Israel
Israel
The Kuiseb River floods attenuate along the >100 km bedrock canyon channel, losing by transmission large volumes into a relatively wide (200-400 m) sandy braided alluvial downstream channel (~100 km) and reached the ocean only ~10 times since 1890. Slackwater flood deposition was found at 29 sites along ~120 km of the canyons of the Kuiseb River and its main tributary, the Gaub River and there were documented, dated (14C, OSL), and modeled five sites/reaches. A sequence of 13 flood units since early 20th century and 27 flood units since about >1000 years ago have been described. Step-backwater calculations using HEC-RAS indicate that floods of ~850 m3sec-1 deposited these two sequences. The largest Kuiseb River flood upstream of the Gaub-Kuiseb confluence was estimated in ~1350 m3s-1 based on a line of rotten tree logs on top of thin flood deposited (>5 ka) overlying a much older terrace. The frequency of these large floods is then used in determining the long-term frequency of recharging events along the entire river.
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