River cross-section extraction from the ASTER global DEM for flood modeling

An approach to generate river cross-sections from the Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model (ASTER GDEM) is discussed. The low resolution and the inadequate vertical accuracy of such global data present difficulties in differentiating features of hydraulic importance, which necessitate pre-processing of the DEMs before they are used. A vertical bias correction carried out by comparison of elevation points with a high accuracy terrain model produces a considerable improvement to the cross-sections obtained. In a situation where there are some flow/stage measurements at either end of the river reach, an optimization routine combined with a conceptual flow routing method can provide an additional tool to identify the parameters of an equivalent river section. The extracted cross-sections were used in a 1D river modeling tool HEC-RAS/GeoRAS to simulate flooding on a part of the Tisza River, Hungary. Model results are encouraging and show good potential for using the suggested method in the areas of topographic data scarcity.