<p>Although the uncontrolled downward migration of NAPL and the expansion of the contaminated region are of particular concern, it has been shown that the remobilization of DNAPL can improve remediation efficiency by enlarging the total NAPL-water interfacial area for mass transfer during surfactant-enhanced aquifer remediation (SEAR). However, the driving forces influencing the redistribution morphology have not been sufficiently discussed. This study first combines trapping numbers (N_Ca and N_B) with the morphological characteristics of the contaminated zone to investigate their roles in the remobilization process of DNAPL. A 2-D sandbox apparatus was used to simulate the remobilization of 1,2-dichloroethane (1,2-DCA) pooled on an arc-shaped lens with low permeability in SEAR. The area, lateral distance, and vertical distance used to characterize morphological redistribution were determined by digital image analysis. Driving forces such as viscous force, gravity force, and capillary force were analyzed using the trapping numbers: capillary number (N_Ca) and Bond number (N_B). The results showed that the redistribution area consisted of two distinct parts, induced by remobilization of the surface layer (Part 1) and the inner layer (Part 2), respectively. In terms of pre-to-post remobilization, viscous forces played a greater role in Part 1, while buoyancy forces were more significant in Part 2 due to bypass flow. The redistribution area and lateral distance were positively correlated with the N_Ca of Part 1, while vertical distance had a negative relationship with N_B. However, the redistribution area of Part 2 had a negative relationship with N_B, so do the lateral distance and vertical distance. These results implying that trapping numbers can be used to manipulate injection parameters in SEAR, thereby promoting remediation efficiency and controlling the enlargement of the area and vertical migration simultaneously.</p> Graphical Abstract <p></p>