Land Use Policy at a Climatic Crossroads: Valuing the Cost of Sea-Level Rise Inaction in Egypt’s Nile Delta

The Nile Delta, a critical nexus of agricultural, urban, and industrial land uses, faces profound risks from sea-level rise (SLR) that challenge Egypt's national land use policy and coastal governance frameworks. This paper provides a spatially explicit economic assessment of a "no-action" policy scenario, quantifying the consequences of failing to implement adaptive land management. Using a high-resolution Digital Elevation Model and a 'bathtub' inundation model under IPCC SSP2-4.5 and SSP5-8.5 scenarios, we project the inundation of different land use types. These physical impact models are integrated with sub-national socioeconomic data to value the loss of agricultural land, damage to built-up assets, and the costs of population displacement across 16 coastal land management units. Our findings reveal catastrophic economic consequences of policy inaction, with projected damages reaching multi-trillion Egyptian pounds (L.E.) by 2100. The spatial analysis highlights a severe concentration of risk in the low-lying governorates of the Nile Delta and the megacity of Alexandria, indicating that current land use patterns are misaligned with future climate realities. The non-linear escalation of costs underscores a rapidly closing window for proactive spatial planning and cost-effective adaptation. We conclude that the economic costs of inaction—representing a failure of anticipatory land use governance—vastly exceed the investment required for adaptive measures. This study provides a data-driven rationale for integrating SLR projections into all levels of land use planning, from national strategy to local permitting, to secure Egypt's economic base, food security, and social stability.