Development of an Environmental Geology Data Base for Land Use Planning

Abstract

A study involving a computerized data base for land use planning at the county level required early decisions (1) in the selection of physical characteristics that best describe the land relative to planning and (2) the size of the data cell for encoding and storing this information. These aspects of the complete study, which are necessary features for all computer-based land use plans, are explored in this paper. Information related to areal distribution and engineering characteristics of earth materials, topography, surface and ground water aspects, provides the needed input data for the base. Such data when supplemented with economic, cultural, and demographic information provide the basis on which planning agencies can formulate realistic land use plans. This information is digitized for computer storage and subsequent computation to be used for decision making. The first step in determining the suitability of a piece of land involved selection of the variables, which are the physical characteristics of the land. In addition, the relative importance of each variable, in relation to a given land use, is evaluated. Next, all the subcategories of each of the variables are assigned levels of importance, called ranking. These procedures are then followed by computer processing whereby the product of level-ranking and variable weighting is computed for each data point for a specific land use. The computer then sums up these products for all the variables and assigns a numerical ranking for each data point. Maps are subsequently printed out depicting the numerical value for each point from which locations with the greatest potential for the specific land use, corresponding to the highest number, can be determined. Selection of cell size for encoding data is a primary task in data base studies for land use planning. A cell provides the dimension of the land surface on which the researcher must determine the nature of the material and supply the input for the data base. The time needed to encode data increases rapidly with decreasing cell size for the same total area and is accompanied by an attendant increase in cost. Based on statistical analysis a cell measuring 154.2 m (500 ft) on the side was found to be most suitable for land use planning at county level.