The 3 August 2014 Ludian, China, M_s = 6.5 earthquake caused many large landslides. The biggest occurred at Hongshiyan near the epicenter, had a volume of 1.0  ×  10⁷ m³ and dammed the Niulanjiang River, creating a large lake. Post-event field investigations yielded detailed data on the rock structure, the local lithology and geometry of the landslide dam and composition and grain sizes of the debris avalanche. Based on these data, this work analyzes the geology and topography of the Hongshiyan area.