Your liner should be visually inspected after every major weather event, and routinely checked for uplifting, tears, or other kinds of damage. Even if you've completely cleared your installation site of all rocks, debris, and other damaging materials, more may appear as the earth settles. Roots or submerged rocks can make their way up through the ground to damage your liner. A protective underlayment may be a valuable addition to protect your geomembrane even further.
Underlayments for geomembrane liners can come in a wide array of options, from other geomembranes, to geotextiles that act as a kind of protective "net".