Flood Early Warning System

What is it?

Flooding from extreme rainstorms can cause safety concerns and property damage. To help with emergency response efforts and to keep people safe, we launched the Flood Early Warning System (FEWS) that predicts severe weather and helps the city prepare for flooding.

Benefits

Predict flooding along Raleigh’s creeks.
Notify City Leaders, Emergency Management, and the public of potential flooding.
Close roads (as needed) sooner.

How it Works

We're focused on collecting data and using technology to determine:

When streams may flood;
How high floodwaters may get;
How much lead time we have to prepare; and,
What resources are needed.

Data Used
Stream and rain gauges	Gauge-Adjusted Radar Rainfall (GARR) (Provides real-time data on rainfall amounts across Raleigh)
Soil saturation	Infiltration rates
Weather Forecasts	Subsurface runoff
Drainage network	Soil moisture
Watershed properties	Reservoir information

The dashboard that provides data from the system is for city staff only. You can use this map to track storms with us.

Software and Dashboard

Check out some of the key system components and capabilities of our FEWS. We are partnered with Wake County, Raleigh National Weather Service, US Geological Survey (USGS), and the US Army Corps of Engineers to provide access to Raleigh's FEWS:

Rainfall Forecasts: Forecast future rainfall over the next hour, 18 hours, 3 days, and 7 days.
Stream Gage and Rainfall Data: Raleigh partners with the USGS to install, operate, and maintain a network of stream gages located throughout the Crabtree Creek and Walnut Creek watersheds. This information is used for real-time rainfall and flood level reporting and calibrate flood models.
Gauge Adjusted Radar Rainfall (GARR): Provides rainfall depths every five minutes across City of Raleigh/Wake County service area for each one-by-one square kilometer pixel. This data is supplemented and calibrated with a network of physical rain gages across the region.
Flood Prediction Modeling: Provides graphs of each stream gauge location with past and current stream observation levels and a prediction of the future stream level and flood elevation timing into the future based on modeled rainfall forecasts.
Alerts Manager: - An alerts function for Raleigh staff with access to the system on available system data such as: Forecast Rainfall, Gauge Adjusted Radar Rainfall Amounts, Stream Gauge Levels, Predictions, Depth Duration Frequencies, and more.
"What If" Scenarios: The system also has the ability for us to run rainfall scenarios through the systems flood model and provide us a look at what might happen across the city during those flood events. It also has the ability for use to pull in the rainfall forecasts that are in our Rainfall Forecast app to see what potential flooding a predicted storm might cause.

Other Key Components

Flood Monitoring Cameras

We use an extensive network of cameras to monitor flooding throughout the system. These cameras are installed and maintained in partnership with our Department of Transportation. We also have access to another 200 transportation cameras and 20 solar-powered, cellular networked video cameras. Learn more about theses cameras and how they support these efforts.

Flood Warning Sign Systems

Raleigh has nine locations that have flood warning sign systems installed in flood prone areas. These signs activate and start flashing for motorist to see when the flo sensor in that area is activated. These signs are installed and maintained in partnership with RDOT. More information can be found here:

Active Flood Control System (Lake Johnson / Walnut Creek)

Our Stormwater team has a monitoring and real-time control system installed at Lake Johnson that allows us to monitor the lake level and control the valve and gate at the tower remotely. We use this system to proactively lower the lake prior to larger know storm events to reduce the risk of flooding along Walnut Creek.

Severe Weather Preparedness

It is our responsibility to help educate the community on how to best prepare for flooding and other severe weather-related events. Our website has a lot of helpful information on this topic.

Track Storms with Us

You can use the city website to track flood levels at key locations in the Crabtree Creek and Walnut Creek watersheds including links to the USGS webpage with more details of flood elevations in real time.

Collection Times

A US Geological Survey stream gauge near Walnut Creek — A stream gauge on S. State Street.

In coordination with USGS, as of the Summer of 2022 we now collect and transmit gauge data every five minutes at all our stream and rain gauge locations (instead of every fifteen minutes or every hour as in years past).

Note: The current gauge data is not available right away. There is a brief processing period from when data is collected to when it's available on the USGS website or our dashboard.

Process

We are working on this program with consultant, Vieux and Associates. The process includes:

Getting details on floodprone areas;
Identifying types of warning alerts;
Recommending flood forecasting for 'hotspot' areas;
Gathering data and modeling stream flow and flooding;
Inventorying and mapping the stormwater system; and,
Setting up, maintaining, and expanding the early warning system to track flooding conditions.