Valuing Groundwater Impacts for Sustainable Urban Planning in Coastal Cities

Groundwater is a critical yet often invisible resource underpinning the resilience of urban areas, particularly in coastal zones facing climate change. Despite its importance, groundwater is systematically undervalued and poorly integrated into urban planning and policy, leading to unsustainable development pathways. This paper introduces a novel Integrated Hydro-Economic Valuation Framework designed to make the economic consequences of groundwater changes visible and actionable for urban decision-makers. The framework links physical hydrogeological changes to impacts on urban systems and quantifies them in monetary terms. We apply this framework to a comprehensive case study of Egypt's Mediterranean coast, a rapidly urbanizing region representative of many coastal zones in the Global South. Using a high-emissions climate scenario (RCP8.5), we project rising groundwater levels due to sea-level rise and value the subsequent damages to agriculture and road infrastructure across 16 coastal units through 2100. The results reveal substantial and escalating economic costs, projected to reach billions of L.E., with over 98% of the damage concentrated in the densely populated urban and economic hubs of the Nile Delta, including Alexandria. These findings demonstrate that failing to account for groundwater changes creates a massive, unfunded liability that threatens municipal solvency and long-term sustainability. The paper concludes by providing concrete policy recommendations for integrating these valuation outcomes into risk-informed urban planning, infrastructure investment, and climate adaptation strategies. This research provides a robust, replicable methodology for cities worldwide to quantify the hidden costs of groundwater degradation and recalibrate their development trajectories for a water-secure future.