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 verifies the basis for assignment of peak-flow qualification codes in the USGS National Water Information System (NWIS; https://doi.org/10.5066/F7P55KJN) to resolve ambiguity arising from the limited qualification codes available for special conditions. 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. Subcategories of 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. Data sources used to verify the basis for the codes included reports, online data, and USGS streamgaging notes.

This dataset summarizes selected basin and streamflow special conditions for USGS streamgages in Alaska that are commonly used for site and period of record selection for regional analyses, through water year 2022. The data consist of a table providing information about the type of streamflow available for the site, site special conditions related to the timing of data collection, basin special conditions related to drainage area and urbanization, and a summary of water years for daily mean streamflow and annual peak streamflow affected by regulation or outburst flooding. The data were compiled using peak-streamflow codes assigned in the USGS National Water Information System (NWIS; https://doi.org/10.5066/F7P55KJN), USGS publications, USGS streamgaging notes, and other sources.

This dataset summarizes selected basin and streamflow special conditions for USGS streamgages in Alaska that are commonly used for site and period of record selection for regional analyses, through water year 2022. The data consist of a table providing information about the type of streamflow available for the site, site special conditions related to the timing of data collection, basin special conditions related to drainage area and urbanization, and a summary of water years for daily mean streamflow and annual peak streamflow affected by regulation or outburst flooding. The data were compiled using peak-streamflow codes assigned in the USGS National Water Information System (NWIS; https://doi.org/10.5066/F7P55KJN), USGS publications, USGS streamgaging notes, and other sources.

This data release contains input data and results for an investigation of special conditions for peak streamflow and extreme floods for USGS streamgages in Alaska. Special conditions can include data-collection conditions, basin conditions, flood-generating mechanisms, or other information and can be critical for informing hydrologic analyses such as flood frequency analysis. The dataset contains three tables: (1) table of peak flows identified as extreme floods in Alaska through water year 2022, selected associated special conditions and climate information, and results of an assessment of flood-generating mechanisms, (2) a table of atmospheric river presence or absence data for Alaska for 1980-2019 that were used to assess peak-flow conditions, and (3) a table of input data and results for a drainage area-precipitation cluster analysis for 455 streamgages in Alaska.

This dataset contains selected information about U.S. Geological Survey (USGS) streamgages in Alaska that had at least 5 years of daily streamflow record through September 30, 2017. The goals for developing this dataset were to identify USGS streamgages that had at least 5 years of daily streamflow that responded mostly to seasonal meteorological inputs, that had a definable drainage basin above a minimum size from which basin characteristics could be determined, and that provided streamflow data not similar to another streamgage record in the dataset. Streamgages meeting these criteria for at least part of their records constituted the dataset for a study investigating seasonal flow regimes and streamflow drivers for Alaska. For 253 streamgages meeting selection criteria, data include period of record characteristics, basin characteristics, and flow regime cluster analysis results. The basin characteristics are provided in their original U.S. customary units and as values transformed to metric units. For an additional 78 streamgages, data include the special conditions affecting streamflow that disqualified the streamgage from the study, including recurring outburst floods, regulation, urbanization, hydrologic redundancy with another streamgage, drainage basin below minimum size, or an indeterminate drainage basin.

This data set contains selected information about U.S. Geological Survey (USGS) streamgages in Alaska that had at least 5 years of daily streamflow record through September 30, 2017. The goals for developing this dataset were to identify USGS streamgages that had at least 5 years of daily streamflow that responded mostly to seasonal meteorological inputs, that had a definable drainage basin above a minimum size from which basin characteristics could be determined, and that provided streamflow data not similar to another streamgage record in the dataset. Streamgages meeting these criteria for at least part of their records constituted the dataset for a study investigating seasonal flow regimes and streamflow drivers for Alaska. For 253 streamgages meeting selection criteria, data include period of record characteristics, basin characteristics, and flow regime cluster analysis results. The basin characteristics are provided in their original U.S. customary units and as values transformed to metric units. For an additional 78 streamgages, data include the special conditions affecting streamflow that disqualified the streamgage from the study, including recurring outburst floods, regulation, urbanization, hydrologic redundancy with another streamgage, drainage basin below minimum size, or an indeterminate drainage basin.

This dataset contains 474 drainage basin boundaries for U.S. Geological Survey (USGS) streamgages in Alaska, including supplemental drainage basin boundaries for alternate conditions for 3 of the 471 streamgages. The basin boundaries were delineated from the streamgage location to the nearest USGS Watershed Boundary Dataset (WBD) HUC boundary and along HUC boundaries from that intersection to the basin headwaters. The dataset also includes the streamgage locations used for delineation, which consist of points snapped from the streamgage coordinates in the USGS National Water Information System to the USGS National Hydrography Dataset flowline representing the respective streams. Streamgages selected for drainage basin delineation included: (1) streamgages having at least 10 years of peak-streamflow data through water year 2012, used for a statewide flood frequency study (Curran and others, 2016), and (2) streamgages in Cook Inlet Basin, regardless of record length, used for development of Cook Inlet Basin Streamstats in 2016 (https://streamstats.usgs.gov/ss/). For three streamgages, a supplemental drainage basin boundary was delineated for the drainage area associated with regulated (diverted) streamflow conditions contemporaneous with a period of streamflow record other than the present. Selected basins were previously published in the WBD as "NWISDrainageArea" features.

This dataset contains drainage basin boundaries for 253 U.S. Geological Survey (USGS) streamgages in Alaska that had at least 5 years of daily streamflow through September 30, 2017, three of which were delineated for alternate basin conditions. This compilation includes selected boundaries produced in 2014 (https://doi.org/10.5066/P143KNEJ). Additional basin boundaries were delineated from the streamgage location to the nearest USGS Watershed Boundary Dataset (WBD) HUC boundary and along HUC boundaries from that intersection to the basin headwaters. Streamgages selected for drainage basin delineation included streamgages in Alaska that met selection criteria for a statewide study of seasonal flow regimes (Curran and Biles, 2021). Sites for that study included USGS streamgages that had at least 5 years of daily streamflow that responded mostly to seasonal meteorological inputs, that had a definable drainage basin above a minimum size from which basin characteristics could be determined, and that provided streamflow data not similar to another streamgage record in the dataset. For three streamgages, the drainage basin boundary was delineated for the drainage area associated with regulated (diverted) or unregulated streamflow conditions contemporaneous with a period of streamflow record other than the present. Selected basins were previously published in the WBD as "NWISDrainageArea" features.

This dataset contains drainage basin boundaries for 253 U.S. Geological Survey (USGS) streamgages in Alaska that had at least 5 years of daily streamflow through September 30, 2017, three of which were delineated for alternate basin conditions. This compilation includes selected boundaries produced in 2014 (https://doi.org/10.5066/P143KNEJ). Additional basin boundaries were delineated from the streamgage location to the nearest USGS Watershed Boundary Dataset (WBD) HUC boundary and along HUC boundaries from that intersection to the basin headwaters. Streamgages selected for drainage basin delineation included streamgages in Alaska that met selection criteria for a statewide study of seasonal flow regimes (Curran and Biles, 2021). Sites for that study included USGS streamgages that had at least 5 years of daily streamflow that responded mostly to seasonal meteorological inputs, that had a definable drainage basin above a minimum size from which basin characteristics could be determined, and that provided streamflow data not similar to another streamgage record in the dataset. For three streamgages, the drainage basin boundary was delineated for the drainage area associated with regulated (diverted) or unregulated streamflow conditions contemporaneous with a period of streamflow record other than the present. Selected basins were previously published in the WBD as "NWISDrainageArea" features.

This data package contains 3 tables presenting site selection information, basin characteristics, subsidy to streamflow from glacier mass loss data, and other streamflow statistics for selected streamgages in Alaska that were used to evaluate the influence of glacier mass loss on streamflow in Alaska and conterminous basins in Canada. The first ("site_selection_outcomes.csv") contains streamgage identification and site selection or omission details for 728 streamgages. The second ("streamflow_statistics_eligible_gages.csv") includes observed mean annual streamflow for the period of record through September 30, 2022, observed or estimated mean annual streamflow for the period 2000-2019, and associated period of record information for 294 streamgages that met streamflow-related site selection criteria. The third ("basin_glacier_and_flow_data_2000_2019.csv") provides site, basin, streamflow, and streamflow component data for 116 streamgages that had glaciers in their basins, including seasonal flow regime identification from Curran and Biles (2020, 2021); glacier-related and other basin characteristics; observed streamflow period of record and values used; computed unsubsidized streamflow for 2000-2019; the subsidy to streamflow from glacier mass loss for 2000-2019, and other data. The final table also includes selected data ratios that were used for analysis, including specific streamflow values, the percent subsidy to streamflow from glacier mass loss, and the ratio of percent subsidy from glacier mass loss to percent glacier cover. For the purposes of this analysis, water years for streamflow data were equated with mass-balance years for glacier data.