Quality assessment of open access Digital Terrain Models to estimate topographic attributes relevant to soil vertic properties prediction. A case study of Entre Rios province (Argentina)

GRACIELA METTERNICHT; HECTOR DEL VALLE; FERNANDO TENTOR; LISANDRA P. ZAMBONI; PABLO ACEÑOLAZA

Viena

Otro; EGU General Assambly 2022; 2022

European Geoscience Union

Digital terrain models (DTM) allow deriving topographic attributes that help predict soil propertieswithin a landscape. A variety of DTMs, digital elevation models (DEMs), and digital surface models(DSM) derived from Earth Observation (EO) data are freely accessible via Internet for downloadand use: MERIT-DEM, SRTM v3 (SRTM Plus), GDEM v3 (ASTGTM), AW3D30 v3, Copernicus GLO-30,NASADEM HGT v1, SRTMGL1 up-sampled (ASF DAAC) and MDE-Ar v2. However, information ontheir accuracy to represent terrain surfaces (particularly topographic attributes) can vary accordingto regions and geographies, which can impact soil cartography accuracy at sub-regional andcatchment levels. This research evaluates the accuracy of the models mentioned above forestimating topographic attributes relevant to the cartography of soil vertic properties in thenorthern part of the Entre Ríos province, Argentina. To this end, east-west and north-southtransects were used to collect 126 evenly distributed ground control points. The root meansquared error (RMSE) and symmetric mean absolute percentage error (sMAPE) served as the basisfor comparing the performance of the terrain models. The sMAPE provides a percentage (orrelative) error, facilitating a comparison of the accuracy with which each elevation value ispredicted (in addition to the average error expressed by the RMSE value).The results show that out of the 8 models compared, the Copernicus GLO-30 offers the highestaccuracy (RMSE=1.36; sMAPE=1.5%) for representing terrain surface features in the province ofEntre Rios, whereas the highest RMSE (7.79) and sMAPE (11.2%) corresponded to the ASTGTM v3.The paper describes a simplified approach for extracting a digital terrain model (DTM) from thedigital elevation information provided in the Copernicus GLO-30. Grid-spline interpolation andmultilevel b-spline interpolation (from SAGA open GIS software) were applied to remove naturaland built features. The output DTM was used to calculate plan and profile curvature index, multiscale topographic position index (TPI), multiresolution index of valley bottom flatness (MrVBF),terrain ruggedness index (TRI), and topographic wetness index (TWI) that are important inmodelling relationships between geomorphology, vertic soils, and surface hydrology in landscapescharacterized by catenary sequences of Mollisols-Alfisols-Vertisols. A higher TRI was associated toincreased local relief heterogeneity. Higher values of the MrVBF relate to broad flat valley bottomsand more extensive alluvial zones often confined between the slightly rolling and undulatingplains, and peneplain landscapes. Lastly, the TWI was used to map potential areas for surfacewater accumulation that field verifications showed as corresponding with the location of verticsoils. Integrating DTM-derived topographic attributes with other ancillary data enabled mapping thespatial distribution of soil vertic properties over the study area and associating their occurrence tospecific landscape zones (ie. close to drainage networks). The approach and findings are relevantfor showing where and how the landscapes of the Entre Rios province are affected by a combinedimpact of human activities (intensive agriculture) and a hydrographic network that boosts theprocesses of soil erosion and contaminant transport.