National Landslide Preparedness Act This bill directs the U.S. Geological Survey (USGS) to establish a National Landslide Hazards Reduction Program to identify and understand landslide hazards and risks, reduce losses from landslides, protect communities at risk of landslide hazards, and help improve communication and emergency preparedness. The USGS shall, among other things develop and publish a national strategy for landslide hazards, risk reduction, and response in the United States (including territories); develop and maintain a publicly accessible national landslide hazard and risk inventory database; expand the early warning system for debris flow; and establish emergency response procedures for the rapid deployment of federal scientists, equipment, and services to areas impacted by a significant landslide event. The USGS may provide grants to research, map, assess, and collect data on landslide hazards. The National Science Foundation may provide grants to eligible entities for landslide research. The USGS (1) shall advance the identification, mapping, research, monitoring, restoration, and mitigation of subsidence and groundwater resource accounting, losses from subsidence, including saltwater intrusion, particularly in areas affected by drought and sea level rise; (2) shall establish the 3D Elevation Program and the 3D Elevation Federal Interagency Coordinating Committee; and (3) may make grants and enter into cooperative agreements to facilitate the improvement of nationwide coverage of 3D elevation data.