Abstract
A collection of rainfall data and flood records for ephemeral channels in the Kingdom of Saudi Arabia (KSA) provided a unique opportunity to analyze the extreme records in such arid environment. Data of 3121 records were collected. A regional flood envelope relationships and other envelope curves in similar arid areas were compared with the current study. We found that the envelope of the maximum-recorded peak discharge versus basin area follows
The exponent falls in the range of the exponents in other arid basins. The enveloping curve for the volume versus basin area is
The parameters of the equation are significantly different from that of the arid Negev desert, Israel. Derived peak flow-volume relationship has the form
We found such relation is similar to arid/semi-arid southwestern United States but with slightly higher exponent and constant. When the peak discharge and maximum volume are plotted against their accompanied rainfall depth, p, linear envelope in log- log plot are developed for KSA region:
and
The equations predict the upper limit of the expected peak discharges and volumes that can be used for hydro-engineering applications in ungauged basins in the study region and regions a like. The developed envelope curves can also be used as an alternative or guide to performing rainfall-runoff modeling in KSA. The volume-area envelope equations have high degree of credibility since, 92% of the published data used for validation falls within the upper and lower envelope limits. These envelope curves have to be updated when more records are available.