Based-GIS studies of flood area and damage evaluation have been being a research focus in GIS application fields. In this paper

a new model of flood area based on seed spread algorithm and of the damage evaluation has been proposed. Two different cases so-called “non-source flood” and “source flood” exist when determining flood area based on DEM and under the given water level condition. Non-source flood corresponds to the case with well-distributed and large-area rainfall where all the low-lying land may have a flood disaster

and in this case all the points with elevations below the given water level should be included in the flood area. The “source flood” is the case of flood (e.g. from bank burst) flushing through the nearby regions and needs to consider “circulating” condition. It is because flood may be obstructed by ring structures or high lands and thus can only covers the place where it can flow and reach. The results of the flood area calculation and damage evaluation can also be visually and dynamically provided in the forms of graph

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3D or virtual reality. The model of flood area calculation and damage evaluation proposed in this paper

adopting Microsoft VC++ 6.0 programming language and Microsoft SQL Server 7.0 DBMS platform

has been successfully applied in the “Zhejiang Provincial Water Conservancy Management System” developed for a national project