1. A method for gathering materials on an ocean surface, comprising: determining, using a computer processor, an initial distribution of material based on observational sources; representing the material by a plurality of particles in a numerical ocean model; determining a plurality of trajectories for the numerical ocean model based on modeled surface currents data; computing a plurality of velocity gradients along a corresponding trajectory of the plurality of trajectories for each of the plurality of particles based on the initial distribution; computing a plurality of deformation tensors for each of the plurality of particles based on the plurality of velocity gradients; determining a dilation for each of the plurality of deformation tensors based on a divergence from a corresponding local velocity gradient of the plurality of velocity gradients of a corresponding particle of the plurality of particles, wherein the dilation is determined according to: 1 Δ ⁢ D ⁢ ⁢ Δ D ⁢ ⁢ t = ∇ · v ⁡ ( x ⁡ ( t ) ) , and wherein D D ⁢ ⁢ t is a total derivative along a material trajectory, Δ is the dilation, and ∇·v(x(t)) is a time series of divergence along the corresponding trajectory x(t); generating a dilation map for the plurality of particles based on the dilation of a time step tensor of the plurality of deformation tensors for each of the plurality of particles; using the dilation map to identify a target area with a higher area density; create a recovery path that navigates a recovery ship through the target area; and monitoring collection of the plurality of particles based on the dilation map.