DOI: 10.25405/data.ncl.26282620
title: Hydrodynamics along embankment edges of Kumirmari island, Indian GBM delta.

description: Hydrodynamics measured at the base of embankments and foreshores at three locations around Kumirmari island, Indian GBM delta. The purpose of the survey was to determine the level of hydrological forcing around the island, to provide guidance on coastal flood and erosion protection planning. Tidal inundation, current velocity, and wave orbital velocity were measured using B4+ Mini Buoys (low-cost bottom mounted floats). Wave heights and energy were measured using RBRSolo<sup>3</sup> D | wave sensors. Water depth in front of embankments were measured using a Garmin Aquamap device. Sediment properties were also gathered at each hydrodynamic sensor deployment.<b>Data collection method:</b> Data to assess erosion and flood risk along Kumirmari island, Indian GBM delta, was gathered at eastern (22°12′43″N , 088°57′20″E), southern (22°10′40″N , 088°55′55″E), and western (22°12′15″N , 088°54′50″E) sites.<br><i>Acceleration</i>B4+ Mini Buoys were deployed at the base of embankments and at the bottom of fronting intertidal habitat. Each logger sampled y-axis acceleration at 1 Hz. Unfortunately, some Mini Buoys were lost during deployment.<br><i>Wave parameters</i>An RBRSolo<sup>3</sup> D | wave sensor was deployed at the bottom of fronting intertidal habitat at each site along Kumirmari. Height of the RBRSolo pressure sensor above the bed was 4-5 cm. Velocities were recorded at a rate of 16 Hz in 17-minute bursts continuously. Atmospheric pressure, water density, sensor altitude (height), temperature, conductivity, salinity, and the specific conductivity coefficient were set to 10.1325 dbar, 1.0281 Mg/m³, 0.1 m, 0°C, 42.9140 mS/cm, 35 g/kg, and 0 respectively. ‘Wave’ default settings were used.<br><i>Water depth</i>A Garmin Aquamap 100S mounted to a boat measured channel depths at regular intervals along southern and western locations using a Garmin sounder module and transducer. No data was gathered at the eastern location due to poor weather.<br><i>Soil parameters</i>Soil organic matter content, conductivity (diluted in deionised water at a soil-water ratio of 1:2.5) at 25°C, moisture content, bulk density, and grain size (classified as percentage of sand, silt, and clay) were measured using IS 2720 (part 22), IS 14767, IS 2720 (part 2), IS 2720 (part 8), sieving standards respectively.<br><i>Coordinates</i>Coordinates were taken using Google Maps on an iPhone 13 Mini. Coordinates are expressed in WGS84 standard.Data collected between:14/07/2022 and 01/08/2022<b>Data processing:</b> Mean and standard deviation in acceleration were calculated across 1- and 10-minute moving windows respectively. These were then used to assign inundation status (emersed (N), partially inundated (P), or fully submerged (F)) using a calibrated Quadratic Discriminant Analysis model, and current and wave orbital velocities from calibration curves (Ladd et al. 2024). Soil conductivity was converted to salinity using the ‘ec2pss’ package in R.No processing was done to the wave parameter, water depth, or coordinate data.<b>Related blogs/publications</b>https://livingdeltas.org/resources/hydrodynamics-survey-along-embankments-of-kumirmari-island-gosaba-indian-sundarbanhttps://livingdeltas.org/news-and-events/the-hub-presents-report-to-the-government-of-west-bengalhttps://livingdeltas.org/news-and-events/delta-digest-newsletter-june-004