ON-006-18D Alluvial Fan Mapping of Pitkin County, Colorado (Data) - v20251201 Download Publication Details The Colorado Geological Survey develops and provides a variety of geologic hazard maps for various state and local governments with land use and hazard mitigation planning in mind. To prepare for post-wildfire natural hazards, the CGS has mapped alluvial fans as well as high-angle fans and (or) debris fans. Areas with these landforms are at risk for debris flows and (or) mudflows, especially after wildfire events. Using available Colorado LiDAR datasets, both known and previously unrecognized alluvial fans were compiled, mapped, and defined. This map is part of a statewide effort to develop county-specific maps of alluvial fans in Colorado. Digital ZIP download. ON-006-18D – v20251201 IMPORTANT NOTE: This file contains all relevant GIS data as of December 1, 2025. When new data is incorporated, this data package will be updated with a new version number corresponding to the date of issue. The GIS datasets are available for viewing via our online Web Map Portal: ON-006-18D Alluvial Fan Mapping of Pitkin County, Colorado (Map) Citations Crandall, Amy, Zhou, Wendy, and Lovekin, J.R., 2025, Alluvial fan mapping of Pitkin County, Colorado (data) – v20251201: Colorado Geological Survey Online Series 006-18D. https://doi.org/10.58783/cgs.on00618d.esuv8817 [Also available at https://coloradogeologicalsurvey.org/publications/alluvial-fan-map-data-pitkin-colorado/].