HESS Hydrology and Earth System Sciences HESS Hydrol. Earth Syst. Sci. 1607-7938 Copernicus Publications Göttingen, Germany 10.5194/hess-17-1021-2013 Geomorphology-based index for detecting minimal flood stages in arid alluvial streams Shamir E. 1 Ben-Moshe L. 2 Ronen A. 3 Grodek T. 2 Enzel Y. https://orcid.org/0000-0001-8367-9255 3 Georgakakos K. P. 1 4 Morin E. https://orcid.org/0000-0001-6671-7926 2 Hydrologic Research Center, San Diego, California, USA The Hebrew University of Jerusalem, Department of Geography Mount Scopus, Jerusalem, 91905, Israel The Hebrew University of Jerusalem, The Fredy & Nadine Herrmann Institute of Earth Sciences, Givat Ram Jerusalem 91904, Israel Scripps Institution of Oceanography, University of California San Diego, La Jolla California, USA 07 03 2013 17 3 1021 1034 Copyright: © 2013 E. Shamir et al. 2013 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://hess.copernicus.org/articles/17/1021/2013/hess-17-1021-2013.html The full text article is available as a PDF file from https://hess.copernicus.org/articles/17/1021/2013/hess-17-1021-2013.pdf

Identification of a geomorphic index to represent lower thresholds for minor flows in ephemeral, alluvial streams in arid environments is an essential step as a precursor for reliable flash flood hazard estimations and establishing flood warning systems. An index, termed Alluvial wadi Flood Incipient Geomorphologic Index (AFIG), is presented. Analysis of data from an extensive field survey in the arid ephemeral streams in southern and eastern Israel was conducted to investigate the AFIG and the control over its value across the region. During the survey we identified distinguishable flow marks in the lower parts of streams' banks, such as niches, vegetation line, and change in bank material, which are indicative of low flows. The cross-sectional characteristics of the AFIG were studied in relationship with contributing drainage basin characteristics such as lithology, topography, and precipitation. Drainage area and hardness of the exposed lithology (presented as a basin-wide index) are the preferred descriptors to be used in estimating a specific AFIG in unsurveyed sites. Analyses of discharge records from seven hydrometric stations indicate that the recurrence interval of the determined AFIG is equal to or more frequent than 0.5 yr.

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