Map & Layers

The map

• River gauges: Colored pins are used to indicate river gauges on the map. Gauges mark points along rivers where water levels are monitored. These can be physical or virtual gauges based on models. A side panel with additional information about a gauge can be opened by clicking on the pin.
• Zoomed-out view: In the zoomed out view, gauges are aggregated in hexagons.

Search bar

• The search bar can be used to find a specific location. The map will then zoom in, and a side panel with information about that place will open.

View options

The view options menu allows you to understand the information on the map and customize what you see. 

• Understand the gauges:

  • Gauge legend: See the meaning of the pin colors, which show different flood risk levels (more details below).
  • Additional coverage: Choose to see data from gauges with lower confidence levels. These gauges aren't shown by default because their readings may be less certain. Toggling this option switches between a view with higher-confidence gauges and a view with lower-confidence gauges (more details below).

• Explore the different layers:

  • Inundation probability: View a map showing the current or future probability of flooding in different areas (more details below).
  • Inundation history: the past occurrence of flooding in different areas (more details below).

You can toggle the Inundation probability, inundation history, and additional coverage on or off to see the information most important to you.

Additional coverage

While all forecasts in the Flood Hub are generated by Google's flood forecasting model, for some gauges, quality assessment was not satisfying. This means that either the data necessary for evaluation was unavailable, or the evaluation did not produce sufficiently high metrics. By default, only gauges with Higher-confidence are shown on the map. The "Additional coverage" option let you switch to gauges with Lower-confidence, enabling you to select between a smaller set of high-confidence gauges or a larger set of lower-confidence gauges.

• Higher-confidence - Locations where the quality assessment of the model was possible and yielded high metrics. The evaluation is based on historical streamflow observations, or on satellite imagery.
• Lower-confidence - Locations where quality assessment was not possible due to lack of data necessary for evaluation, or the evaluation did not produce sufficiently high metrics. Note that in most cases this is the same hydrologic model which is used.

Please use the Flood Hub Virtual Gauges Information with caution, you should not use this information as a sole source of data as actual flood conditions may vary.

Gauge legend (pin colors)

• Extreme: Highest flood risk
• Danger: High flood risk (expected roughly every 5 years)
• Warning: Moderate flood risk (expected roughly every 2 years)
• Normal: Low flood risk
• No data: No information available

Layers

Inundation probability

Inundation probability show the areas likely to be underwater during a flood, with darker blues indicating a higher chance of flooding. Inundation probability maps are not supported for all gauges (in some cases, the inundation model do not show clear and regular inundation patterns. In these regions we decide to only share the hydrologic information). For each gauge, you can refer to the Gauge panel's additional information section to find more information about Inundation probability for this gauge (see Gauge side panel)

Accuracy: Predictions are made at a 15-meter resolution.

Inundation history 

• What it shows: This layer shows how often different areas were experiencing negative impact from water in the past. It helps identify places at higher risk of inundation based on historical records.
• How it works: For each pixel, the color depends on the percentage of the time the pixel was under the water during the past time period. The darker the color, the more often that area was flooded.
• Important notes:
  • This map shows how often an area was under the water, not how deep the water was.
  • Past flooding doesn't guarantee future flooding. While this map shows historical trends, actual flooding depends on the specific circumstances of each event.
  • Areas that are not covered by any of the layers can still be flooded in extreme events.

  • This layer has limited availability. While it covers a majority of the regions, it is restricted to the following latitudes and longitudes:

    • Minimum latitude: -39.0
    • Minimum longitude: -125.0
    • Maximum latitude: 43.0
    • Maximum longitude: 170.0

  • Due to these limitations, the layer does not extend to the extreme northern or southern points.