How does the National Weather Service determine when rising rivers will crest, and how do they figure out how high the rivers will get?

Andy Patrick, meteorologist-in-charge at the National Weather Service office in Lake Charles, said hydrologists with the weather service’s river forecast centers use gauge observations and modeling to help determine how high rivers will rise at particular locations.

The models help hydrologists determine the rise and fall of river levels, along with their crests, and the timing of each occurrence, he said. 

“The National Weather Service weather forecast offices, like here in Lake Charles, take this information and help to provide impacts for their area. This includes impacts for highways, communities or other known locations that would potentially flood,” Patrick wrote in an email.

“For example, we have a forecast point along the Sabine River in Deweyville. But what does that mean in Louisiana? We try to determine if water will be on Highway 12 and if flooding will occur at Niblett’s Bluff Park. How will it impact the communities of Starks and Toomey?”

Record crests for various points along the Sabine River, according to weather service data:

Deweyville, Texas

33.28 feet — March 15, 2016.

32.2 feet — May 1, 1884.

29.98 feet — May 22, 1953.

29.5 feet — April 29, 1913.

29.15 feet — July 6, 1989.

Flood stage is 24 feet.

Orange, Texas

9.86 feet — Sept. 13, 2008.

7.62 feet — March 17, 2016.

6.27 feet — April 25, 1913.

5.92 feet — July 8, 1989.

5.77 feet — Aug. 23, 1915.

Flood stage is 4 feet.

Record crests for various points along the Calcasieu River:

Old Town Bay

16.1 feet — May 21, 1953.

13.9 feet — July 2, 1989.

12.5 feet — Aug. 10, 1940.

11.5 feet — Nov. 8, 2002.

11.2 feet — Sept. 13, 2008.

Flood stage is 4 feet.

Sam Houston Jones Park

14.4 feet — Dec. 29, 1982.

12.75 feet — May 22, 1953.

11.82 feet — May 18, 1980.

11.07 feet — July 2, 1989.

10.9 feet — Oct. 28, 2006.

Flood stage is 5 feet.

Saltwater Barrier

13 feet — Oct. 1, 1913.

11 feet — Sept. 13, 2008.

9.43 feet — Sept. 24, 2005.

9.4 feet — July 3, 1989.

8.95 feet — Dec. 31, 1982.

Flood stage is 4 feet.

To view the weather service’s gauge data, go to www.weather.gov/lch and click on the “Rivers and Lakes” link. From there you can access a hydrograph showing the readings from a gauge site by clicking on the map.

The Informer answers questions from readers each Sunday, Monday and Wednesday. It is researched and written by Andrew Perzo, an American Press staff writer. To ask a question, call 494-4098 and leave voice mail, or email informer@americanpress.com.