The Aguirre Spring debris flow of August 14, 1991
— Loretta M. Heckman and Jerry E. Mueller

A meso-scale convective storm in the White Sands-Aguirre Spring area during the late evening and early morning hours of August 13-14, 1991, initiated a major flow event in the basin of Anvil Creek, a long, narrow watershed that heads just below the Needles on the east side of the Organ Mountains. Field evidence indicates that the flow in its upper reaches was confined to the north branch of Anvil Creek where the channel was greatly modified and enlarged, producing a chute-like bed of polished bedrock. At the lower end of the bedrock channel, the flow followed the natural bend of the north branch to the north-northeast, depositing a viscous lobe of boulders encased in a matrix of gravelly grus. A subsequent flow failed to negotiate the turn, instead surging ahead to enlarge a breach in a narrow divide between the north branch and south branch of Anvil Creek. Cross-sectional measurements of the active channel of Anvil Creek upstream of the breach produce estimated peak water discharges that are unrealistically high for such a small basin. In addition, there is no evidence for major flood discharges on the valley floor downstream of the lobe. The lobe that plugs the floor of the former north branch of Anvil Creek rafted large boulders and relatively unscarred trees, plus inundated the bases of many large shrubs and trees, in most cases without any damage. Downstream of the breach along the active channel of the south branch, the flow built marginal rock levees, often with the largest boulders on top instead of on the bottom, a feature diagnostic of a slow-moving, viscous flow. The inescapable conclusion is that the event of August 14, 1991, was not a simple water flood, but rather a localized debris flow.