Abstract
Abstract. The contribution highlights the use of Landsat spectral-temporal metrics (STMs) for the detection of surface anomalies that are potentially related to buried near-surface paleogeomorphological deposits in the Nile Delta (Egypt), in particular for a buried river branch close to Buto. The processing was completed in the Google Earth Engine (GEE) for the entire Nile Delta and for selected seasons of the year (summer/winter) using Landsat data from 1985 to 2019. We derived the STMs of the tasseled cap transformation (TC), the Normalized Difference Wetness Index (NDWI), and the Normalized Difference Vegetation Index (NDVI). These features were compared to historical topographic maps of the Survey of Egypt, CORONA imagery, the digital elevation model of the TanDEM-X mission, and modern high-resolution satellite imagery. The results suggest that the extent of channels is best revealed when differencing the median NDWI between summer (July/August) and winter (January/February) seasons (ΔNDWI). The observed difference is likely due to lower soil/plant moisture during summer, which is potentially caused by coarser-grained deposits and the morphology of the former levee. Similar anomalies were found in the immediate surroundings of several Pleistocene sand hills (“geziras”) and settlement mounds (“tells”) of the eastern delta, which allowed some mapping of the potential near-surface continuation. Such anomalies were not observed for the surroundings of tells of the western Nile Delta. Additional linear and meandering ΔNDWI anomalies were found in the eastern Nile Delta in the immediate surroundings of the ancient site of Bubastis (Tell Basta), as well as several kilometers north of Zagazig. These anomalies might indicate former courses of Nile river branches. However, the ΔNDWI does not provide an unambiguous delineation.
Highlights
The reconstruction of the paleo-topography and paleohydrography of the Nile Delta plays a central role in landscape-focused archeological investigations
The georeferenced datasets were integrated into a geographic information system (GIS) geodatabase along with the TanDEM-X digital elevation models (DEMs) and the features derived from the Landsat time series
The branch is located several kilometers north of Buto and appears visibly in the TanDEM-X DEM as its levee is slightly higher than the floodplain (Fig. 4)
Summary
The reconstruction of the paleo-topography and paleohydrography of the Nile Delta plays a central role in landscape-focused archeological investigations. The earliest textual sources that allow, to a certain degree, the reconstruction of the branches of the Nile mainly date from the 5th century BCE to the 4th century CE and come from various Greek and Roman authors (including Herodotus, Diodorus, Strabo, and Ptolemy). These sources named and described the estuaries of the Nile and the landscape/riverscape of the delta in more or less detail; they generally do not allow clear localization in today’s topographic context. Most records indicate seven main branches of the Nile, which were either named after the cities at their mouths or after an important city located on the respective arm (Bietak, 1975; Ginau et al, 2019)
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