Using radar rainfall to explain the occurrence of a 2012 soil slip near Mt. LeConte, TN, USA

A storm on August 5, 2012, triggered a soil slip that mobilized into a debris flow in a relatively remote part of Great Smoky Mountains National Park, 2 km southwest of Mt. LeConte, TN. A rain gauge at Mt. LeConte Resort, recorded manually at 07:00 Eastern Time each day, reported 92.46 mm of rainfall on August 6, 2012, to the National Weather Service. Near Composite Reflectivity (NCR) and Digital Precipitation Array (DPA) products from the Knoxville, TN, NEXRAD Doppler weather radar station for August 5 and 6, 2012, were used to infer the storm's rainfall intensity and duration details. NCR products consist of the maximum radar reflectivity value from all 14 elevation angles scanned for each 1.09 km (super 2) cell, which users must convert to precipitation depth. DPA products are rain rate (in./hr) calculated with a National Weather Service model that uses radar reflectivity and automated rain gauge measurements to assign regional bias factors to each complete radar scan of the atmosphere surrounding the radar station using a national grid system composed of 17.12 km (super 2) cells. Cumulative NCR inferred rain depth was 90.65 mm at the Mt. LeConte gauge location and 69.23 mm at the soil slip location. The cumulative DPA rain depth was 47.64 mm at the gauge. The maximum 15 minute NCR precipitation intensity was 39.61 mm/hr at the Mt. LeConte gauge location and 63.24 mm/hr at the soil slip location. The timing of the soil slip probably coincided with a 20-minute-long interval of maximum intensity precipitation.