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.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.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.本数据集采集自孟加拉国西南部32号圩田（Polder 32）区域（恒河-布拉马普特拉河-梅格纳三角洲潮汐维持区）内潮汐水道的流量数据。数据集在6个测点分别覆盖（或经外推覆盖）一个半日潮周期。原始数据采集于2015年8-9月，采用船载声学多普勒流速剖面仪（acoustic Doppler current profiler, ADCP）进行采集，采样频率为1 Hz，并搭载自主GPS定位系统。通过计算船载断面下方的过水通量，将实测流速转换为流量数据。针对反向布设断面间测量存在的系统偏差，通过对连续两组反向断面数据取平均的方式进行校正，最终得到本表格中记录的数据集。 潮汐高程数据采集于2015年8-9月，在孟加拉国西南部32号圩田（Polder 32）区域的7个测点完成，覆盖一个大小潮周期，采用压力传感器阵列（HOBO记录仪与斯伦贝谢CTD）进行采集。通过扣除大气压并代入9.9 kPa/m的转换系数，将压力值转换为水深。高程数据仅为测点本地值，未统一至共同的垂直基准面。后处理阶段采用平滑样条插值法填补部分仪器在低潮期出露水面时产生的数据空缺。 KML文件展示了圩田建设前、1970年代及2015年三个时期，不同潮汐阶段（最低低潮位、满岸水位及最高高潮位）下水道的平面面积。该数据通过谷歌地球（Google Earth）影像（现代影像）或最早可获取的陆地卫星（Landsat）影像（1970年代数据）进行手动数字化得到。每个多边形要素均包含以下字段：本次研究估算的潮差、平面面积，以及该测点在高低潮之间的蓄水量。结合流量数据，这些空间数据可用于确定单条水道所充泄的潮汐盆地规模。