Land Suitability Analysis For Residential Development In Sri Lanka Based On MCDM And GIS

This study presents a Geographic Information System(GIS)based multi-criteria analysis for assessing locational suitability for residential development.It combines Multi Criteria Decision Making(MCDM)techniques with GIS based land suitability analysis model.The MCDM method,Analytic Hierarchy Process(AHP)is used in the study.The study area is the Biyagama Divisional Secretariat Division(DSD)located in Sri Lanka.This area was chosen for the study due to various factors such as locational significance,relatively short commuting times to the capital-Colombo,existence of mixed residential and industrial land use types,lower urban population density,the effect of the Kelani river flooding and low land prices.The objective of the study was to recognize multiple criteria associated with residential land suitability in this particular study area,to develop a GIS data framework for such influential criteria,to identify residentially suitable lands using the MCDM integrated GIS system,and to suggest a set of recommendations for residential land development and research.Two types of data were collected in this research;primary data which included data gathered from a questionnaire survey and through expert opinion,and secondary data which are spatial and attribute data acquired to build the geodatabase in Arc Map 10.2software.Among many,six criteria were chosen as most influential in residential land suitability in this study area through expert opinion and questionnaire survey.Population density,road proximity,land use type,land value,town center proximity,and flood risk are those criteria.Through the data collected from the questionnaire survey’s pairwise comparisons for the above six criteria,a pairwise matrix and a normalized pairwise matrix were created using AHP techniques & geometric mean.This became helpful in calculating the main criterion weights,with flood risk being the most important criteria followed by land value with the highest and second highest weight values,respectively.The pairwise matrix was checked for response accuracy through a Consistency Ratio(CR)check and the calculated CR value was 0.0074 and it is smaller than the acceptable CR value of 0.1,as defined by Saaty.Hence it was considered consistent and went forward with the analysis.Using the spatial data layers collected,Arc GIS geodatabase was created for the six chosen factors.Some data layers were acquired from respectable Sri Lankan authorities and some were created by the researcher,combining spatial and attribute data collected.All data layers were converted to raster format and four subclasses were defined for each criterion.Using the questionnaire survey data,these defined subclasses were ranked and weighted.Then all raster maps were reclassified into these four classes with their respective assigned weights.Model Builder in Arc Map is used to run the analysis.Reclassified maps were run through a weighted overlay process to find the final composite suitability map.The final results showcased a map with four suitability classes with class 4 being the highly suitable and 0 being the not suitable class.In over 13 division areas,the majority of the extent was identified as highly suitable.Built-up areas,river banks and low-altitude lands were quite rightly identified as not suitable.These results of the study can be used to support planning efforts in underdeveloped areas in the Biyagama DSD.Relevant planning authorities also can refer to these results in selecting lands for housing development projects.