Evaluation of the Landslide Potential in Capulin Canyon following the Dome Fire, Bandelier National Monument, New Mexico

Cannon, Susan; Ellis, William; Godt, Jonathan

The Dome fire burned 6684 ha in Bandelier National Monument and the adja- cent Santa Fe National Forest in New Mexico. To assess the present stability of the Boundary Peak and Base Camp landslides in Capulin Canyon, and to evaluate the potential for a change in stability due to the removal of vegetation during the fire, a program of mapping and soil-moisture monitoring was undertaken. The Boundary Peak landslide covers an area of approximately 2.9 km2, and appears to be approximately 150 meters thick, while the Base Camp landslide covers approximately 0.2 km2. The thickness of the Base Camp landslide deposits is not known. The Boundary Peak landslide deposits experienced two areas of high burn intensity which cover a total area of approximately 0.15 km2. The remainder of the deposits were mapped as moderate or low burn intensities. The Base Camp deposits show one area of low burn intensity which covers an area of 0.03 km2. Neither the Boundary Peak and Base Camp landslide deposits exhibit evidence of recent movement or instability. Both landslide deposits are mantled by the 50,000 to 60,000 year- old El Cajete pumice; deposition of the pumice appears to postdate the last movement of the landslides. The entire landslide topography is muted and subdued. No cracks, fissures or shear zones were observed, and only a few tilted trees, too few and far between to indicate instability of the deposits, were observed. The present-day interaction of Capulin Creek and the landslide toes appears to be negligible, and no danger of destabilization of the deposits by undercutting appears to exist at this time. The likelihood of reactivation of the Base Camp landslide deposits due to increased infiltration in areas burned by the Dome fire appears to be negligible due to the small area and low intensity of the fire on the deposits. Qualitative evaluation of soil-moisture data from the Boundary Peak landslide deposits indi- cates that (1) over time, and with continued rainfall, moisture infiltrates to greater depths at the burned site than at the unburned site, and (2) the soil at the burned site stays relatively moist throughout the summer monsoon season, while the unburned site dries out rapidly with the onset of warm temperatures. These differences may be due to the lack of vegetation- induced transpiration at the burned sites. Further evaluation is necessary to determine if the increased infiltration could potentially destabilize the landslide deposits.

Evaluation of the Landslide Potential in Capulin Canyon following the Dome Fire, Bandelier National Monument, New Mexico

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