The physical characterization of hydrogeological processes in urban areas is based on a description of their hydraulic properties and water flow phenomena for both unsaturated and saturated media. The unsaturated zone is described in terms of water flow characteristics. Techniques for quantifying soil properties play a key role in determining the division of rainwater into surface runoff and infiltration. Description of groundwater flow in porous, fractured, and karst media are described based on specific principles, concepts, approaches, and the corresponding equations for specific media. For different utility networks (water distribution, sewage, drainage systems, and others) the principles of water flow provide the bases for understanding the interaction with surrounding media including groundwater. The hydraulic interaction of groundwater with different types of underground infrastructure elements is based on analyses of types of hydraulic effects, the barrier effect, uplift pressures and forces, internal erosion, and preferential flow paths.