Selected Peak-Flow Special Conditions for USGS Streamgages in Alaska

This data package documents selected special conditions affecting the magnitude of peak flows at streamgages in Alaska. The data consist of a table of special conditions for selected peak flows and a table of data sources. This dataset resolves ambiguity introduced by historical variations in USGS National Water Information System (NWIS; https://doi.org/10.5066/F7P55KJN) peak-flow code assignment practices or inherent in defining multiple possible conditions for a single code. For peak flows assigned a code 3 or 9 in the NWIS peak-flow database, the special conditions forming the basis for code assignment were (1) snowmelt or (2) a sudden release of water. Sudden releases of water included glacier dammed lake outburst, glacier and debris dammed lake outburst, sediment dammed lake outburst, mass failure/lake outburst, landslide debris dam breakup, beaver dam breakup, natural flow diversion, or subsidence from detonation subcategories. Data sources used to verify the basis for the codes included reports, online data, and USGS streamgaging notes.