Erosion experiments with homogenized cohesive sediment samples from the Port of Hamburg - Erosion rates and erosion thresholds

The data set was collected within the context of the research project ELMOD - “Simulation and analysis of the hydrological and morphological development of the Tidal Elbe for the period from 2013 to 2018”.

In total, 34 erosion experiments have been conducted with homogenized cohesive sediment samples collected at two sites in the Port of Hamburg. The samples have been diluted to specific densities between 1050 - 1250 kg/m³ for the experiments.
During the erosion experiments, a maximum of 13 loadsteps with a duration of 15 minutes each and bed shear stresses between 0.03 - 0.40 N/m² has been applied.
The experimental procedure and the utilized erosion device (C-GEMS) are describe in detail in Witt et al, 2024 (https://doi.org/10.3389/fmars.2024.1386081).

The data set consists of:
1. The (raw) experimental data collected in 34 erosion experiments with cohesive sediment samples from two locations in the Port of Hamburg (Norderelbe (NE) and Suederelbe (SE), see Witt et al, 2024).
2. The erosion thresholds (TauC) derived from the experimental data, following the methodology presented in Witt et al, 2024 (SSC-method).
3. The Python-Code used to derive the erosion thresholds from the raw data.
4. The grain size distribution (GSD) of the sediment samples from location NE and SE.
5. Visualizations of i) exemplary evolutions of the suspended sediment concentration (SSC) and erosion rates (ER) measured in selected experiments and ii) the derived erosion thresholds vs. the bulk density of the sediment samples for all experiments.

Additional information:
To 1: The files Experiments_raw_(NE).csv and Experiments_raw_(SE).csv contain the raw SSC-data of the experiments. During the experiments with the C-GEMS, the SSC was recorded in a frequency of 0.2 Hz by a Hach Solitax sc probe.
The background SSC (measured before the start of each experiment) has already been substracted from the values included in the files, thus the values describe the increase in SSC in relation to the beginning of the experiments.
Column "Time [s]" is the experimental duration, "Tau [N/m²]" is the nominal applied bed shear stress (*,more information below) and e.g. column "NE1-2_3-1100" contains the SSC-data (in mg/l) for one experiment with sediment from site NE and a homogeneous density of 1100 kg/m³.
The term NE1-2_3 describes the exact sediment sample used for all experiments from site NE (the same applies for SE accordingly). The number in brackets following the described nomenclature, describes the number of the repetition experiment.
For sediments from site SE densities from 1050 kg/m³ to 1200 kg/m³ and for sediments from site NE densities from 1100 kg/m³ to 1250 kg/m³ have been tested. The intervall between the tested desities was 25 kg/m³ each.
For each tested density at least two repetitions have been conducted. For single experiments with sediment from site NE more repetitions have been carried out (up to 7).
The water used for the experiments was site specific water collected in the Elbe. More information in Witt et al, 2024.

*Two setups of the C-GEMS were used. For setup 2 the nominal applied bed shear stress has to be multiplied by the factor of 1.22. This applies to all experiments with repitition number "(2)" and additionally experiments NE1-2_3-1150 (4) and NE1-2_3-1150 (6).
The relationship described above has already been taken into account in the further analyses and provided python-code.

To 2: The files TauC_(NE).csv and TauC_(SE).csv contain the erosion threshold for each experiment derived by applying the SSC-method presented in Witt et al, 2024.
Column "Density [kg/m³]" describes the density of the tested sample, column "TauC [N/m²]" the derived erosion threshold and "R^2" the coefficient of determination derived from the log-log regression of loadstep averaged SSC (see Witt et al, 2024).

To 3: The files Calculation_TauC_SSC_(NE).py and Calculation_TauC_SSC_(SE).py contain the python-code, which was used for post-processing of the raw-data and calculation of the erosion thresholds. Python version 3.12.3 was used.
The files need to be executed in the same folder as the respective raw-data file (or the path has to be adjusted in the code accordingly). If needed (e.g. for visualization), also files with moving-averages (60s) of the measured SSC and ER or load-step averaged values for SSC and ER can be written to separate files.
To do so, the resp. lines in the code need to be un-commented.

To 4: Files GSD_NE.txt and GSD_SE.txt contain information on the grain size distribution of the sediment samples from sites NE and SE. The GSD were derived by a combined hydrometer and sieve analysis.

To 5: File Examples_SSC_ER_evolutions_(SE+NE).jpeg gives an impression of the results of the erosion experiments in terms of the SSC and ER evolutions for selected experiments with samples from both NE and SE site.
File Visualization_Erosion_Threshold_(SE+NE).png visualizes the derived erosion thresholds for experiments with samples from both sites.