Technical note: Design flood under hydrological uncertainty

Botto, Anna; Ganora, Daniele; Claps, Pierluigi; Laio, Francesco

doi:https://doi.org/10.5194/hess-21-3353-2017

Articles | Volume 21, issue 7

https://doi.org/10.5194/hess-21-3353-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/hess-21-3353-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 21, issue 7

Technical note

|

06 Jul 2017

Technical note |

| 06 Jul 2017

Technical note: Design flood under hydrological uncertainty

Anna Botto, Daniele Ganora, Pierluigi Claps, and Francesco Laio

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Final revised paper (published on 06 Jul 2017)
Preprint (discussion started on 02 Dec 2016)
Supplement to the preprint

Interactive discussion

Status: closed

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

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RC1: 'Review of “Technical Note: Design flood under hydrological uncertainty”', Anonymous Referee #1, 05 Jan 2017
RC2: 'Review of Botto et al', Alessio Pugliese, 12 Jan 2017
AC1: 'Short reply', Daniele Ganora, 16 Jan 2017
AC2: 'Revised Manuscript and Response to Referees' Comments', Daniele Ganora, 20 Mar 2017

Peer-review completion

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

ED: Publish subject to revisions (further review by Editor and Referees) (07 Feb 2017) by Giuliano Di Baldassarre

AR by Daniele Ganora on behalf of the Authors (20 Mar 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (21 Mar 2017) by Giuliano Di Baldassarre

RR by Anonymous Referee #1 (11 May 2017)

Suggestions for revision or reasons for rejection

The authors have done a good job incorporating the review comments into the manuscript and I feel the content of the manuscript is now acceptable for publication. I do, however, have a number of editorial comments that I hope will help clarify the manuscript further. Therefore, I am recommending acceptance of this manuscript with minor revisions.

p. 1, line 3: The statement is made: “the design flood value is no longer a deterministic value, but should be treated as a random variable itself.” I disagree with this statement. The design flood is treated as a random variable in its estimation; the point is that this component is often ignored when one value is reported for the design flood. This should be revised. Once potential revision could be (in place of lines 2-5): “However, when hydrologic uncertainty is accounted for, the design flood is defined as a range of values.”

Abstract, Paragraph 2: The wording is awkward here and needs to be fixed. It is not that the design flood is “ambiguous” but that, with uncertainty considered, the design flood could be a range of values. The UNCODE procedure uses a numerical cost-benefit approach to capture uncertainty but still result in a single design flood value. The advance of this paper is a simple correction factor that can replace the numerical computations in UNCODE. Paragraph 2 should be revised to reflect these points.

p. 1, line 12: Change “This new design tool” to “UNCODE, when coupled with this simple correction factor provides…”

p. 2, line 13: Replace “for” with “due to”

p. 2, line 15: Add a phase to the end of the statement “the cost-benefit method thus appears as an attractive design approach” since you do not yet explain why this would be the case. Also, for the second part of the sentence, revise to read: “however, due to difficulties in determining the cost and damage functions, it is often unable to be applied.” This sentence is confusing overall and disjointed from the previous paragraph.

Equation 1 and descriptions of c and d: The parameters c and d are still not defined sufficiently. It seems from Equation 1 that they do not change; yet if they are piecewise linear functions, one would expect that they would have subscripts to define the portions of the lines that each slope applies to. Clarify this. Also, add an explicit definition of c and d to the descriptions of equation variables directly after Equation 1.

p. 2, line 32: Delete “these findings through”

p. 3, line 2: The authors note that the framework can be extended “due to the limited data availability” yet there is nothing more mentioned about this. I would delete this statement or expand here. Otherwise, it seems out of place and it is unclear what the authors mean.

p. 3, line 15: Change to read “…approximated and reliable method…”

p. 3, line 19: Revise to read: “…results in a systematically larger value…” and then add a phrase explaining why this is the case.

p. 4, line 3: Coefficients a0, a1, and a2 are still not clearlt defined. Are these the parameters of each of the distributions? I think this is explained in the review response but not in the text.

p. 4, line 5: Instead of call the distributions a “list,” which sounds arbitrary, state that you considered the most common distributions used in flood frequency.

p. 4, line 8: Change “variates” to “values”

p. 4, line 10: Be more precise in your wording. Revise to: “Looking at the properties of the moments of the distribution in L-moment space,…”

p. 4, line 14: Change “fitting” to “fitted” and consider instead of F to signify the sample distribution, to use P_hat, which is the estimate of the parent distribution.

p. 4, line 30: Change to read “distribution results in the best performance in terms of …” and explain why this is the case for PE3.

p. 5, line 13-16: Same comments in general as the abstract. These paragraph needs to be revised. One possible revision to consider: “…analysis provides a solution to the estimate of the design flood when considering the uncertainty in the quantile estimation; however, application…and computationally demanding for the practitioner. An approximate but reliable framework….to easily compute the UNCODE design flood value from the standard value using a correction factor, y_hat.”

p. 5, line 18: Change “standard” to “traditionally-computed” and add “…distributions in flood frequency analysis, they… “

p. 5, line 19: Change “management” to “quantification”

p. 5, line 20: Change “preliminary” to “methods of”

p. 5, line 22-23: Remove the sentence starting with “This implies that…” The point made here is too confusing to the reader and unclear.

p. 5, line 30-31: The statement is made that the values lead to a “reduced UNCODE design flood.” I would caution the authors to make such a general statement that could leader the reader to believe that reduced flood design values have some type of benefit overall. What do the authors intend here in this sentence. Please add text to clarify.

p. 6, line 4: After semicolon, add “therefore”

p. 6, line 6: Delete “all-encompassing”

Supplementary material: Same comment as above when referencing the “list” of distributions considered.

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ED: Publish subject to minor revisions (further review by Editor) (11 May 2017) by Giuliano Di Baldassarre

AR by Daniele Ganora on behalf of the Authors (02 Jun 2017) Author's response Manuscript

ED: Publish as is (07 Jun 2017) by Giuliano Di Baldassarre

AR by Daniele Ganora on behalf of the Authors (08 Jun 2017) Author's response Manuscript

Short summary

The paper provides an easy-to-use implementation of the UNCODE framework, which allows one to estimate the design flood value by directly accounting for sample uncertainty. Other than a design tool, this methodology is also a practical way to quantify the value of data in the design process.