The highest priority for flood management involved the Los Alamos Critical Experiments Facility (LACEF), a remote site for conducting research in nuclear criticality safety that housed substantial quantities of special nuclear material. The LACEF laboratories were in the bottom of Pajarito Canyon. To protect LACEF, a large, temporary "dry dam" was constructed in the canyon upstream of LACEF to temporarily contain flash floods that might result if an intense thunderstorm happened to rain heavily on the terrain drained by Pajarito Canyon. Runoff was monitored at multiple stations in the headwater streams above Pajarito Canyon.