We find an interesting pattern of deposition and ablation occurring when flowing alginate and calcium solutions at constant flow rates through microfluidic channels meeting in a Y-shaped junction. The alignment between pressure measurements and microscopy demonstrates that the gel deposit grows to occlude the channel and thus necessitates an increase in driving pressure to maintain the constant flow rate. This growth continues until shear stress pulls the gel off the wall, resulting in the ablation of the gel. The ablated gel maintains its shape to form stable rod structures several hundred microns long and 30 microns wide, the same width as the channel. Gel deposition and ablation happen with a regular frequency. We further find that we can control both the extent of the deposition and the frequency of ablation events by varying flow rate, the degree of crosslinking, and the concentration of gel.