The news is currently dominated by images of massive flooding in coastal Alabama and the Florida Panhandle as Hurricane Sally made landfall in Gulf Shores with high winds and torrential rains.
Heavy rains and flooding often accompany hurricanes and other storm events. According to NOAA, flooding is the major threat for inland populations. Flash flooding can occur in the blink of an eye due to intense rainfall, often accumulating from some distance away. Flooding along rivers and streams can last for many days after a storm has passed.
Make a flood map
ArcGIS Living Atlas of the World includes authoritative live feeds and other content that helps you learn more about current and predicted flood conditions. Follow these steps to make your own flood map in a minute.
Map Viewer Beta
Step 1 — Sign in to your ArcGIS account. Open Map Viewer Beta, click Add layer, then Browse Living Atlas Layers.
Step 2 — Enter “flood” in search to locate matching layers from the Living Atlas. Scroll down to locate the Live Stream Gauges layer and click (+) to add it to the map. You can also enter “stream gauges” to narrow down the search results.
Tip: To learn more about any layer, click the layer title to View item details.
From the Live Stream Gauges item overview we learn that the layer shows real-time stream gauge readings compiled from a variety of sources. Once added to the map, the legend shows the current flood status.
To simplify the map and focus on stream gauges showing flood conditions, a filter can be applied.
Step 3 — Click Filter in the Settings toolbar on the right. Note there is an existing expression that filters for gauges with recent updates. Click Add expression.
Step 4 — Construct a filter expression as follows:
a – Select Status as the attribute from the list.
b – Select includes as the operator from the dropdown list.
c – Choose the desired values from the dropdown list.
Step 5 — When finished, click Save.
The map shown below is the result of applying the following expression:
Status includes Minor Flood, Major Flood, Moderate Flood.
Click a gauge to view its pop-up for more information.
Map Viewer Classic
Step 1 — Sign in to your account and open Map Viewer, click Add, then Browse Living Atlas Layers.
Step 2 — Enter “flood” in search to locate matching layers from the Living Atlas. Scroll down in the search results to locate the Live Stream Gauges layer and click (+) to add it to the map.
Tip: To learn more about any layer, click the layer title or card to view the item details.
From the item Live Stream Gauges item details we learn that the layer shows near real-time stream gauge compiled from a variety of agencies and organizations. The layer also includes information about the current flow and flood stage and presents information about the source.
Step 3 — Return to search using “flood” and scroll down to locate the National Water Model (Hourly) layer and click (+) to add it to the map.
From the National Water Model (Hourly Forecast) item details we learn that the layer presents a time-enabled model from the National Weather Service that forecasts streamflow volume and velocity for the entire United States. The model predicts the flow in every river reach of the National Hydrography Dataset.
Step 4 — Adjust the layer order to draw the gauges on top of the streams. In Content, grab the Live Stream Gauges layer and drag and drop it above the National Water Model layer.
The flood map
In just a few clicks a map showing current flood conditions and hourly forecasts for streams had been created. The map has been zoomed to the Gulf Coast area where Hurricane Sally’s effects are currently in evidence.
Since the National Water Model (Hourly Forecast) layer is time-enabled, a time slider appears at the bottom of the map. Using the time slider you can (a) play or pause the animation, (b) step forwards or backwards in time intervals, or (c) adjust time settings to set the playback speed, time span, and time display.
Click a stream to identify it and view forecast flow and deviation from normal flow for the time period selected using the time slider.
Click a stream gauge to learn more about the current flow and status. Click More info in the pop-up to view details about the gauging station.
Improve your map
Experiment with different basemaps to see which you like best. You can alter layer transparency and symbols to emphasize the content you want. Add additional layers, such as Recent Weather Radar Imagery, USA Weather Local Storm reports, or USA Weather Watches and Warnings for additional context.
For more information, see:
- ArcGIS Living Atlas website
- ArcGIS Living Atlas Earth Observations content
- View time maps
- Configure time settings
- Map Viewer Beta help (Map Viewer Beta GeoNet Community)
This blog article was originally published on September 17, 2020, and has been updated.