Sustainable risk management of trouble spots caused by heavy rainfall events: Citizen Science app and data analytics for residents and authorities

Hoffmann, Jaqueline; Nau, Sascha; Abler, Sabrina; Theis, Vincent; Fischer-Stabel, Peter; Janßen, Julian; Abecker, Andreas

doi:https://doi.org/10.5194/egusphere-2025-3702

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https://doi.org/10.5194/egusphere-2025-3702

Preprints

28 Aug 2025

| 28 Aug 2025

Status: this preprint is open for discussion and under review for Natural Hazards and Earth System Sciences (NHESS).

Sustainable risk management of trouble spots caused by heavy rainfall events: Citizen Science app and data analytics for residents and authorities

Jaqueline Hoffmann, Sascha Nau, Sabrina Abler, Vincent Theis, Peter Fischer-Stabel, Julian Janßen, and Andreas Abecker

Abstract. To address the increasing threat of heavy rainfall events the FloReST (Urban Flood Resilience – Smart Tools) project focuses on the identification and prediction of emergency flow paths in urban areas and enhancing risk management and communication. The project developed a Citizen Science app to document and report pluvial flood risks in urban areas due to the fact that conventional flood protection has so far focused mainly on fluvial hazards. The population is involved in sustainable risk minimisation through the active use of the app and local risk awareness. Additionally, the app includes educational functions through a user guidance on categorizing pluvial hazards and taking preventive measures. The app is complemented by a Geo Data Warehouse, which enables authorities to analyse and visualise the data transmitted by users via customisable dashboards. Although there are still some technical limitations, such as limited offline functionality and inaccuracies in the use of Global Navigation Satellite Systems, these may be addressed in future research. Thanks to its open-source design, the system remains scalable and can be adapted to other regions worldwide. Overall, the Citizen Science app and Geo Data Warehouse form an innovative, participatory tool that improves the resilience of cities to climate change through inclusive, data-driven risk management.

Received: 07 Aug 2025 – Discussion started: 28 Aug 2025

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Jaqueline Hoffmann, Sascha Nau, Sabrina Abler, Vincent Theis, Peter Fischer-Stabel, Julian Janßen, and Andreas Abecker

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'Comment on egusphere-2025-3702', Jonathan Paul, 05 Sep 2025 reply
REVIEW OF egusphere-2025-3702 (NHESS)

“SUSTAINABLE RISK MANAGEMENT OF TROUBLE SPOTS CAUSED BY HEAVY RAINFALL EVENTS: CITIZEN SCIENCE APP AND DATA ANALYTICS FOR RESIDENTS AND AUTHORITIES” BY HOFFMANN ET AL.

This manuscript details the development of a novel app in the realm of risk management of pluvial floods. While the topic is interesting and the paper generally very well written, I have several major concerns about the narrative: this is a proof-of-concept descriptive paper that employs citizen science (CS) almost as an add-on. I would suggest either greatly enhancing the CS aspect through actual user testing, in the field, with a variety of different stakeholders (including local government and risk managers, who seem to be the intended target audience) or excising the CS part and focusing solely on the computational side of app development. Three of the five figures are simply screenshots of various aspects of the app. In general, the literature review misses several key papers on CS and the development of apps / new tech to that end, and instead features a strong regional focus. Citizen (or community) science must not be seen as a universal panacea; likewise the development of apps has a long documented history of failure, which must be acknowledged. Several recent studies (extensive reference list provided below) have noted a movement away from ad hoc apps, which may not continue to be used successfully by local stakeholders, instead piggybacking on existing social media and platforms like WhatsApp and OpenStreetMap. Finally, it is correctly stated that CS can play a role in democratising science, and that the app will be tailored to local communities. This is contradicted by having the app solely in the German language: either it must be made clear that the app is of sole relevance to Germany, or some form of language flexibility could be introduced.

MAJOR COMMENTS
I feel the manuscript would work better if it was agnostic to the specific research project i.e. omit all mention of FloReST except for the acknowledgements, and couch the content instead on risk management of heavy rainfall events. At the moment it reads like an introduction to FloReST (e.g. Lines 212–4; 485–6)

The literature cited and Section 1 has a heavy German bias. I would suggest either noting down the regional focus in the title, or amending the Introduction to make it more general/global e.g. on Line 26, there is a big jump in the narrative from a general statement on climate change exacerbating pluvial flood events (on which note, the second sentence would benefit from additional citations and/or quantification) to the Ahr Valley floods, which will not immediately be familiar to the broad NHESS readership. I also suggest citing Rhein and Kreibich (2025) at this point - https://nhess.copernicus.org/articles/25/581/2025/

Several sections in the manuscript need more (or better) citations to back up statements made. For instance:

Lines 27–28: “… continuous research is being conducted …”

Paragraph starting on Line 34 (“Risk management includes …”) – particularly statements asserting that “valuable knowledge often resides with residents …” about local/indigenous knowledge

Line 63: “fluvial events, which are usually easy to predict …” – really? Relative to pluvial or groundwater flooding?

Line 80: “Risk management therefore has both an educational task …”

Line 82: Assertations about the poor predictability of pluvial events

Line 92: “Currently there is often a gap …”

Line 129: “The most common method of CS is the questionnaire” – not sure that this is actually true.

Section 2.3 – missing some important watery citizen science programs and initiatives, e.g. CrowdWater – see their website https://crowdwater.ch/en/start/ - they have also published plenty of articles.

Line 143 – on specific tailoring of apps to local communities. There is an entire literature on this, and knowledge co-production using apps, the Internet of Things etc (see Turner 2021 for one example - https://www.tandfonline.com/doi/full/10.1080/02615479.2020.1762858)

I suggest that Sections 1 and 2 be merged, as the narrative (as it stands) jumps around significantly, with citizen science being introduced briefly in the Introduction, before a more detailed consideration in Section 2.

Citizen science needs a far more careful treatment. For instance, Bonn et al. (2002) is not an appropriate reference to back up the introductory statement of Section 2.2; you might want to have a look at Cohn (2008) or Irwin (1995) instead (full details below). Also – I am really not a fan of reviewers who ask authors to include a load of self-citations, but I would suggest at least glancing through Paul et al. (2018), which gives a flavour of many challenges and tradeoffs when utilising a citizen science framework in geohazard risk reduction / resilience building. There are also several papers that consider the utility of apps that might be consulted – look at the references within Paul et al. (2021) for starters.

Two additions would greatly strengthen the citizen science discussion: (a) some mention of the need for apps to be “useful, useable, and used”, and steps that were / could be taken to ensure this; (b) more detail on the mechanics of citizen science projects, even down to potentially replacing “citizen” with “community” (see Ballard et al. 2024 - https://www.tandfonline.com/doi/full/10.1080/13504622.2024.2348702) – but also how participant motivation was dealt with, what incentives might have been needed, and steps that were taken to enhance project sustainability/legacy

Line 103 – needs some acknowledgement that citizen science data are often criticised by the scientific community for its lack of accuracy and simplicity. This is another part of the manuscript that would benefit from blending with the corresponding part of Section 1. On a related note: on Line 102 (“The CS approach is a win-win situation …”) – no! There is no recognition of the various negative externalities that can result from CS projects, such as lost community trust if results are not immediately forthcoming, or inaccurate / imprecise data, or zero data production altogether.

Line 108 – this is in Germany? Are there any comparable global statistics?

Can you strengthen the end of Section 2.2? Rather than including a saying or anecdote, why not instead discuss the importance of the polycentric governance of risk, starting from Elinor Ostrom’s suggestions (summarised here - https://onlinelibrary.wiley.com/doi/full/10.1111/psj.12518)

The overall concept is sound but it must be made clearer that the proposal is purely a proof-of-concept. The final paragraph of Section 2 (“… opens the possibility for various municipalities to use the project …”) is very (over?)-optimistic and elides the significant technical, political, and regulatory challenges that might stand in the way of this level of operationalisation.

3–5 are just screenshots of the app? Might it not be preferable to include an additional schematic diagram of its intended operation and use?

MINOR COMMENTS
Line 14 – remove “a” before “user guidance”

Line 36 – remove “a” before “runoff”

Line 78: The level of education … is (not are)

Line 85: be developed (not are)

Line 86: be improved (not is)

Line 148: “a new software will be programmed as CS project” – this is unclear

1: Map display (not displan)

Line 239: “sustainable risk management in heavy rain prevention” – this is a little unclear; rain can’t be prevented

REFERENCES
Cohn JP. Citizen science: can volunteers do real research? Bioscience 2008, 58: 192.

Irwin A. Citizen Science: A Study of People, Expertise and Sustainable Development. Abingdon, UK: Psychology Press; 1995.

Paul J.D., W. Buytaert, S. Allen, J.A. Ballesteros-Canovas, J. Bhusal, K. Cieslik, J. Clark, S. Dugar, D.M. Hannah, M. Stoffel, A. Dewulf. M.R. Dhital, W. Liu, J.L. Nayaval, B. Neupane, A. Schiller, P.J. Smith and R. Supper, 2018. Citizen science for hydrological risk reduction and resilience building. Wiley Interdisciplinary Reviews: Water, 5, e1262

Paul J.D., E. Bee, and M. Budimir, 2021. Mobile phone technologies for disaster risk reduction. Climate Risk Management, 32, 100296

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Jonathan Paul
Royal Holloway, University of London
5 September 2025

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Citation: https://doi.org/10.5194/egusphere-2025-3702-RC1

Jaqueline Hoffmann, Sascha Nau, Sabrina Abler, Vincent Theis, Peter Fischer-Stabel, Julian Janßen, and Andreas Abecker

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Short summary

The FloReST project identifies emergency runoff drains in cities to develop tools for disaster prevention during heavy rainfall. Pluvial flooding can occur rapidly and far from rivers, often due to non-functional drains. A citizen science app will gather local knowledge, raise awareness, and support education. Data will be stored in a geo data warehouse. Together, the app and warehouse form an innovative, inclusive tool to boost urban resilience to climate change.


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