A riser structure in the middle of Lake Johnson to lower water levels

Lowering Water Levels

Managing a high-hazard dam from our office


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Checking the Lake Lower Water Levels Benefits Video: Behind the Scenes - Lowering Water Levels

This pilot program uses a camera and online system to help prepare for flooding from a major storm, like a hurricane. We now automatically lower water levels in the dam at Lake Johnson and can respond more quickly when a big storm is headed our way. We do this to keep people safe and reduce flooding impacts downstream. 

Why this matters. We control the flow of water by lowering water levels in the lake. This means that when we lower levels before a storm using a valve, less water will flow out of the dam downstream because there is more room for the lake to fill back up during a storm. 

A high-hazard dam – high risk for people living downstream if the dam fails and causes flooding. We designed the dam at Lake Johnson so that water flows over the dam into Walnut Creek. These new features help protect you from the water flow and preserve the lake.

Checking the Lake

We use a camera to track the lake’s water level and storm flows in real time. We can see when we need to:

  1. Safely open the valves at the dam and lower water levels to limit impacts from flooding;
  2. Make sure water isn’t leaving the dam too fast (only two feet per day); and,
  3. Fix issues with water flow that could impact residents downstream.

The camera takes a photo every five minutes (Images aren’t recorded/saved). You can see what we see on the US Geological Survey’s website.

We start monitoring a storm and lowering water levels about 6-8 hours prior to when the storm is forecasted (when possible). This gives water time to safely flow out of the lake. We also close the valves before the storm reaches our area so that excess water does not flow downstream. 

Lower Water Levels

Before the pilot program, we manually lowered water levels at Lake Johnson. This included taking a boat to the structure in the lake and turning the wheel to open the valves for the dam spillway. Doing this was unsafe. The structure’s ladder is slippery during bad weather and covered in algae from the water.

Now, we can open the valves and lower water levels right from our office keeping you and our staff safe in the process. (In the future, an alarm will sound when the lake water is being lowered.)

Benefits

More efficient.
It used to take up to a day for staff to open the valves and lower water levels at a lake. Now, we can respond and open the valves within minutes.

More prepared.
We see conditions in real time and notify first responders sooner to prepare for flooding.

More focused on the environment.
We control the flow of water to protect the shorelines of the lake.

Video: Behind the Scenes - Lowering Water Levels

Lowering Water Levels at Lake Johnson From The Office

Get an inside look at how we’ve improved the process to lower water levels at Lake Johnson before a storm. We used to go to the lake to manually lower water levels to reduce flooding impacts. Now we can do the same work from the office in minutes! 

Contact

 

Kelly Daniel
Flood Early Warning System Engineer
919-996-4020

Department:
Engineering Services
Service Categories:
Stormwater
Related Services:
Track Storms with Us

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