Urban Geology: Challenges and Opportunities in Rapidly Expanding Cities

The study of geological materials, processes, and groundwater systems in relation to the built environment is known as urban geology and is growing in significance as the surface area of cities and their subsurface complexity continue to expand rapidly. This is a review of the existing knowledge on the geological nature of urban settings and the assessment of the obstacles and opportunities presented in fast-growing cities. Cities also tend to cover a wide range of different sedimentary sequences and altered topography, as well as have a large amount of artificial substrate that makes stratigraphy difficult to understand, geotechnics difficult to predict, and hydrogeology harder to connect. Rapid urbanization may increase geohazards, such as landslides, floods, seismic shaking impact, sinkholes, and land subsidence caused by groundwater extraction. Simultaneously, urbanization stresses groundwater resources and predisposes them to long-term contamination in the underground, which is determined by the heterogeneity of geological formations and the historical background of infrastructure. The review emphasizes the role of urban geology in reducing risk via hazard zonation, site characterization and monitoring, and sustainable development via geology-informed land-use planning, resilient infrastructure design, and strategic control of the use of subsurface space for transport, utilities, and to develop low-carbon energy resources like geothermal systems. The solution to the urban underground data problem is greatly enhanced by progress in remote sensing, near-surface geophysics, and 3D geological modeling, but cannot be effectively adopted due to gaps in data, fragmented governance, and a lack of cross-disciplinary integration. In order to achieve safer and more sustainable cities, there is a need to strengthen urban geological databases, policy frameworks, and capacity building.