Challenges of relief modeling in flat areas: a case study in the Amazon coast floodplains

Abstract

This study aimed to evaluate the performance of eight digital elevation models (DEMs), i.e., one digital terrain model (DTM) obtained from airborne P-band radar (BCDCA DTM), one digital surface model (DSM) obtained from airborne X-band radar (BCDCA DSM) and six DSMs from orbital sensors (AW3D30, ASTER GDEM, Copernicus DEM, NASADEM, SRTM, Topodata), for the morphological characterization of the floodplains of Amapá (Brazil). All DEMs were resampled to the same mesh size and compared by visual and statistical analysis in terms of elevation and slope. The comparison demonstrated that the DTM obtained from P-band radar images was the most consistent one in representing the landforms, as it is less sensitive to vegetation. The behavior of the automated hydrographic network extraction was also analyzed, showing that even the DTM was not able to detect drainage lines across flat landscapes with centimeter elevation variations. As the comparisons were made with a common 30 m grid, the conclusions are limited to this scale and the effect of a change of scale is discussed. In view of the difficulty of automatically extracting the network in a plain, the possibility to reduce the modelling to a 2D approach, based on external hydrographic data, is also discussed.