Editing DnD Desert Raiders Campaign Natural Hazards (section)

==== Sand Dunes ====
Most people immediately think of sand dunes when they imagine a desert, but in fact many kinds of waste have no dunes at all. Winds carry away soil, sand, and even light pebbles, leaving behind a thin "pavement" of larger stones. Dried lake beds are plains of cracked mud crusted with salt. Lava flows cover the land with humped, rough stone. Still, hardy grasses and undergrowth do exist in some parts of the waste, catching grains of sand and holding them in place long enough for immense “waves" to grow.
Sand dunes are wandering things, although the mundane variety travels no more than a couple of hundred feet in a year. This is enough to eventually overrun farmland and choke out forests, but it is not an immediate hazard to roost creatures. However, the constant action of wind on sand produces potentially hazardous situations.
'''Collapse:''' A sand dune has a long, shallow back slope shaped by the wind and a sharp leading edge with a steep drop on the lee side. This edge is precarious, with the pull of gravity just balanced by the tendency of sand grains to stick together. Coarser sand or lighter gravity produces higher and steeper dunes, while fine grains or heavier gravity produces low dunes with gentler slopes. However, the wind can swiftly shift the balance, blowing sand off the edge and triggering a sudden collapse. A collapsing dune is every bit as dangerous as an avalanche and follows the same rules (as described on page 90 of the Dungeon Master’s Guide).
'''Blowout:''' A change in wind direction can produce a blowout, hollowing out the center of a dune and leaving a large cavity. This cavity is not always visible, and a thin layer of safe-looking sand might cover a vast tomb that swallows people and animals without a trace. The crust covering a blowout is too weak to support any creature larger than Tiny. Noticing a blowout requires a successful DC 10 Survival check; however, charging or running characters are not entitled to a check. Characters enveloped by the sand begin to take damage and suffocate as though trapped by an avalanche. A blowout hides in one out of every one hundred sand dunes (1% chance).
Sand dunes that have been stabilized by grasses or shrubby trees are much less likely to collapse. Still, even such a place can hide a blowout if the undergrowth in the area is thin.