Un système d'information géoscientifique pour la ville de Sherbrooke, Québec

Abstract

Urban planners as well as civil engineers of the town of Sherbrooke, still do not yet have a geoscientific information databank (GSID) that can show, with the help of a geographic information system (GIS), unconsolidated deposits and their three-dimensional aspect (thickness, topography and stratigraphy). Therefore, the main goal of this research project consists in making a detailed geoscientific information system (GSIS) of the Sherbrooke region, covering an area of 150 km 2 approximately. The GSID is elaborated essentially from well and borehole data, geotechnical reports, cartographic data and field observations. The elaboration of the GSIS is first done by setting up a GSID on Excel , using point data from the region. This GSID is then verified and corrected before being integrated finally in the ArcView GIS. In the case of boreholes not reaching the bedrock, further corrections to the thickness of the overburden are effected with the help of data from nearby boreholes and a series of successive interpolations. With ArcView software, interpolation maps can be drawn up. Several types of maps are derived from the GSID: bedrock topography, depth of the upper limit of the water table, total thickness to the overburden, and thickness and topography of different unconsolidated formations. The interpolation method used is Kriging when possible. The computation is based on a theoretical model chosen by the analysis of semi-variogrammes. By integrating the GSID to a GIS, the various municipal authorities can use the GSIS to keep an inventory of the stratigraphy of Sherbrooke's territory and define, among other things, risk zones in accordance with constraints of town planning and building of infrastructures.