To provide a system for efficiently supporting an underground dam project or the like which is a legitimate ground water development system by integrating geographic information system technology and underground dam technology, and integrally processing data of geological condition, ground water, land use, etc, and to provide a method for creating a plan of the support system.

In the technical support system for an underground dam project, a database covering every item required for formulation of an underground dam project is created, the data required for investigation and planning necessary for the formulation of the underground dam project are selected out of the database, and land-surface data relating to the possible underground dam construction site transmitted from an artificial satellite and the data selected out of the database are combined to create the land-surface data required for investigation and planning.