How can low-pressure channels and deforming tills coexist subglacially?

Deforming till and low-pressure water channels are observed to coexist subglacially, but till also is observed to creep rapidly into low-pressure sub-glacial regions. A simple model shows that these observations are not contradictory. Creep of a thin till to a low-pressure region can occur from a narrow zone only, and will lead to isolation of channels from till farther away. -Author