the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 29 Jul 2026
Creating story lines on floods: relating climate-change uplift to (extreme) experienced and future flooding events
Abstract. Fluvial flooding remains one of the most significant climate-related hazards worldwide, with its impacts intensified by increasing urbanisation, land-use change, and climate change. We apply the flood-excess volume (FEV) methodology to analyse major recent flood events on the River Aire in Leeds, UK, and specifically to the 2015 Boxing Day and February 2020 floods, as a basis for evaluating the sufficiency and cost-efficacy of flood defences under current and future climate scenarios. The FEV methodology is used to assess the performance of flood-mitigation measures, integrating engineered interventions and nature-based solutions. Using UK-government climate-uplift guidance, we model how magnitude and frequency of flood events may evolve across future climate time slices. Focusing on the period 2070–2125, our results show that under a foreseen worst-case climate-change uplift of 51 %, the 2020 minor flood event may produce floods with an FEV comparable to that of the major 2015 Boxing Day flood. Such abstract and difficult-to-comprehend climate-change uplift factors are hence clarified by relating two recently experienced flooding events, still fresh in Leeds' citizens' memory, by being able to relate stories of two recent floods of different magnitude. To assess the cost-efficacy and the (in)sufficiency of flood mitigations, we compare the percentage of FEV mitigated with associated costs for future climate-adjusted flood events. Long-term resilience of a future Boxing Day flood worsened by climate-change uplift factors may be insufficient without additional adaptation. We conclude that significant upgrades may thus be required to ensure protection against climate-change enhanced extremes.
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RC1: 'Comment on egusphere-2026-2908', Anonymous Referee #1, 11 Sep 2026
Pullan & Bokhove propose a storyline on floods using two flood events and estimate the future effectiveness of current measures. In doing so, they apply an uplift approach to estimate future hydrographs. They also propose using this information to create storylines to inform citizens.However, several issues prevent me from advising publication:I. The FEV methodology is very appealing, but applying it to two extreme events in a single location does not add insight in terms of interpretability and usability. For such results, authors must report a full qualitative experiment.II. Storylines appear in the title, but they are presented in Appendix B. To reproduce or validate the narrative, the storylines should be annotated, and each key message properly supported, with an explanation of why it is important to communicate.III. The manuscript is not well structured; sections mix methods, definitions, and results; and it contains repetitive or overly long sections.IV. The use of uplifts for two events is not a novel case study or a methodological innovation.I suggest sharpening the paper's focus and using a more standard writing style (even though I must disclose that I am not a native English Speaker). The current version does not include enough information for replication (e.g., how to create storylines) or sufficient contextual information. Moreover, it is unclear where to find the Methods, Results, and Discussion sections.
- As a simple reviewer, I do not know when Boxing Day is. Please keep in mind that your potential readership is global. Also, because two extreme events are used as case studies, you must provide a clear and complete hydrological, hydraulic, risk (i.e., hazards, exposure, vulnerability), and land-use description. Again, do not assume that readers are familiar with how extreme storms behave in time and space in the UK. I recommend including information regarding the annual cycle, detailed precipitation, temperature, and saturation (if available) for days before and after the storms at 15’ resolution. If not available, justify the omission.
- Several paragraphs mix methods, results, and discussion. For instance, in lines 34-47, lines 36-43 could be shortened to 2-3 sentences without losing flow. Move those lines to a dedicated Methodology subsection.
- Avoid using footnotes. Avoid labeling the results from arithmetic operations as equations (e.g., L250). Do not use Wikipedia sources; there are for sure better references. This is not a trust issue, but a matter of using traceable data from agencies or universities.
- The paper’s aim could only be the fourth. The first two apply known methods, while the third one is not replicable or methodologically explained.
- Shorten Section 2
- Section 3.1 could be shortened and converted to a comparative table.
- Figures 4, 6, 8, 9: Put values into comparative tables, add the date, and use the same limits on the horizontal axis.
- Delete Figure 5 and Figure 7.
- Lines 260-264 should be part of the Introduction.
- Sections 4.1 and 4.2 should be shortened. I suggest adding a critical appraisal and moving your conclusion to the Introduction (as in L336-344 and L354-359). Lines 318-330 could be made into a table.
- Section 5 should be a Results subsection. Section 5.1 could be made into a table.
- An opinion on style: captions of tables and figures should be descriptive, but not a repetition of results and discussion that should be (already) in the text body.
- Section 5.2 must be significantly shortened. The sub-subsections are unbalanced in structure and depth. It could be converted into a table. Another option is to relegate it to the Appendices.
- Combine Figures 10, 11, and 12. Use the same scale in a four-panel arrangement.
- Section 5.3 summarizes the results. However, focus on presenting the most salient results. Indeed, L730-750 are a good summary of results that could open the Results section.
- Last but not least, I would like to commend Prof. Bokhove for the chance to read undergraduate work. I also commend N Pullan for taking on the challenge of communicating your work to the community.
- I used a grammar checker for this review. My review and comments come from my own reading and appraisal. I did not use any LLM.
Citation: https://doi.org/10.5194/egusphere-2026-2908-RC1 -
RC2: 'Comment on egusphere-2026-2908', Anonymous Referee #2, 11 Sep 2026
The FEV Methodology proposed in this paper is, in my view, rather interesting as a straightforward modelling protocol for evaluating and communicating the cost-efficacy of different combinations of flood-mitigation measures. I think that the methodology is robust, quite easy to understand and follow. I have a few comments to improve the paper:
1. The title is - to some extent - misleading. In my view, the role of 'storylines' is not as central as the title would suggest. I would recommend revising the title and/or the text accordingly.
2. the FEV methodology is established and already published. I would ask authors to better highlight the value added and element of innovation related to the present work compared to what has been already published. Does it only relate to climate change impact modelling? If this is the case, the paper could look as an 'extension' of a previous work. I think it would be great to better detail the novelty.
3. is the methodology directly replicable elsewhere? what are the requisites? This is particularly true for the estimate of costs, that is notally clear to me. How is it performed? Is it site specific?
4. Concerning the potential evolution of the work, i think it would be interesting not to limitate the analysis to a monetary evaluation as tipically NBS have a lot of 'other' advantages (co-benefits). I would ask the authors to elaborate a bit more on this, as well as on the other potential evolutions of the FEV.
Citation: https://doi.org/10.5194/egusphere-2026-2908-RC2 -
CC1: 'Reply on RC2', Onno Bokhove, 16 Sep 2026
As part of the interim discussion, I give a few selected considerations:
Ad. 3 Unfortunately, the cost-effectiveness analyses tend to be site-specific. These analyses are often very difficult to establish because of a lack of available data, either because the data literally do not exist or otherwise. Given the relative novelty of our approach, such a lack of required data for the square-lake graphs may not come as a surprise? Collectively, we may not be, or are not yet, sufficiently familiar with the particulars needed to establish such square-lake cost-effectiveness analyses? The square-lake graphs can of course only be made after the three-panel FEV graphs have been created so, for the climate-uplifted floods we consider, our costing results build on the new FEV-results. These two results go hand-in-hand.
Ad. 4. (a) One open challenge mentioned in the (original) sections 5 and 6 is the definition of an ensemble of reference hydrographs for the design flood (of a particular chosen return period against which one wishes to seek protection), for varying (spatial-temporal) rainfall and antecedent soil-moisture conditions. See also the (original) figures 11 and 12.(b) A potential evolution of FEV (and associated cost-effectiveness analysis) under climate-change projections is to establish nation-wide applications (e.g., via an online “app”?) in which the work we did here for one river is (partially) automated for a series of river floods across a country, which may be a particularly feasible effort across England. England is mentioned particularly, since we know here that at the government [site https://environment.data.gov.uk/hydrology/landing] (i) flood data and (ii) uplift factors for various regions (and more data) are readily and publicly available, and rating curves can be requested or found at other (public) sites, where appropriate. (Undoubtedly such information is available in other countries as well but --with apologies-- I am not familiar with that.) Acquisition of flood-mitigation information and their costs may be more complicated, see Ad. 3 above. Gathering the stories and experiences of people for one minor and one major flood, with the minor flood becoming similar to the major one under a suitable climate-change uplift factor will also involve some effort, perhaps feasible via citizen science? (Or both may become feasible via advanced “automated” internet searching?) But the first steps of finding these flood pairings and graphing them can be automated via information available from the the government site. The aim here is to establish an open database of scientific story-lines, together with a translation of the science and abstract climate-change uplift factors for the general public via actual stories, i.e., the stories of flood victims. NB Note the distinction between scientific story-lines with its use of graphs, fluid dynamics, mathematics and codes (for which one must somehow have had the training to understand and work with this knowledge and these tools) versus the “stories” on floods experienced and told by flood victims (generally non-scientists). All of this would potentially give everyone access to information on the (potential) impact and potential (partial) mitigation (options) of future floods under climate change, and at a larger collection of locations than only Leeds.
(c) In England, the provided uplift factors calculated and provided may be based on underlying ensemble calculations under varying rainfall and moisture conditions including the subsequent flood predictions for various rivers? The (design) ensemble we seek could be a subset of the ensemble of calculations used to establish the nation-wide uplift factors? That could mean that the underlying calculations for these uplift factors already contain the information to establish the (design) ensemble in the challenge under (a)? That would mean that the FEV and square-lake graph analysis can evolve further. Otherwise more advanced calculations need to be established. Combine this with the evolution under (b) and one has or could have a further potential advance of the FEV-analysis. I am in the process of collecting further information on whether the underlying calculations of the uplift factors contain valuable information on the required ensemble under (a), or not.
All of the above, under Ad. 4, concerns potential options for future research well beyond the presented diagnostic work. At the moment, we are not intending to include most of the above considerations in the anticipated revised manuscript (as they are a bit too speculative). –-Co-author OB.
Citation: https://doi.org/10.5194/egusphere-2026-2908-CC1
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CC1: 'Reply on RC2', Onno Bokhove, 16 Sep 2026
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