Tidal elevation, discharge, and tidal basin area data from southwest Bangladesh (collected August-September 2015)

Discharge data collected from tidal channels in the Polder 32 region of southwest Bangladesh, in the tidally-maintained region of the Ganges-Brahmaputra-Meghna Delta. The datasets span (or have been extrapolated to span) one semidiurnal period at each of six locations. The raw data were collected in August and September 2015 using a boat-mounted acoustic Doppler current profiler (ADCP) sampling at 1 Hz with autonomous GPS positioning. The measured velocities were then converted to discharge by calculating the flux through the area under the boat's transect. Systematic variations in measurements between oppositely-oriented transects were corrected by averaging pairs of consecutive transects to produce the final dataset recorded in this spreadsheet.<br>Tidal elevation data were collected at seven stations in the Polder 32 region of southwest Bangladesh over one spring-neap cycle in August-September 2015 using an array of pressure sensors (HOBO loggers and Schlumberger CTDs). Pressure was converted to depth by subtracting atmospheric pressure and then applying a conversion factor of 9.9 kPa/m. Elevations are strictly local to the sensor and were not surveyed to a common vertical datum. A smoothing spline interpolant was applied during post-processing to fill gaps in the datasets around low water when several of the instruments were subaerially exposed.<br>The KML files show the planform area of the channels at various tidal stages (lowest low water, the bankfull elevation, and highest high water) before polder construction, in the 1970s, and in 2015. These were manually digitized using Google Earth imagery (modern configuration) or the earliest available Landsat imagery (1970s data). Each polygon has fields indicating our estimate of tidal range, planform area, and the volume of water stored at that location between low and high water. In conjunction with the discharge data, these spatial data are useful for determining the size of the tidal basin which a given channel fills and drains.