--- title: "Rising water, counted in metres | Nexus Observatory" description: "A flood map is a sentence about the future: this ground lies below that level. Gauges along the valley, a weather station and a terrain model turn…" url: https://observatory.global/stories/river-floods/ publisher: Nexus Observatory Inc. updated: 2026-10-31 --- [Stories](https://observatory.global/stories/)Place: River basin and floods # Rising water, counted in metres A flood map is a sentence about the future: this ground lies below that level. Gauges along the valley, a weather station and a terrain model turn the sentence into numbers, and the 2030 framework for disaster risk asks for them everywhere1. **Systems**: Water-level gauges, Terrain analysis, Public alerting **Toward 2030**: Early warnings for everyone by 2027 **Figures**: 4, field scene, comparison, systems diagram, timeline to 2030 Go to the references **01** Field scene ## Gauges on a real valley floor. Three water-level gauges sit along the reach, a weather station above it, and an edge node that joins them to a cell site on the valley side. The red isoline is the ground that lies within a few metres of the lowest point of the reach, computed from the terrain. Figure as text: Gauges, weather and edge on a valley drawn from an elevation model A valley drawn from elevation data with three gauges on the floor, a weather station, an edge node and a cell site; a red isoline traces the low ground. - Gauge upstream - Gauge - Gauge downstream - Edge node **02** Comparison ## Two metres, then four. Raise the water two metres above the low point of the reach and the inundated area follows the terrain, not a straight line. Raise it four and the valley floor fills. Choose the scenario and move the divider; the areas are computed from the elevation model, cell by cell. Flood hazard maps of this kind are what European law asks every member state to publish and update2. Figure as text: Ground below the water at two scenarios A split view of the same valley: on the left the ground below two metres above the low point, on the right the ground below a higher level, each traced by a red isoline. **+2 m**: Ground below two metres above the low point of the reach. **+4 m**: Ground below four metres above the low point. **+8 m**: Ground below eight metres above the low point. **03** Systems diagram ## From gauge to warning. A rising gauge is useful only if the warning arrives before the water. Gauges report through a low-power network to the edge, which compares levels with thresholds and issues an alert in the common alerting format3; regional forecasts add days of lead time4. Cut a link to see what still gets through. Figure as text: Flood warning chain from gauges to the public A four-tier diagram: gauges and rain, the low-power gateway and cell site, the edge, and the hydrological service and public alerting. - **Gauges** : Gauge 1, Gauge 2, Gauge 3, Rain gauge - **Links** : LPWAN gateway, Cell site - **Edge** : Edge thresholds - **Warning** : Hydrological service, Public alerts 9 links. Scenarios: Normal operation; Gateway lost to the flood. **04** Timeline to 2030 ## Everyone covered by 2027. The Sendai Framework runs to 2030 and counts early warning coverage among its targets1. The United Nations initiative Early Warnings for All set the end of 2027 for every person on Earth to be protected by an early warning system5. Figure as text: Flood risk and early warning commitments A timeline from 2007 to 2030 with the EU floods directive, the Sendai Framework, Early Warnings for All and its 2027 target. 1. **2007-10** EU floods directive (Directive 2007/60/EC). Hazard and risk maps for every river basin, reviewed every six years. 2 2. **2010-07** Common Alerting Protocol 1.2 (CAP 1.2). One format for alerts across agencies and channels. 3 3. **2015-03** Sendai Framework adopted. Seven global targets for disaster risk reduction by 2030. 1 4. **2022-11** Early Warnings for All launched. An action plan to cover everyone with early warnings. 5 5. **2027-12** Early warnings for everyone. The initiative’s target date. 5 6. **2030** Sendai targets fall due. Including availability of multi-hazard early warning systems. 1 Figure 1 Field scene **Ground within 6 m of the reach low**: 11.28 ha **Gauged reach**: 884 m Figure 1. Gauges, weather and edge on a valley drawn from an elevation model. A valley drawn from elevation data with three gauges on the floor, a weather station, an edge node and a cell site; a red isoline traces the low ground. ## References 1. [Sendai Framework for Disaster Risk Reduction 2015–2030](https://www.undrr.org/publication/sendai-framework-disaster-risk-reduction-2015-2030) . United Nations Office for Disaster Risk Reduction, 2015. 2. [Directive 2007/60/EC on the assessment and management of flood risks](https://eur-lex.europa.eu/eli/dir/2007/60/oj) . Official Journal of the European Union, 2007. 3. [Common Alerting Protocol version 1.2](https://docs.oasis-open.org/emergency/cap/v1.2/CAP-v1.2-os.html) . OASIS, 2010. 4. [Global Flood Awareness System (GloFAS)](https://global-flood.emergency.copernicus.eu) . Copernicus Emergency Management Service, 2024. 5. [Early Warnings for All: Executive Action Plan 2023–2027](https://www.un.org/en/climatechange/early-warnings-for-all) . United Nations and World Meteorological Organization, 2022. ## Related stories [System: Federation across agencies **Many agencies, one picture** No single agency observes everything it needs. 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