An application of data mining for the determination of flooded areas was published in the Journal Geodetski vestnik (no. 54/2010-4). This paper analyses the usefulness of these results for further analyses of hydraulic parameters. The velocity and discharges were computed for six locations. The study showed that the flooded areas determined by satellite images can be used for further analyses. Nevertheless, other layers have to be sufficiently precise, especially the digital terrain model (DTM). DTM 12.5 was used. The study showed that DTM 12.5 is not precise enough. The observed area is very rough and the hydraulic parameters (cross sectional area of flow, wetted perimeter, hydraulic radius, river-bottom slope, flow velocity, discharge) cannot be detected with sufficient precision. Consequently the calculated hydraulic radiuses, velocities and discharges are out of expectations. In the first part of the article, some basic information about remote sensing and its techniques is presented. Some practical examples of their usage (especially satellite images) for the observation of natural disasters are also given.