The past few days have required constant monitoring of our rivers. A lot of terminology has been thrown around like river stage, action stage, and flood stage, but what does it all mean?
“A river stage is basically the level above the river bed that the water is at so it’s so many feet above the bottom of the river,” says National Weather Service Hydrology Program Manager, Maureen Hastings.
Flood stage occurs when the water reaches a certain height that becomes a hazard, and starts affecting people and places. Before a river reaches flood stage, it reaches action stage.
“It’s kind of a way for us and other users to know that okay, the river is getting close to flood stage,” says Hastings.
The NWS, Aroostook EMA, and other agencies look at river gauges to determine the river stages. The USGS has set up these river gauges on all the rivers and 10 are monitored in Aroostook County. The data from the gauges are organized into what’s called a hydrograph.
“The gauges give us a visual picture of what’s going on in that spot the particular time that we select it. It gives us a few days data,” says the Director of the Aroostook Emergency Management Agency, Darren Woods.
When there’s big fluctuation on the hydrograph either up or down, they know they have ice movement. So when there’s a spike in the graph, that means the water levels are rising because something is blocking part of the river. The graph also shows the levels where minor, moderate, and major flooding would occur for that specific river. Hastings says these are based on impact.
“Usually minor flooding tends to be a road or two closed, maybe a few fields flooded, but as you get into the moderate and major flooding, that’s when we see more significant impacts,” says Hastings.
Woods says after they have checked the gauges, they can decide what needs to be done next.
“At that point we can either go out and do site visits by road, or we partner with the Maine Forest Service who allows us to get aerial views of what’s going on on our rivers,” says Woods.
So as you can see, there’s a lot to flood monitoring.