the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Comparing Flood Forecasting and Early Warning Systems in Transboundary River Basins
Abstract. This study compares operational Flood Forecasting and Early Warning Systems (FFEWSs) in transboundary river basins in Northwestern Europe, covering parts of Luxembourg, Germany, the Netherlands and Belgium. This region was hit by an extreme flood event in 2021 with over 200 fatalities. Due to the high death toll, FFEWSs were heavily criticized in the aftermath. Expert interviews from the region revealed strong improvements of the FFEWSs after this flood event in all countries. All regions have invested in probabilistic flood forecasting systems, and all countries now use mobile phone-based alerts. Strong differences in flood warning levels and color codes exist across and within the countries. In response to the 2021 flood, some regions have introduced an additional purple warning level. The interviews also revealed that the uptake of operational impact-based forecasts remains challenging, while these are crucial for translating hydrological forecasts to effective actions. For example, interviewees highlighted the need for operational flood inundation forecasts. However, Flanders is the only region where such forecasts are provided. It is recommended to enhance forecasts with impact-based information, including inundation maps delineating the people and objects at risk. This can improve the early actions taken by first responders and the affected people.
- Preprint
(2213 KB) - Metadata XML
-
Supplement
(265 KB) - BibTeX
- EndNote
Status: open (extended)
- RC1: 'Comment on egusphere-2025-828', Anonymous Referee #1, 17 May 2025 reply
Viewed
HTML | XML | Total | Supplement | BibTeX | EndNote | |
---|---|---|---|---|---|---|
771 | 387 | 17 | 1,175 | 30 | 21 | 34 |
- HTML: 771
- PDF: 387
- XML: 17
- Total: 1,175
- Supplement: 30
- BibTeX: 21
- EndNote: 34
Viewed (geographical distribution)
Country | # | Views | % |
---|
Total: | 0 |
HTML: | 0 |
PDF: | 0 |
XML: | 0 |
- 1
Summary and general comments
This study reviews the status of Flood Forecasting and Early Warning Systems (FFEWSs) in transboundary river basins in the Northwestern Europe Countries that were hit by the July 2021 flood (Germany, Luxembourg, Belgium, and The Netherlands). Following the deadly and costly flood event of 2021, such analyses are essential for improving flood risk management and early warning systems chains, and to foster increased regional cooperation in transboundary river basins.
The study uses semi-structured expert interviews and literature review to analyze and compare FFEWS characteristics in the different countries, including forecast types, warning levels, communication protocols, emergency response plans and institutional coordination. Expert interviews from the region reveal that all systems are under a significant and rapid development after the 2021 flood event, which brought attention to some limitations of the FFEWS at the time. The main findings include the identification of key differences between countries and challenges, especially around harmonization and impact-based forecasting, which is still underused in the region, as only Flanders has operational inundation forecasts. Moreover, the authors find a lack of harmonization in protocols and inconsistencies in warning levels and communication protocols, which hinder cross-border coordination in transboundary river basins.
The paper is well written and contains many interesting details about the FFEWS structure in the four Countries studied, which are of interest for the community and the readers of NHESS.
However, it has some analytical limitations that should be addressed to enhance its clarity (in terms of organization of material and description of methods), rigor (in terms of systematic comparisons), and practical relevance (in terms of enhanced discussion and solid recommendations). In terms of clarity, the organization of the material can be improved as some key information is dispersed and difficult to find (see detailed comments below). A better synthesis should be made to be able to better compare all the key FFEWS characteristics across countries and regions (as further detailed in the comments below). Moreover, the discussion of some developments, limitations and barriers of the current systems should be enhanced, to better connect the analytical review of the FFEWS to the recommendations for their improvement.
Major comments
Table 1 only reports that now all countries have probabilistic hydrological forecasts, but it is unclear when these have been established. It might be beneficial for sake of clarity to have an additional table or scheme, listing or summarizing all the recent developments in FFEWS, or including some information about recent changes in the current Figure 3 or Table 1. The information to highlight and summarize should include: (i) when and how the probabilistic FFEWS were developed (from deterministic to probabilistic or increase in ensemble size?), being this one of the key findings, (ii) when the online platforms were improved, (iii) the emergency response plans were updated, (iv) the communication protocols changed, e.g. national-scale phone-based alerts, etc. This information is only hinted at in different parts of the paper.
Minor comments