A GIS method to identify flat surfaces and restore relict fluvial long‐profiles from terrace remnants gives new clues on how large basins respond to endorheic–exorheic transitions (Duero basin, Iberian Peninsula)

• Published in: Earth surface processes and landforms 2020-03, Vol.45 (4), p.1013-1027
• Main Authors: Rodríguez‐Rodríguez, Laura, Antón, Loreto, Pallàs, Raimon, García‐Castellanos, Daniel, Jiménez‐Munt, Ivone, Pastor‐Martín, Candela
• Format: Article
• Language: English
• Subjects: Accretion; Aggradation; basin opening; Cenozoic; Climate studies; Digital Elevation Models; Duero; Endorheic basins; Escarpments; Flat surfaces; fluvial terraces; Geographical information systems; Geomorphological mapping; Geomorphology; Iberian Peninsula; Landforms; Landscape; Morphometry; Neogene; Production methods; Profiles; relict long‐profile; Rivers; strath terraces; Tectonics; Terraces
• ISSN: 0197-9337; 1096-9837
• DOI: 10.1002/esp.4795

Fluvial terraces are used as geomorphic indicators for deciphering long‐term landscape evolution. Knowing the distribution of fluvial terraces is essential for establishing former river profiles and their tectonic significance, for studying climate‐modulated processes of terrace development, or for defining fluvial network adjustments in response to sudden base‐level changes like those produced by fluvial captures. Multiple methods for automatic map production have been proposed based on the comparison of morphometric indices with those of the modern river course. Here we propose an alternative method to identify flat surfaces and scarps separating them from digital elevation models without setting comparisons with a modern river course and thus fully applicable to study flat landforms whatever their origin. Its application to the low‐relief landscape of the Cenozoic Duero basin has allowed the improvement of previous geomorphological maps and the analysis of fluvial network adjustments in response to a sudden base‐level fall after the opening of the Neogene endorheic basin towards the Atlantic Ocean. Reconstructed terrace long‐profiles suggest an initial episode of fast vertical incision followed by a period of repeated planation–aggradation–incision with the formation of 14 to 13 unpaired terrace levels. Changes observed in the pattern of terrace profiles are discussed with regard to changes in regional tectonics and base‐level variations. © 2019 John Wiley & Sons, Ltd. An analysis of digital terrain models allows a fast identification of flat surface landforms and incision scarps. Relict long‐profiles are restored using a fishnet sampling of terrace surface points from DEMs. Applied to the Cenozoic Duero basin this methodology allowed us to improve previous geomorphological maps and redefine previous schemes on terrace relative heights, providing new insights on the fluvial incision history of the river in response to the endorheic–exorheic transition of the basin.