  We propose a dual scale drift-diffusion model for interfacial growth and
etching processes. The two scales are: (i) a depletion layer width surrounding
the aggregate and (ii) a drift length.The interplay between these two
antithetical scales yields a variety of distinct morphologies reported in
electrochemical deposition of metals, viscous fingering in fluids and in porous
silicon formation. Further, our algorithm interpolates between existing growth
models (diffusion limited aggregation, ballistic deposition and Eden) for
limiting values of these variables.
