This paper has improved a lot. It is much clearer how things are calculated.
However, I still have some difficulties with the calculation of the total sediment budget and the trapping efficiency. Although a major focus of this paper is on this trapping efficiency, this is not discussed properly.
The authors now describe the incoming and outgoing discharge at both the north and south inlet of the study site. But what is done with this information? The inflow in the south seems limited: 16 m³/s when water rises rapidly. So this inflow can be ignored? An estimate of this inflow to illustrate this could be useful. In- and outflow discharge is slightly different. Are there other outlets? Is this within the error of the measurements? No info is given
In and outflow discharges and concentrations are given, so based on this, trapping efficiency can easily be made. Why is this not done and discussed? With 89 m³/s and 26mg/l at inflow, and 86m³/s and 19mg/l at outflow, you get 30% trapping, half of what is in this paper. During peak events, with 191 m³/s and 114 mg/l at inflow and 178 m³/s and 62 mg/l, you get 50%. Would be interesting to discuss this.
The paper refers to the total load of the River Rhine at the German border. Now some additional information is given, but I still wonder how relevant this is. The SSC increases from 15 mg/l at the border to 26 mg/l at the inlet of the site. So on its way to the site, the water clearly changes a lot. Is there a nice correlation for SSC between both sites? During peak discharges, SSC increases 10fold at the German border, but only 5fold at the study site. How are SSC and sediment load at the border and the site correlated? With the provided information, I have strong doubts whether you can use the average 5.8%, calculated for the period July 2014 – March 2015, to the entire study period to calculate the incoming sediment load. Especially given the major peak discharge in 2011. What was the effect of this for the study site? During this event, the total sediment load passing the border was as big as the load of an entire year! |