The city of Chehalis is located in Washington state and rests upon the Chehalis River. Due to the city's location in the Chehalis Valley along with the nearby confluences of the Newaukum River south of Chehalis and the Skookumchuck River in neighboring Centralia, the community has suffered from numerous floods. Some floods have occurred resulting from overflows of creeks and minor tributaries in the Chehalis river basin, and severe cresting of the Cowlitz River has occasionally led to flooding in the Chehalis area.
The flood stage levels of the Chehalis, Newaukum, and Skookumchuck have fluctuated upwards historically, based on the height of dikes, levees, and floodplain surveys. Water inundation from heavy rains and excessive snowmelt has led to a considerable number of historic flooding events in the twin cities of Centralia and Chehalis.
Accounts of floods are traced as far back as early Native American settlement and since the beginnings of the city of Chehalis. Most floods occur between November and February, with only one minor event, in April 1991, occurring after March. The 20th century recorded over two dozen notable flooding events in and around the Chehalis community.
Flood causes
Due to the flat topography of the Chehalis River watershed in the city, and a clay stratum under a thin layer of river soil, excess water is difficult to shed off the land or absorb into the ground. Successive floods can add of additional sediment, further limiting how much water can enter the ground in future floods. The rate of fall of the Chehalis River in the Twin Cities drops from a maximum per mile in the Willapa Hills down to approximately per mile.
, the flood stage for the Chehalis is set at , the Newaukum River at , and the Skookumchuck's mark at . A water flow between per second is a marker for a major flood event on the Chehalis compared to an average annual maximum of per second. Combined with the conjunction of the Skookumchuck and Newaukum rivers, the Chehalis Valley gathers floodwaters similar to a lake. Approximately 70% of the city limits of Chehalis is situated in the floodplain.
Human activities, such as upstream logging in the Chehalis River basin, have caused floods to become more severe. Clearcut logging has resulted in numerous landslides containing logs, mud, and silt that lead to congested areas, log jams, and large amounts of debris in area waterways. An increase in floodplain development and the use of fill has also been cited as a major cause to the augmented intensity of floods in the late-20th and early-21st centuries. Local government and city officials have stated that due to the large footprint of the Chehalis floodplain, fill and development have little to no effect on the severity of floods.
The risk of flooding at a level that used to constitute a 100-year flood, meaning there was a 1% chance of it occurring in any year, had increased by 33% between the 1980s and 2010s. In addition to logging and development, climate change plays a role in increasing flood risk by delivering more precipitation to upstream areas. Estimations from a 2022 climate study group that included the Office of the Chehalis Basin and the University of Washington show the Chehalis River and the surrounding watershed can be expected to experience 14 major floods every century due to a warming climate, the expectations were more than doubled, reaching a rate of 45 floods per 100 years by the mid-to-late 21st century.
Native American flood history Historical accounts and spiritual lessons passed down through the history of Native American people living in and around the Chehalis River tell of major floods in the basin. Chronicles of the Cowlitz Indian Tribe speak of floods that reached the pinnacle of Mount St. Helens leading to the beginnings of the tribe. The Chehalis people have traditional stories of floods that led to the transformation of humans and animals and how they interacted between one another and their habitat.
Flood events in the 19th century One of the first non-Native visitors to the area, botanist David Douglas, recorded several floods and highwater troubles during an expedition in 1825. Early settlers in the 1850s reported consistent flooding between the Skookumchuck and the Saundersville settlement, eventually known as the city of Chehalis. The area was considered at times to be a -wide lake, and the site of the future fairgrounds was known as "Wet Prairie".
Local residents also reported high floodwaters occurring often during the 1860s, including in the winter of 1865. A floodwater occurrence that affected the city and the Chehalis Valley, known locally as the great flood of 1867, involved the overflow of the Cowlitz River. The first bridge constructed over the Chehalis River was washed away by a log jam during a flood in 1882; the passage was rebuilt the next year. A flood in December 1887 was stated to have been due in part to heavy rains after a dry summer. Two Chehalis residents died and some local areas were underwater by as much as . River traffic, sawmill operations, and railroads were delayed.
Floods occurred in four consecutive years in the 1890s. Both the Chehalis and Newaukum rivers overflowed in mid-January 1895 as heavy rains combined with melting snow. The flood, higher than a flood the prior year, covered various rail lines. Several lower elevation areas of the city were underwater, forcing some evacuations. The event was considered the worst since 1867 though no major damage was reported. A smaller flood damaged a railroad track in November 1896. Two back-to-back minor floods occurred in December 1897, severely damaging nearby bridges, including a railroad bridge in Claquato. Between the Twin Cities, the pair of events washed out a plank road and covered the Northern Pacific rail line in of water. The second flood was caused by a combination of of rain over a four-day period and melting snow.
Flood events from 1900 to 1949
1900s
The city was cut off and lost electricity during a flood in January 1903, caused by heavy rain and snowmelt; the flood mark was below the 1897 events. A large episode of rising waters, given the name the Schoumacher Flood after a man who was stranded for three days, occurred in 1906 as the Cowlitz River affected the area, again cutting off the city. Mail and railroad service were suspended for days and the flood of the Cowlitz considered worse than the 1867 flood.
Factory areas and parts of the Pennsylvania Avenue-West Side Historic District suffered flooding in January 1909 after continuous rain and snowmelt caused the Chehalis to rise above its low water mark; residents could only move about by boat. A record-setting event followed that November and was due to the excess rise of the Chehalis and Newaukum rivers which led to landslides, the inundation of the Southwest Washington Fairgrounds, and caused significant economic losses to lumber milling in the city.
1910s A year later in November 1910 a flood similar to the 1909 event was significant enough to come close to breaking the new records. Again due to heavy rains and the overflow of both rivers, the waters also inundated the fairgrounds where the local rail tracks were covered and a small mudslide occurred. The event shut down gas service to the city for a small time. The fairgrounds were underwater during an overflow of nearby Coal and Salzer creeks in mid-January 1912. A minor flood in early January 1914, due to continuous rainfall, caused the outage of the Twin City Railroad between Centralia and Chehalis.
In December 1915, the city was hit by a flood from a storm reported by the Chehalis Bee-Nugget newspaper as the "Worst in City’s History". The Chehalis and Skookumchuck rivers overflowed and additional rain a few days later caused the banks of the Cowlitz River to be overwhelmed. Damages were reported as limited with no loss of life, but a backup of sewer lines affected parts of the city. The Twin City Railroad could not operate. Similar to other past floods, mills and factories were closed, rail lines were inoperable, and the fairgrounds were covered in water. A new road between the Twin Cities was covered in of water, mudslides were reported in the area, and electricity had to supplanted by the local steam plant as larger power operators in the region were forced to shut down.
Four years later, in January 1919, a deluge was declared by the Centralia Daily Chronicle as, "Present Flood Probably Worst in City’s History". The three major rivers in the area overflowed with landslides disconnecting travel, communities, and electricity in the area. The elementary and high school were briefly closed. The flood was mentioned in regional newspaper accounts to have broken the record for highest depth but gauges reported that the waters fell short of the mark.
1920 to 1949 Except for a small inundation of lowland flooding occurring between late December 1920 and early January 1921, in which the Chehalis River came within two feet of the crest record, the city was spared any flooding events of note for twelve years. In December 1933, Chehalis was submerged in a month-long rain event, totaling over of precipitation. The heavy rains affected most of Western Washington including roads between Portland and Tacoma and the submergence of the Pacific and Ocean Beach highways.
Passage between the Twin Cities was closed, and railroad traffic and postal services were disrupted in Chehalis. The city water supply was reduced due to damaged intakes and soil entering the reservoir. Alexander Park and the fairgrounds flooded, the latter of which had water levels up to the eaves in some buildings. Flood records were broken and damages were estimated to be as high as $50,000 in the county (2024 value of $1.3 million).
Successive events of heavy rainfall in early 1936, and excess rain mixed with snowstorms in February 1937, led to additional moderate flooding. A 1939 flood from a rain on snow event submerged the Chehalis–Centralia Airport.
A Cowlitz River overflow in 1946 affected the city. The weather pattern that caused the 1948 Columbia River flood was a widespread disaster throughout the region and both the Chehalis and Newaukum crested, leading to closures of roads and the airport. A 1949 rainfall event affected the city as the Cowlitz overflowed.
Flood events from 1950 to 1999
1950s Heavy rains in February and March 1951 caused moderate, local flooding. A flash flood in December 1953 clogged intakes of the local water system but the city's reservoir was ample enough that no shortage to residents occurred. Heavy rain showers continued into January 1954 causing lowland flooding with some inundation of the Ocean Beach and Pacific highways, the latter of which being a predecessor of Interstate 5. Gauges at the Chehalis River reached over .
Two minor December 1955 inundations occurred due to a quick rise in the water of the Chehalis River. The second event was due to a combination of melting snow and near-record rain. The Chehalis River crested at . A wind event, described as a "twister", hit the area the day after the river began to recede. Two minor floods, with the Chehalis and Skookumchuck rivers barely reaching or surpassing flood stage, occurred in November and December 1959. The November flood, with the Chehalis River reaching a foot over flood stage, did cause flooding in some neighborhoods.
1960s
The highest flood levels in over a decade occurred in January 1964 with the Chehalis River overflowing above flood stage. Due to excessive rainfall over a two-day period, flooding was considered moderate with water covering local neighborhood streets, Alexander Park. A few businesses were unable to operate.