Establishing a sediment budget in the newly created “Kleine Noordwaard” wetland area in the Rhine–Meuse delta

van der Deijl, Eveline Christien; van der Perk, Marcel; Middelkoop, Hans

doi:https://doi.org/10.5194/esurf-6-187-2018

Articles | Volume 6, issue 1

https://doi.org/10.5194/esurf-6-187-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/esurf-6-187-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 6, issue 1

Research article

|

07 Mar 2018

Research article |

| 07 Mar 2018

Establishing a sediment budget in the newly created “Kleine Noordwaard” wetland area in the Rhine–Meuse delta

Eveline Christien van der Deijl, Marcel van der Perk, and Hans Middelkoop

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Final revised paper (published on 07 Mar 2018)
Preprint (discussion started on 02 May 2017)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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RC1: 'review', Anonymous Referee #1, 08 Jun 2017
RC2: 'Comments', Anonymous Referee #2, 14 Jul 2017
- AC2: 'response to review 2', Eveline C. van der Deijl, 21 Sep 2017
AC1: 'response to review 1', Eveline C. van der Deijl, 21 Sep 2017

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Eveline C. van der Deijl on behalf of the Authors (21 Sep 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (15 Oct 2017) by Orencio Duran Vinent

RR by Anonymous Referee #1 (27 Oct 2017)

Suggestions for revision or reasons for rejection

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!

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RR by William Kearney (05 Jan 2018)

Suggestions for revision or reasons for rejection

This paper presents a comprehensive analysis of a very good data set from a restored wetland. The revisions have done much to satisfy many of my technical questions, but I have a few minor concerns, most of which are about the clarity with which the methods and results are described.

Pages and line numbers below refer to the version created 17 Nov 2017.

P4L28: Can you describe more thoroughly how this correction was calculated? Which data were used to calculate it?

P5L16: This model needs to be explained more. It was not initially clear to me whether you were using a relationship from the literature or one fit to your data.

I do agree with the first anonymous referee that the high heterogeneity of deposition needs to be accounted for in the estimate of the intertidal sediment budget, but I am concerned that the model does not have a lot of predictive power (R2=0.09), so I am not sure how much you gain from using this estimate versus just using the mean of the measurements. Can you quantify the uncertainty in the model prediction? How does that compare to the standard error of the mean of the measured sedimentation rate in the intertidal area?

P8L19: The value given for the intertidal sedimentation rate here does not match the one given above. It looks like a rounding error.

P8L22: Can you give more detail on how you calculate this future sediment budget? What time scale is this prediction relevant over?

There is some additional analysis (transport capacity and wind wave/shear stress) in the Discussion. The details of the transport capacity calculations, in particular, could be moved to the Results section, while leaving the key conclusion -- "not only the bifurcation, but also the presence of the wide and shallow intertidal area, results in enhanced sedimentation in the centre of the area" -- in the discussion.

The two following statements regarding the transport capacity are unclear to me:

P9L10: "the negative sediment budget of the inlet for the period 2012-2015 can be seen as the total maximum transport capacity of this channel." Why is this true? What is the value of the sediment budget/transport capacity?

P9L13: "the reduced transport capacity of the channels explains only 24% of the positive sediment budget in the centre of the system." I think this means that the reduced capacity of the central channels (54% of whatever the total capacity is) is only 24% of the total sediment budget of the centre of the system. What are these values?

Figure 5: The years on the x-axis are too closely spaced.

Figure 7: I don't understand why the model equation shows two intercept values. Perhaps this could be accounted for in a more detailed explanation of the model as suggested above.

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ED: Publish subject to minor revisions (review by editor) (06 Jan 2018) by Orencio Duran Vinent

AR by Eveline C. van der Deijl on behalf of the Authors (15 Jan 2018) Author's response Manuscript

ED: Publish as is (29 Jan 2018) by Orencio Duran Vinent

ED: Publish as is (30 Jan 2018) by Niels Hovius (Editor)

AR by Eveline C. van der Deijl on behalf of the Authors (31 Jan 2018) Manuscript

Short summary

To study the effectiveness of river delta restoration, we used field observations and elevation data to quantify the magnitude and spatial patterns of aggradation and erosion in a restored wetland in the Rhine-Meuse delta. Erosion and aggradation rates decrease over time, but aggradation compensates for sea-level rise and soil subsidence. Channels in the centre had aggraded, whereas the inlet and outlet eroded. Furthermore, sediment is in general uniformly distributed over the intertidal area.