A Methodology to Generate a DEM by Combining Topographic and Bathymetric Data in Fluvial Environments
Matias, Magda Paraíso1; Falcão, Ana Paula1; Gonçalves, Alexandre1; Alvares, Teresa2; Pestana, Rita1; Van Zeller, Emília2; Rodrigues, Victor2; Heleno, Sandra3

In hydrodynamic simulations, a digital elevation model valid for the whole study area is a requirement. The construction of this model usually implies the use of topographic and bathymetric data collected by distinct equipment and methods, at different times and acquired with a variety of spatial resolutions and accuracies. Several methodologies have been tested in order to combine both datasets involving the use of diverse spatial interpolators. In this paper we present the first results of a new methodology that combines a digital elevation model (DEM) acquired by radar for floodplain areas with cross-sections in the river bed, in order to provide the most accurate and reliable digital elevation model. The study area is a section of 70 km of the Tagus River, between Tramagal and Santarém. The Tagus River is the longest of the Iberian Peninsula and is responsible for periodical floods in one of the most important agricultural areas in Portugal. For this area a DEM is available, acquired in 2008 by radar techniques (5m of spatial resolution), accurate in the floodplain area, and 29 cross-sections acquired by eco-sounder equipment in 2012, with 3km intervals. Since data was collected in distinct epochs, in the overlapped areas differences in elevation might exist, due to the morphological dynamics of the river. In order to analyse and validate those differences, a dataset with SAR imagery, provided by ESA, was used.