A vast array of processes in geophysics (compaction of sedimentary basins), industry (paper manufacture and coffee extraction) and even the human body (transport of materials through the digestive system) involve the compaction of porous, elastic, layers by a pressure-driven flow. The nature of this compaction has been studied in depth (see, for example, Hewitt et al. Phys Rev. E. 93:023116 (2016)), including the dependence of the flow rate on the pressure head and the amount of elastic deformation this induces, but the stability of these compacted profiles has not been investigated as thoroughly. In this talk, I'll outline some work in progress (...that I promised Duncan would be ready by sometime in March 2024) towards this goal, showing how a compacted hydrogel layer is, under certain circumstances, unstable to channel formation, and how the stability properties depend on the permeability and pressure head, as would be expected, but also on the proportion of 'bound water' in the gel scaffold and the shear stiffness (in a potentially unexpected way).