Contrasting rainfall-runoff characteristics of floods in Desert and Mediterranean basins

Abstract

Abstract. Catchment scale hydrological studies on drylands are lacking because of the scarcity of consistent data: observations are often available at the plot scale, but their relevance for the catchment scale remains unclear. A database of 24 years of stream gauge discharge and homogeneous high-resolution radar data over the eastern Mediterranean allows to describe the properties of moderate floods over catchments spanning from Desert to Mediterranean climates. Comparing two climatic regions, Desert and Mediterranean, we are able to better identify specific rainfall-runoff properties. Despite the large differences in rainfall forcing between the two regions, the resulting unit peak discharges and runoff coefficients are comparable. In Mediterranean areas rain depth and antecedent conditions are the most important properties to shape flood response. In Deserts, instead, storm core properties display a strong correlation with unit peak discharge and, to a less extent, with runoff coefficient. In this region, an inverse correlation with mean catchment annual precipitation suggests also a strong influence of local surface properties. Preliminary analyses suggest that floods in catchments with wet headwater and dry lower section are more similar to desert catchments, with a strong influence of storm core properties on runoff generation.

More Extreme Precipitation in Chinese Deserts From 1960 to 2018

“…The precipitation pattern can affect the spatial distribution of the susceptibility to desert fires (Tagestad et al, 2016). The precipitation threshold can control the generation of desert ephemeral streams (Kampf et al, 2018) and finally impact the runoff coefficient of desert catchments (Zoccatelli et al, 2018).…”

Hydrometeorological analysis and forecasting of a 3-day flash-flood-triggering desert rainstorm

“…Flash-flood conditions are frequently met in arid and semiarid regions (Nicholson, 2011;Pilgrim et al, 1988;Schick, 1988;Simmers, 2003;Tooth, 2000), as these areas are generally characterized by localized high rainfall intensities (Sharon, 1972), low precipitation interception and low infiltration rates due to sparse vegetation coverage (Danin, 1983), and exposed bedrock surfaces that are partially covered by shallow, clay-rich, undeveloped soils (Singer, 2007). Although arid and semiarid regions cover more than a third of the world's land area, knowledge of flash-flood-generating rainfall properties, hydrological response, and flood-forecasting skills in these areas is limited due to poor measurements, sparse documentation, and a relatively small number of studies (Armon et al, 2018;Nicholson, 2011;Simmers, 2003;Yang et al, 2017;Zoccatelli et al, 2019).…”

“…The former is dictated by nature, while the latter also depends on the accuracy and effectiveness of the forecasting chain. Creutin et al (2013) and Marchi et al (2010) calculated lag times for Europe under various climate regimes, and found that it increases with basin area and follows a general power-law behavior, where basins in areas smaller than 100 km 2 often had lag times of less than 1 h. Zoccatelli et al (2019) found that the mean lag time for 14 arid basins (202-1232 km 2 ) in Israel is on the order of tens of minutes to several hours.…”

“…In general, flash floods remain a poorly understood and documented process (Borga et al, 2019;Foody et al, 2004;Gaume et al, 2009;Nicholson, 2011;Wheater et al, 2007) despite their devastation potential (Borga et al, 2019;Gaume et al, 2009;Inbar, 2019;Tarolli et al, 2012;Zekai, 2008) and increasing impact (Doocy et al, 2013;Wittenberg et al, 2007), especially in arid areas (Zoccatelli et al, 2019(Zoccatelli et al, , 2020. The present work aims to increase our understanding and knowledge of desert flash floods and to test practical forecasting abilities by presenting a comprehensive study of the rainstorm of [25][26][27] Apr 2018 that hit the arid Zin basin in southern Israel (1400 km 2 ; Fig.…”