Magnitude and frequency of paleofloods and historical floods in the Arava basin, Negev Desert, Israel

The paleohydrological records of 14 drainage basins in the hyperarid Negev Desert, all draining to the Arava Valley, are inferred from slackwater deposits and other paleostage indicators at 19 study sites. The paleoflood records of 6 drainage basins include 20-30 floods with magnitudes that are at least 2-3 times larger than the maximal measured peak discharges. The temporal distribution of the palefloods indicates alternations between periods of different frequencies of flooding, representing fluctuations in the hydroclimatological regime. These paleoflood records, augmented by the short and partial systematic and historical records of the last decade, were reanalyzed for flood frequency. The records of the other 8 drainage basins are partial and include up to 9 paleofloods each. The reconstructed peak discharge of the largest flood in each drainage basin serves as a data point for a maximal peak discharge envelope curve established for the Negev. Using empirical correlations between flood peaks and volume, the volumes of the paleofloods were estimated. The flood volumes serve as major input data for the estimation of transmission losses and recharge to the Arava Aquifer.