Spatial sensitivity analysis of multi-criteria weights in GIS-based land suitability evaluation Y. Chen a, b, * , J. Yu a, c, d , S. Khan a, e a CSIRO Land and Water, GPO Box 1666, Canberra ACT 2601, Australia b Cooperative Research Centre for Irrigation Futures, Australia c Department of Geography, Shanghai Normal University, Shanghai 200062, PR China d Key Laboratory of Geographic Information Science (Ministry of Education), East China Normal University, Shanghai 200062, PR China e UNESCO Division of Water Sciences, 1, rue Miollis, 75732 Paris Cedex 15, France article info Article history: Received 11 February 2010 Received in revised form 28 May 2010 Accepted 1 June 2010 Available online 22 June 2010 Keywords: Sensitivity Multi-criteria decision-making AHP ArcGIS abstract With growing interest in extending GIS to support multi-criteria decision-making (MCDM) methods, enhancing GIS-based MCDM with sensitivity analysis (SA) procedures is crucial to understand the model behavior and its limitations. This paper presents a novel approach of examining multi-criteria weight sensitivity of a GIS-based MCDM model. It explores the dependency of model output on the weights of input parameters, identifying criteria that are especially sensitive to weight changes and to show the impacts of changing criteria weights on the model outcomes in spatial dimension. A methodology was developed to perform simulations where the weights associated with all criteria used for suitability modelling were varied one-at-a-time (OAT) to investigate their relative impacts on the final evaluation results. A tool which incorporates the OAT method with the Analytical Hierarchy Process (AHP) within the ArcGIS environment was implemented. It permits a range of user defined simulations to be per- formed to quantitatively evaluate model dynamic changes, measures the stability of results with respect to the variation of different parameter weights, and displays spatial change dynamics. A case study of irrigated cropland suitability assessment addressing the application of the new GIS-based AHP-SA tool is described. It demonstrates that the tool is spatial, simple and flexible. Crown Copyright Ó 2010 Published by Elsevier Ltd. All rights reserved. 1. Introduction Multi-criteria decision making (MCDM) is primarily con- cerned with how to combine the information from several criteria to form a single index of evaluation. GIS are best suited for handling a wide range of criteria data at multi-spatial, multi-temporal and multi-scale from different sources for a time-efficient and cost-effective analysis. Therefore, there is growing interest in incorporating GIS capability with MCDM processes. Spatial MCDM has also become one of the most useful methods for landuse and environmental planning, as well as water and agricultural management (Davidson et al., 1994; Ahamed et al., 2000; Joerin et al., 2001; Ceballos-Silva and López-Blanco, 2003; Sicat et al., 2005; Chen et al., 2007). As a result, the request for GIS models and tools supporting collaborative decisions has increased over the last decade (Kollias and Kalivas, 1998; Karnatak et al., 2007; Reshmidevi et al., 2009; Chen et al., 2009). GIS-based MCDM involves a set of geographically defined basic units (e.g. polygons in vectors, or cells in rasters), and a set of evaluation criteria represented as map layers or attributes. Based on a particular ranking schema, it ultimately informs a spatially complex decision process by deriving a utility of these spatial entities through overlaying the criterion maps according to the attri- bute values and decision maker’ s preferences using a set of weights. Therefore, besides criteria selection, criteria weights severely impact the results of the MCDM. Using Analytical Hierarchy Process (AHP) is one of the most popular methods to obtain criteria weights in MCDM (Saaty, 1977, 1980; Saaty and Vargas, 1991; Wu, 1998; Ohta et al., 2007). The AHP has been employed in the GIS-based MCDM (Carver, 1991; Malczewski, 1999a, 1999b, 2004; Makropoulos et al., 2003; Marinoni, 2004; Marinoni et al., 2009). It calculates the needed weights associated with criterion map layers by the help of a pref- erence matrix where all identified relevant criteria are compared * Corresponding author. CSIRO Land and Water, GPO Box 1666, Canberra ACT 2601, Australia. E-mail address: yun.chen@csiro.au (Y. Chen). Contents lists available at ScienceDirect Environmental Modelling & Software journal homepage: www.elsevier.com/locate/envsoft 1364-8152/$ e see front matter Crown Copyright Ó 2010 Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.envsoft.2010.06.001 Environmental Modelling & Software 25 (2010) 1582e1591