Answer:
a trellis drainage pattern forms when tributaries join the main river at right angles.it froms in a ridge-and-valley landscape,where rocks that have unequal resistance to erosion are folded into series of anticlines and syclines.
the rivers bandon, lee and blackwater have trellis pattern.these developed when the softer limestone that occupied the anticlineswas eroded,leaving the more resistant sandstone anticlines standing out.
the rivers that occupy many glaciated valleys, including the gap of dunloe, also have trellis pattern.