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This The following is a description of GloFAS v4.0, available as pre-release on the GloFAS Stage Platform from 05 July 2023 and fully operational GloFAS from 26 July 2023.

v3.4. For an overview of other GloFAS releases, please see : GloFAS versioning systemThe forecasts of GloFAS version 3.4 are available in pre-release mode from 16 November 2022 on the GloFAS Stage Platform: https://stage.globalfloods.eu/glofas-forecasting/. To access the GloFAS stage website, visit https://stage.globalfloods.eu/accounts/signup/ to create your account.

Summary

GloFAS version 3v4.4 introduces some important enhancements 0 introduces a number of major changes to the web productssystem, including methodological, visual, and technical changes. The changes aim to aid user experience when interpreting the forecasts on the GloFAS map viewer. All changes implemented are summarised here:

STATIC tab

• The 'Upstream Area' static layer has been replaced by the 'LISFLOOD Drainage Network'. This layer now shows the rivers as vectors, with the thickness and colour of the lines indicating the drainage (or upstream) area.

HYDROLOGICAL tab

• 'Flood summary for days 1-3', 'Flood summary for days 4-10', 'Flood summary for days 11-30':
  • Flood summary maps are coloured according to the probabilities of exceeding 2- (yellow), 5- (red), and 20-year (purple) return period flood threshold within the given period, with the colour tone defined according to three probability of exceedance classes (30-50%, 50-75% and 75-100%).
• New 'Flood summary for days 1-30' layer, showing the flood summary over the full 30-day forecast horizon.
• '5 Year Return Period Exceedance' and '20 Year Return Period Exceedance'
  • Colour tone defined according to six probability of exceedance classes, defined by increments of 20% (instead of increments of 10%) to improve visibility.
• Major upgrade of the methodology used to generate the 'Reporting Point' layer :
  • Improved algorithm to generate the dynamic reporting points, resulting in more homogeneous coverage of the flooded river sections by the reporting points.
  • Dynamic reporting points remaining at the same location over consecutive forecasts and only removed when the flood signal disappears, allowing the user to trace the evolution of the forecast over the same river catchment.
  • Reporting point colours now only show the flood severity category (yellow, red or purple). This improves visibility and avoids the repetition of information already provided in the flood summary maps with the three probability-based subcategories.
  • Peak timing indicated on the reporting points as black border (within first 3 days) or greyed colours (beyond 10 days). This allows to quickly identify areas with flood expected in a short range (i.e. requiring more immediate action), or floods expected in more than 10 days.
  • Forecast tendency and peak date algorithms are defined according to the ensemble median, consistently with the reporting point flood categories, with a downward tendency highlighted if the discharge drops by at least 10% compared with the reference initial discharge value.
  • Discharge hydrograph vertical axis scale is defined according to the interquartile range of the ensemble forecast. This change avoids outliers dominating the hydrograph plots, thus improving visibility of the forecast especially in very dry areas. Maximum ensemble forecast values shown as a numerical value if they fall outside of the displayed range.
  • Forecast overview table simplified to show the combined flood signal of the three severity levels (2-, 5-, and 20-year), colour-coded according to the flood summary maps probability levels.

FLOOD RISK tab

• Upgraded methodology used to generate the 'Rapid Flood Mapping' layer 
  • Flood extent defined according to the probability of exceedance of the ensemble median (instead of the ensemble mean), consistently with the way flood severity is defined in the reporting points.

Map viewer features:

• Multi-tab feature which allows users to see pop-out windows for several queryable products in a single window.
• Improved functionalities in the pop-out windows for better user experience (dragging, closing and resizing).
• Revised web layer legends.
• Introduction of a stage Information System open to all following registration so that users can access new developments ahead of a release for monitoring.

Wiki

• Updated GloFAS -IS products documentation on the GloFAS wiki.

:

• higher spatial resolution. GloFAS v4.0 has 0.05 degrees resolution (~5km), as opposed to all the previous GloFAS versions having 0.1 degrees resolution (~10km).
• an entirely new set of 0.05 degrees resolution input maps produced using the most recent research findings, remote sensing, and in-situ datasets.
• major improvements to the open-source hydrological model LISFLOOD.
• a new hydrological model calibration at 1995 in-situ gauging stations. Furthermore, a parameter regionalisation was performed to estimate the parameters of catchments for which in situ discharge observations were not available.
• new return period thresholds and snow water/soil moisture anomaly maps based on a climatology from 1980 – 2022. The GloFAS v4 river discharge climatology is available at the C3S Climate Data Store.
• updated GloFAS Seasonal forecasts using the newly calibrated, higher resolution hydrological model.
• Increased spatial resolution from 1km to ~90m (3 arc secs) for the flood hazard maps used in the GloFAS rapid flood mapping and impact assessment

This major version change is associated with an update of the historical hydrological reanalysis. 

This upgrade of GloFAS has large impacts on the GloFAS modelling results.

31 stations were also added to the reporting point: 9 stations in Canada, 7 stations in Russia, 4 stations in Finland, 3 stations in Argentina and 1 station in each of Brazil, United States, Morocco, Benin, Uganda, Thailand, Columbia and South AfricaThis upgrade of GloFAS does not impact on the GloFAS modelling and data production/availability.

Technical details