This paper examines the use of optical visible and infrared (IR) data, Synthetic Aperture Radar data (SAR), and Ground Penetrating Radar (GPR) for detection, identification and mapping of exposed and buried channels under sands in the western Negev, Israel and northern Sinai, Egypt. Field observations and shallow geophysical methods corroborated the observations. The Halutza, Agur and Shunra sand dunes are the continuation of the northern Sinai dunes. Playa-type sediments from the late Quaternary are found in upper reaches of dry river channels between the dunes of the Northwest Negev and represent a deterioration of the drainage system, caused by shifting sand dunes. A dual-polarimetric radar SIR-C image from SRL-1, having two frequencies and two polarizations, exhibits meaningful differences in reflectance between the buried and abandoned channels and their surroundings. The buried continuation of Wadi Mobra and the larger Nahal Nizzana channels, under the western Shunra sand dunes, can be observed in L-band radar data. These channels are not clearly observed either in the Landsat thematic mapper TM Visible, nor in the near-infrared (NIR) images. The radar wavelengths and polarizations that improve the contrast between the buried river beds and the surrounding sand mantle are (in descending order): L(HV), L(HH) and C(HH). However, in places where the sand mantle is very thick, or where channels cut through bedrock, the visible and near infrared data (from Landsat TM) are easier to interpret, and tend to be more useful for mapping fluvial patterns.
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Thanks are expressed to friends from Ben-Gurion University of the Negev and Tel-Aviv University for their assistance in the fieldwork. They are: Dor Gafny, Yoav Sofer, Yuval Kibel, Shachar Solar, and Ido Miran. Thanks also to those who collaborated in laboratory measurements and to Shira Amir and Roni Livnon Blaustein for administrative and cartographic assistance. The Israel Space Agency (ISA) is acknowledged for providing funding for this work, under an infrastructure grant #1368-1-98. We appreciate the comments provided by Yehudah Enzel of the Hebrew University of Jerusalem and two anonymous reviewers.
- Buried channels
- Drainage system