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Spatial and temporal characteristics of rainfall in the United Arab Emirates (UAE) were investigated. The region is divided into four climate zones (East Coast, Mountains, Gravel Plains and Desert Foreland) of distinguished rainfall distribution. The rainfall patterns, rainfall probability of occurrences, rainfall intensity-duration-frequency (IDF) relationship, probable maximum precipitation (PMP) and drought scenarios were investigated. Daily rainfall data from a network of stations across the UAE were used. Standard statistical techniques were applied for data analyses. The Gumbel, log Pearson, generalized extreme value, log normal, Wakeby and Weibull probability distributions were tested to fit extreme rainfalls. Both Gumbel and Weibull distributions were found adequate. Measures of dispersion and symmetry of rainfall patterns were found relatively high. The estimated PMP values were found highest in the East Coast region and lowest in the Gravel Plains region. Estimated drought severity index showed that the regions have similar trends of drought patterns over the years. The study is useful for sustainable water resources planning and management in the region.

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An analytical model of flood wave propagation is used to study the sensitivity of dam-breach flood waves to breach-outflow hydrograph volume, peak discharge, and downstream-channel bed slope. Dimensionless parameters are identified for discharge and distance along the channel. A dam-breach Froude number is defined to enable analysis through a wide range of site and flow conditions. It is found that, at a certain distance downstream, the attenuated peak discharge is independent of the magnitude of the discharge at the breach site. This attenuated peak discharge is termed the ''ultimate discharge,'' and the distance associated with it, the ''ultimate distance.'' These ultimate values are a function, primarily of the downstream-channel bed slope and, secondarily, of the breach-outflow hydrograph volume.