991). The results were analysed on a GIS with the aim of creating a map series with the visual outcomes. In the first AHP session right before winter (November 2015) DM scored the spatial criteria “distance to the snow removal plan on the roads” was ranked as the most important with a weight of 40.2 percent. In the second AHP session in spring (April 2016) with exactly the same spatial criteria and the same participants the weight of this criteria was only 8.9 percent and was ranked on the fourth place. Other major differences were found among the two AHP sessions in winter and spring. Results suggest that the timing of the decision-making process might have an impact on the preferences of spatial criteria. At the moment of the first AHP scoring process the city was deploying the snow removal plan. It appears that the relative importance of spatial criteria that are directly influenced by the weather conditions varies considerably if the scoring process is achieved in different seasons. At the end of both sessions in winter and spring respectively DM were satisfied with the two results and discussed openly about it arguing that every result represented their preferences at the moment of each workshop. Important differences were registered in the two AHP iterations so two different spatial scenarios were developed and DM decided to keep both of them. The final decision is currently discussed on a political scheme