Dataset for: Weak and uncertain effects of flood dynamics on a protected diving beetle Graphoderus bilineatus: insights from opportunistic presence–absence data General Information Authors: Martin Drenovácz, Vojtěch Kolář, David Boukal, Zoltán CsabaiCorresponding Author: Martin Drenovácz, drenovaczmartin@gmail.comDate of Data Collection: 2000-2022Geographic Location: Bodrog, Tisza, Danube, and Drava river catchments, Hungary. Data Sharing and Access Restrictions This dataset contains occurrence records and derived hydrological variables used to model the presence/absence of Graphoderus bilineatus. Note on Hydrological Data: Due to data sharing constraints and licensing agreements with the Hungarian General Directorate of Water Management (Országos Vízügyi Igazgatóság - OVF), raw daily flood water level data cannot be published in this repository. A such, the flood_water_level column only contains N/A placeholders. Researchers wishing to access the raw daily hydrological time-series must request them directly from OVF. File Overview Filename: G_bilineatus_flood_data.csv Format: Comma-separated values (.csv) Missing Data: Missing or non-applicable values are denoted by N/A. Data Dictionary (Column Descriptions) lat: Latitude of the sampling site (in decimal degrees, WGS84). lon: Longitude of the sampling site (in decimal degrees, WGS84). locality: Name or description of the sampling site (e.g., specific oxbow lake or pond). river: Main river catchment associated with the floodplain habitat (Bodrog, Danube, Drava, or Tisza). date: Date of the sampling event (Format: DD.MM.YYYY). year: Year of the sampling event. month: Month of the sampling event. present: Occurrence status of Graphoderus bilineatus at the site during the sampling event (present or absent). present2: Binary occurrence status used for logistic regression modeling (1 = present, 0 = absent). N.specimens: Number of individual beetles collected or observed. Contains numeric counts or minimum estimates (e.g., 1+, 2+). For absences, this value is 0. trapping: The method used for sampling the invertebrates (e.g., net, trap). Marked as N/A if no standardized method was recorded or for opportunistic observations. days_last_flood: Number of days elapsed between the end of the most recent flood event (see date_passed) and the sampling date. days_last_spring_flood: Number of days elapsed between the end of the most recent spring flood event (defined as events peaking in May-June) and the sampling date. spring_flood_duration: Duration (in days) of the most recent spring flood event. Calculated as the difference between the starting date (when water surpassed the threshold) and the closing date (date_passed). spring_flood_max_cm: Maximum water level (in cm) recorded above the local flood threshold during the spring flood event. spring_flood_mean_cm: Mean water level (in cm) recorded above the local flood threshold during the spring flood event. water_meter: Name of the official OVF water gauge station used to calculate the hydrological metrics for the corresponding locality (e.g., Felsőberecki vízmérce, Mohács vízmérce). water_level: Threshold water level (in cm) specific to the gauge station used to define a "flood event". date_passed: The closing date of the most recent flood event, defined as the day the water level dropped back below the local threshold (Format: DD.MM.YYYY).