Understanding colloid transport in soil is important for the ability to predict colloid and colloid-associated transport of contaminants and to protect soil and groundwater resources. Unsaturated porous media often serves as a representation of unsaturated soil thus providing a more general understanding of colloid retention mechanisms. While sample-scale (column) experiments provide the key data in colloid transport, pore-scale experiments involving various imaging techniques have become an additional valuable source of information. In unsaturated porous media, colloids can be potentially retained at solid-water interface (SWI), air-water interface (AWI), and contact line. In particular, the retention at AWI and contact line is in general poorly understood. While the solution chemistry parameters such as pH and ionic strength and surface properties of colloids and porous media have been extensively investigated, more recent studies suggest the importance of hydrodynamics in colloid retention. The first part of the present study is a pore-scale experimental investigation of colloid retention employing a microfluidic channel and a confocal microscope. The micromodel visualization focuses on colloid behavior in the interfacial region (AWI and contact line) under dynamic conditions, with different interface velocities of both advancing and receding interfaces. Hydrodynamic conditions have been shown to affect colloid retention at AWI and contact line by affecting colloid availability for the retention as well as affecting the efficiency of colloid interfacial interactions. Relative preference of AWI and contact line for colloid retention has been analyzed. The second part is the development of a computational approach to simulate the viscous flow and colloid transport near the AWI and moving contact line. A mesoscopic multiphase lattice Boltzmann method and a Navier-Stokes based volume-of-fluid method are applied simultaneously to simulate the interfacial flow. The trajectories of colloids are then integrated numerically by solving the colloid's equation of motion, under the influence of physicochemical, hydrodynamic, capillary, Brownian and body forces and torques. Results from the computational approach will be compared to the micromodel observations, including the shape of the air-water interface and distribution of colloids near AWI and contact line.