Transport in heterogeneous porous media under natural and anthropogenic forcing often departs from classical steady, Fickian descriptions because of nonlinearity, temporal variability, and structural disorder. This body of work investigates how medium heterogeneity and transient forcing—such as oscillatory boundary conditions and tides—jointly control displacement-front evolution, solute containment, and the emergence of chaotic mixing. The approach integrates Lagrangian particle tracking, stochastic and perturbation analyses, Green’s-function formulations, and time-dependent upscaling frameworks, including CTRW-based descriptions, to connect pore- to field-scale transport under both steady and transient flows. The results show that heterogeneity leads to non-Fickian, time-dependent dispersion of displacement fronts, while transient forcing interacting with heterogeneity creates mixed phase-space structures in which trapping and chaotic regions coexist, producing solute containment alongside enhanced mixing. In coastal aquifers, tidal forcing further strengthens trapping and chaotic advection, strongly modulating residence times and mixing efficiency. Together, these findings establish a unified framework for nonlinear and chaotic transport in heterogeneous porous media, clarify why steady linear models fail, and provide physically based tools to predict spreading, containment, and mixing relevant to contaminant fate, coastal groundwater dynamics, and subsurface energy applications.