Editor’s note: The Garden Island is beginning a series of stories today, which will continue this week, on the one-year anniversary of the flooding that devastated much of the island. We will look at the the impacts of the flood, the recovery, how things stand today and what’s ahead.
WAINIHA — A year ago today, dozens of homes collapsed into rising waters on Kauai. Taro fields were wiped out. Businesses were inundated with water. Black Pot Beach Park virtually disappeared under a raging Hanalei River.
It was thanks to a thunderstorm that parked over Wainiha and Hanalei, dropping 49.69 inches on the night of April 14, 2018 and breaking national records that had been in place since 1979.
The North Shore wasn’t the only place on Kauai that got drenched during that April 14-15 storm, and it wasn’t the only one to pass through in 2018.
It wasn’t even the first.
Rainfall numbers took a leap in February 2018 after January’s large-scale shift in weather patterns, kicking off an upward trend in rainfall and making for the wettest February across the island chain in a decade, according to the National Weather Service.
Hanalei, for example, recorded 18.45 inches by Feb 18, 2018 — 253 percent of the monthly average of 7.30 inches. Wainiha received 15.88 inches by Feb. 18, 167 percent of the monthly average of 11.67 inches.
It started in February
The first heavy rain that produced damage on Kauai was on Feb. 4, where some areas recorded more than 7 inches of rainfall in one 24-hour period and minor flooding. Again, on Feb. 22, heavy rainfall caused problems on Kauai.
The Feb. 22 rains overflowed the Hanalei River and closed Kuhio Highway by the Hanalei Bridge. By the time Feb. 23 rolled around, the first of many landslides started closing Kuhio Highway between Wainiha and Lumahai.
Trade winds gave Hawaii a little break at the beginning of March, but low-pressure systems brought heavy rains back to Kauai before the initial landslides were even fully cleared and slopes repaired.
NWS points out the “first and arguably most significant” of these rain events was on March 14 and 15. The storm made an impact statewide, but particularly on Kauai.
“Heavy rainfall on Kauai produced flash flooding in Hanalei River during two episodes, both of which forced the closure of Kuhio Highway for several hours near the Hanalei Bridge,” Kevin Kodama, senior service hydrologist, said in his monthly report on the rainfall. “Landslides near Lumahai also impacted Kuhio Highway on multiple occasions.”
By April, the last month of the wet season, Kauai was already seeing above average rainfall. Then, the storm of the century showed up.
“Usually, heavy rain event frequency drops off and rainfall totals decrease (in April),” Kodama said in his summary of April 2018 rainfall. “Not this year. The most significant events of the entire wet season, both in terms of hydrologic magnitude and impacts to the public, occurred in mid-April 2018.”
An upper level low-pressure system and low-level trade winds worked together and produced torrential rainfall and severe flooding over Kauai and Oahu from late Friday, April 13 through Sunday, April 15, 2018, NWS says.
On Kauai, the rainfall event that would break records started shortly before midnight on Saturday, April 14. Soon, Kuhio Highway at Haena and at the Hanalei Bridge were closed. The storm let up by 8 a.m. Saturday morning, resulting in the highway opening again at Hanalei Bridge.
That lasted until about noon, when the first of three rainstorms kicked to life over North Kauai.
“Unlike most heavy rain events which affect the island, this round of rainfall was centered along the lower elevations and coastal sections instead of over the upper slopes. Around this time several landslides between Waikoko and Wainiha closed Kuhio Highway. As rainfall continued through the afternoon, severe flooding washed out the Wainiha Powerhouse Road and destroyed two unoccupied homes,” Kodama says in his summary.
But, that was just the first round.
The second started around midnight on April 15 and rainfall rates of more than 5 inches per hour were recorded at the peak of that second event, NWS data shows. Flash flooding put parts of Kuhio Highway 5 to 8 feet underwater as the Hanalei River overflowed. Wainiha River and Kilauea Stream also flooded.
Then, the storm moved.
By the time it settled about 8 a.m. on April 15, both Kapaa Stream and Anahola Stream had overflowed and their waters were destroying properties and threatening homes.
Rain bands redeveloped over Kauai two hours later and Kuhio Highway went back underwater at Hanalei Bridge, resulting in highway closure. Hanalei flooded.
Then, the storm moved again.
This time, further south to drop more than 4 inches per hour of water over the eastern and southestearn parts of Kauai. That triggered flooding in Koloa and Kalaheo and damaged homes off of Wailaau Road.
At sunset on April 15, that last storm dissipated, leaving destruction and devastation in its wake. On that night, from April 14 to April 15, Wainiha set a new national record of 49.69 inches.
The previous record was set in 1979 with 43 inches in a 24-hour period in Alvin, Texas.
Not over yet
Kauai welcomed the dry season with much calmer weather in May 2018, but rainfall totals landed at near-to-above average, according to Kauai gauges.
June and July settled into regular patterns and people on Kauai dove into recovery.
Federal funds helped some of those displaced, dozens of workers flooded to Kuhio Highway to begin repairs, volunteers and organizations worked together to clean classrooms and yards from debris, fix foundations and homes that were wiped out.
But the weather wasn’t done with the state. August brought the hurricane season in full force — namely Hurricane Lane with its own record-breaking rains and damaging floods that hit Hawaii Island, Maui, Oahu and Kauai.
That storm produced swollen streams and one death — a Kauai man who jumped into Waikomo Stream to save a dog.
Minor flooding continued on Kauai through September after a weakened Hurricane Olivia passed through — bringing Kokee its highest September rainfall on record, 6.83 inches in 24 hours, 293 percent of average.
It remained significantly wet through the rest of the year, but dried out significantly when January 2019 came around. Cleanup from the storms continues to this day on Kauai, with rebuilding efforts underway in Wainiha and on Kuhio Highway.
••• Jessica Else, environment reporter, can be reached at 245-0452 or at firstname.lastname@example.org