Mohsen Sherif

A flash flood is the most common natural hazard that endangers people’s lives, the economy, and infrastructure. Watershed management and planning are essential for reducing flood damages, particularly in residential areas, and mapping flash flood-sensitive zones. Flash flooding is an interface dynamic between geoterrain system factors such as geology, geomorphology, soil, drainage density, slope, and flood, rather than only water movement from higher to lower elevation. Consequently, the vulnerability to flash floods necessitates an awareness of and mapping topographical features. A flash flood vulnerable zones (FFVZ) map is essential for thorough flash flood risk assessment and management to minimize its detrimental effects, particularly in residential areas, especially in cities like Fujairah with seven wadis flowing into the city and even though it has two main dams and fifteen breaker dams. So, in this work, eight satellite image-derived parameters rainfall, elevation, slope, land use/land cover (LULC), drainage density, geology, geomorphology, and soil were combined to predict the flash flood-vulnerable zones using a weighted overlay technique based on geographic information systems (GIS). Each element of the thematic maps is ranked and weighted according to how vulnerable it is to flash floods in the study area, with 55 km2 being classified as a very highly vulnerable area, 78 km2 as a high-risk area, 9.3 km2 as a moderate risk area, 70 km2 as a low vulnerable area, and 257 km2 as a very low vulnerable area. In addition, places with a very high vulnerability level include the Fujairah Airport, Fujairah Port, some residential neighborhoods in the city’s center, oil storage areas, two hospitals, and universities. Additionally, from 1990 to the present, Landsat and Sentinel 2 data showed consistent changes in vegetation and built-up areas. Therefore, in addition to helping policy and decision-makers make the best choices about the efficacy of the study area’s protective structures against the risk of flash floods in the future, the results can also be a valuable source of information.

Accurate and continuous rainfall monitoring is essential for effective water resources management, especially in arid and semi-arid regions such as the United Arab Emirates (UAE). Significant spatio-temporal precipitation variation in the UAE necessitates the use of the latest techniques to measure rainfall intensity accurately. This study investigates the consistency and applicability of four satellite precipitation products, namely PERSIANN, PERSIANN-CCS, PERSIANN-CDR, and PDIR-Now, over the UAE. Daily time series data from 2011 to 2020 were analyzed using various statistical measures and climate indices to develop the belief in the products and for their inter-comparison. The analysis revealed that the average probability of detection (POD) for PDIR and CDR was the highest, with values ranging from 0.7–0.9 and 0.6–0.9, respectively. Similarly, CDR has a better Heidke Skill Score (HSS) with an average value of 0.26. CDR outperformed its counterparts with an average correlation coefficient value of 0.70 vs. 0.65, 0.40, and 0.34 for PDIR, CCS, and PERSIANN, respectively. Precipitation indices analysis revealed that all the products overestimated the number of consecutive wet days by 15–20%, while underestimating consecutive dry days by 5–10%. The quantitative estimations indicate that all the products were matching with the gauge values during the wet months (January–April), while they showed significant overestimation during the dry months. CDR and PDIR were in close agreement with the gauge data in terms of maximum daily rainfall with an error of less than 10% for both products. As compared to others, PERSIANN-CDR provided better estimates, particularly in terms of capturing extreme rainfall events and spatial distribution of rainfall. This study provides the first comprehensive evaluation of four PERSIANN family products based on recent daily rainfall data of UAE. The findings can provide future insights into the applicability and improvement of PERSIANN products in arid and semi-arid regions.

Groundwater extraction in most Middle East and North Africa (MENA) countries far exceeds its renewability, which ranges from 6% to 100%. Freshwater resources to support food production are very limited in this region. Future climate predictions include more consistent and longer wet periods with increasing surplus rainfall, which will enhance flood and flash flood occurrences in the MENA. Demand management of groundwater resources and managed aquifer recharge (MAR, also called groundwater replenishment, water banking, and artificial recharge, is the purposeful recharge of water to aquifers for subsequent recovery or environmental benefits) represent essential strategies to overcome the challenges associated with groundwater depletion and climate change impacts. Such strategies would enable the development of groundwater resources in the MENA region by minimizing the stress placed on these resources, as well as reducing deterioration in groundwater quality. Groundwater augmentation through recharge dams is a common practice in different countries around the globe. Most dams in the MENA region were built to enhance groundwater recharge, and even the few protection dams also act as recharge dams in one way or another. However, the operating systems of these dams are mostly dependent on the natural infiltration of the accumulated water in the reservoir area, with limited application of MAR. This review presents analyses of groundwater renewability and the effectiveness of recharge dams on groundwater recharge, as well as the potential of MAR technology. This study indicates that the recharge efficiency of dam’s ranges between 15 to 47% and is clustered more around the lower limit. Efficiency is reduced by the clogging of the reservoir bed with fine materials. Therefore, there is a need to improve the operation of dams using MAR technology.