Statistical analysis of flash flood events for designing water
harvesting systems in an extremely arid environment
A water harvesting system for research purposes has been established in
the Lisan Peninsula of the Dead Sea in the middle of the Jordan Rift
Valley, where no authorized guideline is available for designing water
harvesting systems. Rainfall and runoff, which occurs as flash floods,
are being observed at the downstream end of a gorge having a 1.12
km2 barren catchment area since September 30, 2014.
Due to the extremely arid environment, water current as the runoff from
the catchment is ephemeral, and the flash flood events can be clearly
distinguishable from each other. Thirteen flash flood events with total
runoff volume more than 100 m3 have been successfully
recorded during five rainy seasons. The duration, the total rainfall
depths at two points, the total runoff volume, the maximum runoff
discharge, and the bulk runoff coefficient of each flash flood event are
considered as the random variables to be analyzed. Correlation analysis
among the variables is conducted in terms of the classical methods of
Pearson’s correlation and Spearman’s rank correlation, revealing that
there is no straightforward relationship between rainfall and runoff.
The performance of the conventional SCS runoff curve number method is
also deficient in reproducing any rainfall-runoff relationship.
Therefore, probability distributions are fitted to the empirical
distribution of each variable. The lognormal distribution with three
parameters and the generalized extreme value distribution serve well.
The results support the design of the water harvesting system and
provide quantitative information for designing similar systems in the