The October 2015 storm in Alexandria led to flooding of historical proportions. Although this October storm was a rare event (≈1:50 year), it could have been predicted at least 1 week in advance. If an appropriate warning system had been in place, measures could have been taken to alleviate its consequences. Therefore, the use of rainfall forecasting in storm water modelling can be one of the first useful and cheap mitigation measures. This forecasting system may further allow employing Anticipatory Water Management. The latter would imply that a large extra retention reservoir would be made available by pumping the water out from lakes of the city (Lake Maryot and Airport Lake) before it rains. Further research will be required to assess the technical and economic aspects of this option. The high variability and uncertainty of rainfall call for a robust and flexible strategy for Alexandria, which considers a portfolio of measures able to absorb the negative consequences of extreme events (designed for exceedance). This strategy should enable the responsible authorities to map out the future of the drainage system across the city over the next two or three decades and to identify the tipping point when upgrading of the existing drainage and irrigation system will be required. It will also provide the required evidence base on which a long-term wastewater and sewerage plan for Alexandria City should be implemented.

Background: The architected mechanical metastructures have garnered significant research attention for various engineering applications due to their remarkable mechanical properties and unique deformation behavior. The lattice-based micro-structured materials have shown enhanced mechanical properties and the ability to control wave propagation, making them ideal for multifunctional applications. Objective: We report the family of lattice-based hourglass metastructures within the optimal design scope and its geometrical parameter selection. The lattice-based energy absorption performance and their damping characteristics have been classified based on different constitutive lattices. Methods: Herein, the uniaxial compressive response and lattice-based energy absorption capacity of a novel hybrid configuration, hourglass-shaped, consists of auxetic and honeycomb-based lattice, are systematically investigated through theoretical, finite element simulation and experimental methods. The proposed hourglass-shaped unit cell is a combination of two oppositely oriented coaxial domes that give more flexibility to control dynamic response and enhance lattice functionality passively. An additive manufacturing route has fabricated a series of hourglass-shaped lattice metastructures with nylon-based material. Results: It was found from the experimental data that the Ideal energy absorption efficiency parameter (E _i) is highest for the case of the auxetic-based hourglass with the increment of 22% and 35% than the solid shell and honeycomb lattice-based metastructure, respectively. The specific energy absorption parameters data have also been evaluated and compared with the numerical computational results. Conclusion: The combination of numerical simulation, additive layer manufacturing (3D printing), and experimental testing are implemented to quantitatively determine the lattice-based energy absorption properties and justify their evaluation. This study suggests the utilization of novel hourglass lattice-based metastructure for multifunctional engineering applications.