Flood watch in effect as Tacoma Power increases flow on Nisqually River
EDITOR’S NOTE: This story was updated Tuesday with additional details about flood watches.
Tacoma Power increased the water flowing out of the LaGrande Dam Monday, prompting Thurston County Emergency Management to issue an alert for residents along the Nisqually River.
The county sent out the advisory through its Thurston Community Alert System. It said the power utility increased the flow from 4,000 cubic foot per second at 11 a.m. up to 7,500 cubic foot per second by 4 p.m. The change is meant to manage water levels, the alert read.
Similar flow releases by Tacoma Power in January and February 2020 led to extensive flooding and evacuations in the Nisqually River valley. The alert issued today echoes similar alerts that preceded the destructive flood waters last year when a planned increase to 6,200 cfs escalated to a peak of 15,000 cfs.
The flooding last year followed record breaking rain-fall in January.
A flood watch is currently in effect for Thurston County through Wednesday evening, according to the National Weather Service in Seattle.
Heavy rain is expected in amounts of 1 to 3 inches in the lowlands, according to the weather service. The highest risk for flooding is focused on the Olympic Peninsula and in lowlands south of Seattle, the latest alert read.
For now, the increased flows from the dam are expected to cause erosion only on farms and pastureland, according to the alert, but it is possible that Tacoma Power may increase the flow as weather conditions change, the alert read.
As a precaution, the alert directs residents to take steps to protect their property in the valley. However, the Nisqually River water levels are currently forecast to remain below even the minor flood stage through Sunday, according to the National Weather Service’s Advanced Hydrologic Prediction Service.
The 217 feet high and 710 feet long LaGrande Dam is one of two Tacoma Power electric dams on the Nisqually River, according Tacoma Public Utilities. Its reservoir covers about 45 acres and the average flow from the dam is about 1,400 cfs.
County emergency services director Kurt Hardin said Tacoma Power planned to increased the water flow up to 8,000 cfs, the threshold for minor flooding, but they decided to lower the flow to 7,500 cfs after the county expressed concerns.
Other rivers are forecast to experience minor flooding. The National Weather Service issued a flood warning for the Chehalis River above Grand Mound on Tuesday, according to an alert from Thurston County Emergency Management. The warning is in effect until Thursday evening, the alert read.
The Chehalis River is expected to reach a minor flood stage around 4 a.m. Wednesday, Hardin said Tuesday. From there, the flood stage will likely peak by around 10 p.m. Wednesday and drop below the minor flood stage by around 4 p.m. Thursday, he added.
At a peak height of about 141 feet, the Chehalis River will likely flood several roads in Independence Valley such as James Road, Independence Road and Moon Road. Flood waters also are expected to cover nearby farm lands, the release read.
Additionally, the Skookumchuck River is forecast to reach minor flood stage by around 4 a.m. Wednesday, Hardin said. He added, the flood stage is expected to crest at about 10 a.m. Wednesday and drop below the minor flood stage around 10 p.m. Wednesday.
Residents in potential flood zones can get sandbags at local fire stations, although they may need to fill the sandbags themselves. A complete list of sand bag locations can be found on the Thurston County Emergency Management website.
This story was originally published January 11, 2021 at 3:52 PM.
