:2018 Hawaii floods

{{Short description|Record-breaking rainfall on the Hawaiian Islands of Kauaʻi and Oahu}}

{{Infobox flood

|name=2018 Hawaii floods

|image name=Radar loop of mesoscale convective system striking Oahu on April 13

|image location=Oahu radar April 13, 2018 convective system.gif

|duration=April 13–15, 2018

|total damages=$125 million (2018 USD){{#tag:ref|All damage totals are in 2018 United States dollars.|group="nb"}}

|total fatalities=None reported

|areas affected=Kauai, Oahu (Hawaii)

}}

In April 2018, a series of thunderstorms produced record-breaking rainfall on the Hawaiian Islands of Kauaʻi and Oahu. An upper-level low moved across the area on April 13, generating a mesoscale convective system that moved over eastern Oahu, producing localized heavy rainfall that reached {{convert|5.55|in|mm|abbr=on}}. The heaviest rainfall occurred on northern Kauaʻi. There, a rain gauge owned by the Waipā Foundation, just west of Hanalei, recorded {{convert|49.69|in|mm|abbr=on}} of rainfall in the 24 hours between 12:45 p.m. on April 14 and 15.{{#tag:ref|All times in this article are in local Hawaiian Standard Time.|group="nb"}} This was the greatest 24-hour rainfall total on record in the United States, surpassing the previous record of {{convert|43|in|mm|abbr=on}} in Alvin, Texas on July 25–26, 1979, set during Tropical Storm Claudette. Through the event, the same gauge recorded a total of {{convert|54.37|in|mm|abbr=on}} of rain.

The heavy rainfall produced flash flooding and landslides that covered roads and washed away several vacant houses. The floods damaged or destroyed 532 houses. Public damage totaled $19.7 million and overall damage was estimated at over $125 million. Damage on Kauai was the worst from a natural disaster since Hurricane Iniki in 1992. Landslides and flooding covered parts of Kuhio Highway.

Meteorological history

On April 11, 2018, an upper-level low was located west of the Hawaiian island of Kauaʻi. The low moved toward Hawaii and drew deep tropical moisture from the south. The low eventually opened into a trough, which crossed over the Hawaiian islands on April 13. That day, a mesoscale convective system (MCS) developed northwest of Molokai and intensified while moving westward through the trade winds. The MCS moved over eastern Oahu, dissipating after moving ashore. Another upper-level low developed on April 14, fueling additional rainfall through April 16, which caused record rainfall on Kauaʻi. The first of a series of thunderstorms moved over northern Kauaʻi around midnight on April 14. After a five-hour break in rainfall, another set of thunderstorms hit northern Kauaʻi around midnight on April 15 and lasted about eight hours. The third set of thunderstorms began around 10 AM on April 15 and continued until around 7 PM.{{cite report|title=Kauai and Oahu Flash Flooding - April 13 - 15, 2018|publisher=Honolulu, Hawaii National Weather Service|year=2018|url=http://www.prh.noaa.gov/hnl/pages/events/KauaiOahuApril2018Floods/|access-date=January 12, 2019|archive-date=January 13, 2019|archive-url=https://web.archive.org/web/20190113062903/http://www.prh.noaa.gov/hnl/pages/events/KauaiOahuApril2018Floods/|url-status=dead}}

Impact

The Honolulu National Weather Service issued various flash flood watches and warnings.{{cite news|title=Floodwaters destroy homes, cause mudslides on Kauai|access-date=February 1, 2019|date=April 14, 2018|newspaper=The Honolulu Star Advertiser|url=https://www.staradvertiser.com/2018/04/14/breaking-news/kauai-under-a-flash-flood-warning/|archive-date=February 2, 2019|archive-url=https://web.archive.org/web/20190202095723/https://www.staradvertiser.com/2018/04/14/breaking-news/kauai-under-a-flash-flood-warning/|url-status=live}} The trough began dropping heavy rainfall over Hawaii on April 13. Floods damaged or destroyed 532 houses. The flooding knocked down trees and power lines, eroded many bridges and roads, and washed away crops, beehives, and livestock. Overall damage was estimated at over $125 million. Damage to public buildings was estimated at $19.7 million. Despite the damage, there were no deaths or injuries.{{cite report|title=April 13 Hawaii Heavy Rain Event|publisher=National Climatic Data Center|access-date=February 1, 2019|url=https://www.ncdc.noaa.gov/stormevents/eventdetails.jsp?id=741670|series=Storm Events|archive-date=February 2, 2019|archive-url=https://web.archive.org/web/20190202042445/https://www.ncdc.noaa.gov/stormevents/eventdetails.jsp?id=741670|url-status=live}}{{cite news|date=September 21, 2018|author=Jade Snow|title=Farmers Rebuild After the Devastating Floods on Kauai and Oahu|newspaper=Hawaii Magazine|url=https://www.hawaiimagazine.com/content/farmers-rebuild-after-devastating-floods-kauai-and-oahu|access-date=February 1, 2019}}{{cite report |title=Weather, Climate & Catastrophe Insight: 2018 Annual Report |url=http://thoughtleadership.aonbenfield.com/Documents/20190122-ab-if-annual-weather-climate-report-2018.pdf |website=AON Benfield |page=60 |access-date=March 8, 2019 |archive-date=February 14, 2019 |archive-url=https://web.archive.org/web/20190214230802/http://thoughtleadership.aonbenfield.com/Documents/20190122-ab-if-annual-weather-climate-report-2018.pdf |url-status=dead }}

=Oahu=

Across eastern Oahu, the mesoscale convective system produced rainfall rates of about {{convert|4|in|mm|abbr=on}} per hour. Over a 15-minute period, a rain gauge in Niu Valley recorded {{convert|1.42|in|mm|abbr=on}} of precipitation, which has a 4–10% annual return period. The same station recorded {{convert|5.52|in|mm|abbr=on}} of rainfall over a two-hour period, which has a 0.5–1% annual return period. The rainfall on Oahu was largely limited to the eastern one-third of the island. A station at Daniel K. Inouye International Airport recorded {{convert|0.01|in|mm|abbr=on}} of rainfall, just {{convert|14|mi|km|abbr=on}} west of Niu Valley, which recorded {{convert|5.55|in|mm|abbr=on}} during the same 24-hour period.

At Waimanalo Stream north of Niu Valley, the rains caused the waters to rise {{convert|3|ft|m|abbr=on}} in 30 minutes, and {{convert|5|ft|m|abbr=on}} in an hour. During the rain event, Wailupe Gulch reported an {{convert|8|ft|m|abbr=on}} rise in floodwaters. Flooding entered cars and hundreds of houses on Oahu.{{cite news|title=East Oahu residents are still dealing with the impact of historic rain five months after the flood|access-date=February 1, 2019|author=Jenn Boneza |date=September 14, 2018|publisher=KHON2|url=https://www.khon2.com/news/local-news/east-oahu-residents-are-still-dealing-with-the-impact-of-historic-rain-five-months-after-the-flood/1446761857}} The floods also caused significant runoff, leaving a layer of debris on roads. A portion of Kalanianaole Highway was covered with nearly {{convert|1|ft|mm|abbr=on}} of water, closing a stretch of the highway from Aina Haina to Makapuʻu.{{cite report|title=April 13 Hawaii Flash Flood Event|publisher=National Climatic Data Center|access-date=February 1, 2019|url=https://www.ncdc.noaa.gov/stormevents/eventdetails.jsp?id=742752|series=Storm Events|archive-date=February 2, 2019|archive-url=https://web.archive.org/web/20190202042013/https://www.ncdc.noaa.gov/stormevents/eventdetails.jsp?id=742752|url-status=live}} A mudslide covered a portion of the same highway near Kailua.{{cite report|title=April 13 Hawaii Debris Flow Event|publisher=National Climatic Data Center|access-date=February 1, 2019|url=https://www.ncdc.noaa.gov/stormevents/eventdetails.jsp?id=742754|series=Storm Events|archive-date=February 2, 2019|archive-url=https://web.archive.org/web/20190202042140/https://www.ncdc.noaa.gov/stormevents/eventdetails.jsp?id=742754|url-status=live}} Downed trees closed one block of Maunaloa Avenue in Kaimuki.{{cite report|title=April 13 Hawaii Thunderstorm Wind Event|publisher=National Climatic Data Center|access-date=February 1, 2019|url=https://www.ncdc.noaa.gov/stormevents/eventdetails.jsp?id=742753|series=Storm Events|archive-date=February 2, 2019|archive-url=https://web.archive.org/web/20190202042235/https://www.ncdc.noaa.gov/stormevents/eventdetails.jsp?id=742753|url-status=live}}

=Kauaʻi=

On Kauaʻi, the rainfall event occurred at low elevations near the northern coast. This was unusual, as previous rain events on the island usually occurred over higher elevations. The heaviest rainfall was early on April 15. A rain gauge owned by the Waipā Foundation, just west of Hanalei on Kauaʻi's northern coast, recorded {{convert|49.69|in|mm|abbr=on}} of rainfall in the 24 hours ending at 12:45 p.m. local time. The total greatly surpassed the Hawaiʻi 24-hour rainfall record of {{convert|38|in|mm|abbr=on}} set on January 25, 1956, at Kīlauea. The total also broke the national 24-hour rainfall record of {{convert|43|in|mm|abbr=on}} set during Tropical Storm Claudette on July 25–26, 1979 in Alvin, Texas, a record confirmed in December 2018.{{cite report|publisher=National Centers for Environmental Information|work=National Climate Extremes Committee|author=Deke Arndt|author2=Jim Zdrojewski|author3=Pao-Shin Chu|date=December 14, 2018|access-date=February 1, 2019|title=National Record 24-Hour Precipitation at Waipā Garden, Hawai'i|url=https://www.ncdc.noaa.gov/monitoring-content/extremes/ncec/precip-24hr-kauai-2018.pdf|archive-url=https://web.archive.org/web/20190509061102/https://www.ncdc.noaa.gov/monitoring-content/extremes/ncec/precip-24hr-kauai-2018.pdf|archive-date=May 9, 2019|url-status=dead}}{{cite web|author=David M. Roth|access-date=April 25, 2018|date=November 29, 2017|title=Tropical Storm Claudette - July 16-31, 1979|url=http://www.wpc.ncep.noaa.gov/tropical/rain/claudette1979.html|publisher=Weather Prediction Center|archive-date=September 22, 2013|archive-url=https://web.archive.org/web/20130922065006/http://www.wpc.ncep.noaa.gov/tropical/rain/claudette1979.html|url-status=live}} The Waipā rain gauge also recorded {{convert|1.77|in|abbr=on}} over 15 minutes, {{convert|5.51|in|mm|abbr=on}} over an hour, {{convert|19.52|in|mm|abbr=on}} over six hours, {{convert|33.33|in|mm|abbr=on}} over 12 hours, and {{convert|54.37|in|mm|abbr=on}} over 48 hours. Elsewhere on northern Kauaʻi, a rain gauge in Wainiha recorded {{convert|32.35|in|mm|abbr=on}}, and a gauge in Hanalei recorded {{convert|28.41|in|mm|abbr=on}} before it failed. Minimal rainfall occurred on the southern and western coasts of Kauaʻi. The intense rainfall washed out several river gauges. Along the Hanalei River, the United States Geological Survey (USGS) estimated that floodwaters rose {{convert|15|ft|m|abbr=on}}, representing a peak flow rate of 32,700 cubic feet per second (ft³/s, 926 m³/s) before the station failed. The Wainiha River reported a record flow rate during the event.

The rain event caused the worst natural disaster in Kauai since Hurricane Iniki in 1992.{{cite news|date=April 19, 2018|title=Historic Floods, Landslides Devastate The Hawaiian Island Of Kauai|newspaper=The Huffington Post|access-date=February 1, 2019|author=Carla Herreria|url=https://www.huffingtonpost.com/entry/kauai-flooding-landslides_us_5ad14167e4b077c89ce8b616|archive-date=January 31, 2019|archive-url=https://web.archive.org/web/20190131123010/https://www.huffingtonpost.com/entry/kauai-flooding-landslides_us_5ad14167e4b077c89ce8b616|url-status=live}} The sudden rains caused landslides, mostly in isolated areas, as well as flash flooding, causing power outages in Hanalei and Wainiha. Rising waters washed out four vacant homes and entered dozens of others. The rising waters forced guests at the Hanalei Colony Resort to move to the second floor. The floodwaters reached {{convert|8|ft|m|abbr=on}} deep near Hanalei, closing parts of Kuhio Highway. Landslides occurred at 15 locations along the highway, leaving residents in Wainiha and Haena without regional road access, disrupting relief efforts.{{cite news|publisher=Weather.com|access-date=April 25, 2018|title=Kauai Flooding Eases But Damage Is Worse Than Expected, Aerial Survey Shows|date=April 19, 2018|url=https://weather.com/news/news/2018-04-15-hawaii-heavy-rain-flood-mudslides-impacts|archive-date=April 17, 2018|archive-url=https://web.archive.org/web/20180417084006/https://weather.com/news/news/2018-04-15-hawaii-heavy-rain-flood-mudslides-impacts|url-status=live}}{{cite report|title=April 13 Hawaii Flash Flood Event|publisher=National Climatic Data Center|access-date=February 1, 2019|url=https://www.ncdc.noaa.gov/stormevents/eventdetails.jsp?id=742772|series=Storm Events}}{{cite report|title=April 13 Hawaii Debris Flow Event|publisher=National Climatic Data Center|access-date=February 1, 2019|url=https://www.ncdc.noaa.gov/stormevents/eventdetails.jsp?id=742756|series=Storm Events}} Three bridges along the route were damaged, which delayed repairs, leaving the Kuhio Highway closed as of November 2018.{{cite news|title=Stretch of Kuhio Hwy. damaged by floods to remain closed until 2019|date=November 8, 2018|newspaper=Hawaii News Now|access-date=February 1, 2019|url=http://www.hawaiinewsnow.com/2018/11/08/stretch-kuhio-hwy-damaged-by-floods-remain-closed-till/|archive-date=February 2, 2019|archive-url=https://web.archive.org/web/20190202095907/http://www.hawaiinewsnow.com/2018/11/08/stretch-kuhio-hwy-damaged-by-floods-remain-closed-till/|url-status=live}} Residents used a {{convert|1|mi|km|abbr=on}} detour on a dirt road.{{cite news|title=Detour taking toll|author=Jessica Else|newspaper=The Garden Island|date=November 20, 2018|access-date=February 1, 2019|url=https://www.thegardenisland.com/2018/11/20/hawaii-news/detour-taking-toll/|archive-date=February 2, 2019|archive-url=https://web.archive.org/web/20190202095843/https://www.thegardenisland.com/2018/11/20/hawaii-news/detour-taking-toll/|url-status=live}} The flooding forced the temporary closure of three beaches – Kalapaki Beach, Koloa Landing, and Moloaa Bay – as well as two parks, Nā Pali Coast State Park and Haʻena State Park. Wainiha and Haena residents were urged to limit their water use due to contaminated water supply.{{cite news|title=Kalalau Trail closure redirects visitors elsewhere on Kauai|author=Jessica Else|newspaper=The Garden Island|date=September 13, 2018|access-date=February 1, 2019|url=https://www.thegardenisland.com/2018/09/13/hawaii-news/kalalau-trail-closure-redirects-visitors-elsewhere-on-kauai/|archive-date=February 2, 2019|archive-url=https://web.archive.org/web/20190202095847/https://www.thegardenisland.com/2018/09/13/hawaii-news/kalalau-trail-closure-redirects-visitors-elsewhere-on-kauai/|url-status=live}}

Aftermath and records

Kauai Mayor Bernard Carvalho Jr. declared a state of emergency for portions of Kauai, which effectively restricted tourist operations in the Hanalei area. He extended the emergency four more times, effective through January 4, 2019.{{cite news|title=Fire hits Kauai resort already devastated by flooding|date=July 29, 2018|author=Leila Fujimori|newspaper=Honolulu Star Advertiser|access-date=February 1, 2019|url=https://www.staradvertiser.com/2018/07/29/hawaii-news/fire-hits-resort-already-devastated-by-flooding/|archive-date=February 2, 2019|archive-url=https://web.archive.org/web/20190202095752/https://www.staradvertiser.com/2018/07/29/hawaii-news/fire-hits-resort-already-devastated-by-flooding/|url-status=live}}{{cite news|date=November 6, 2018|title=Mayor signs fifth emergency proclamation|newspaper=The Garden Island|access-date=February 1, 2019|url=https://www.thegardenisland.com/2018/11/06/hawaii-news/mayor-signs-fifth-emergency-proclamation/|archive-date=February 2, 2019|archive-url=https://web.archive.org/web/20190202095812/https://www.thegardenisland.com/2018/11/06/hawaii-news/mayor-signs-fifth-emergency-proclamation/|url-status=live}} After the floods, Hawaiian Governor David Ige also declared a State of Emergency. On April 18, the Hawaii legislature approved $125 million in disaster funding, including $100 million for Kauaʻi. On May 8, President Donald Trump declared a federal disaster area for Kauaʻi and Honolulu counties. Initially, the declaration was limited to federal reimbursement for repairs to public infrastructure, but on June 27 it was expanded to include individual assistance. Ultimately, the Federal Emergency Management Agency (FEMA) approved 250 individual assistance applications, totaling about $1.5 million, with another $2.6 million in public assistance grants. FEMA opened three disaster recovery centers, which provided resources for the application process; these centers closed by July 20.{{cite web|title=Hawaii Severe Storms, Flooding, Landslides, And Mudslides (DR-4365)|year=2018|publisher=Federal Emergency Management Agency|access-date=January 12, 2019|url=https://www.fema.gov/disaster/4365|archive-date=January 13, 2019|archive-url=https://web.archive.org/web/20190113003928/https://www.fema.gov/disaster/4365|url-status=live}} On November 30, Carvalho granted $500,000 to six nonprofits for counselors, meals, emergency supplies, and rebuilding parts of the Limahuli Garden and Preserve.{{cite news|date=December 3, 2018|title=$500K in flood relief released|author=Daniel Fujimoto|publisher=The Garden Island|url=https://www.thegardenisland.com/2018/12/03/hawaii-news/500k-in-flood-relief-released/|access-date=February 1, 2019|archive-date=February 2, 2019|archive-url=https://web.archive.org/web/20190202095834/https://www.thegardenisland.com/2018/12/03/hawaii-news/500k-in-flood-relief-released/|url-status=live}}

Local and national emergency crews rescued people from their flooded homes by helicopter, boat, and bus, including 475 by helicopter; more than 40% of those rescued by helicopter were tourists.{{cite news|title=More Victims Of The Kauai Flood — Tourist Vacation Rentals|author=Brittany Lyte|date=May 10, 2018|access-date=February 1, 2019|newspaper=Honolulu Civil Beat|url=https://www.civilbeat.org/2018/05/more-victims-of-the-kauai-flood-tourist-vacation-rentals/|archive-date=February 2, 2019|archive-url=https://web.archive.org/web/20190202100910/https://www.civilbeat.org/2018/05/more-victims-of-the-kauai-flood-tourist-vacation-rentals/|url-status=live}} The Hawaii Department of Transportation ran convoys throughout the day along the damaged portions of Kuhio Highway while it was being repaired. The cost of reconstructing the highway was estimated at $100 million; much of it was covered by the federal government. In August 2018, Hurricane Lane dropped heavy rainfall in the same area, causing further flooding damage to houses and the Kuhio Highway.{{cite news|title=Remnants from Lane lengthen timeline for Kuhio Highway emergency repairs|date=September 2, 2018|author=Lisa Kubota|newspaper=Hawaii News Now|access-date=February 1, 2019|url=http://www.hawaiinewsnow.com/story/39025406/remnants-from-lane-lengthen-timeline-for-kuhio-highway-emergency-repairs/|archive-date=February 2, 2019|archive-url=https://web.archive.org/web/20190202153613/http://www.hawaiinewsnow.com/story/39025406/remnants-from-lane-lengthen-timeline-for-kuhio-highway-emergency-repairs/|url-status=live}}{{cite news|title=After April's historic flooding some Hanalei residents said 'the damage has been done' – then Lane plowed through|date=September 1, 2018|agency=CNN|publisher=CW39|author=Lisa Kubota|access-date=February 1, 2019|url=https://cw39.com/2018/09/01/after-aprils-historic-flooding-some-hanalei-residents-said-the-damage-has-been-done-then-lane-plowed-through/|archive-date=February 2, 2019|archive-url=https://web.archive.org/web/20190202095801/https://cw39.com/2018/09/01/after-aprils-historic-flooding-some-hanalei-residents-said-the-damage-has-been-done-then-lane-plowed-through/|url-status=live}} The Hanalei post office, damaged by the floods, reopened on July 30.{{cite news|date=July 29, 2018|title=Flood-damaged Hanalei Post Office reopens on Monday|access-date=February 1, 2019|newspaper=KITV4|url=http://www.kitv.com/story/38761990/flood-damaged-hanalei-post-office-reopens-on-monday|archive-date=February 2, 2019|archive-url=https://web.archive.org/web/20190202095627/http://www.kitv.com/story/38761990/flood-damaged-hanalei-post-office-reopens-on-monday|url-status=dead}} A Red Cross shelter in Kilauea housed 13 people after the event.{{cite news|date=April 17, 2018|title=Over 200 Hawaiʻi residents airlifted from Kauaʻi flooding following 30 inches of rain|newspaper=USAToday|access-date=April 25, 2018|url=https://www.usatoday.com/story/news/nation/2018/04/17/over-200-hawaii-residents-airlifted-kauai-flooding-following-30-inches-rain/526006002/|archive-date=April 22, 2018|archive-url=https://web.archive.org/web/20180422080350/https://www.usatoday.com/story/news/nation/2018/04/17/over-200-hawaii-residents-airlifted-kauai-flooding-following-30-inches-rain/526006002/|url-status=live}} Some of the displaced stayed with family or friends.{{cite news|date=July 10, 2018|author=Scott Giarman|title=Flood Recovery Continues on Kaua'i|newspaper=Scott Giarman|access-date=February 1, 2019|url=http://www.hpr2.org/post/flood-recovery-continues-kaua-i|archive-url=https://web.archive.org/web/20180710225455/http://hpr2.org/post/flood-recovery-continues-kaua-i|url-status=dead|archive-date=July 10, 2018}} The Hanalei Colony Resort evacuated its guests on April 16 and remained closed through October. It temporarily housed National Guardsmen and families displaced by the floods. At least two dozen students used the resort as a temporary school.{{cite news|date=August 13, 2018|title=Hanalei Colony Resort to remain closed as Kauai recovers from floods|newspaper=Hawaii News Now|access-date=February 1, 2019|url=http://www.hawaiinewsnow.com/story/38452886/hanalei-colony-resort-to-remain-closed-as-kauai-recovers-from-floods/}}{{cite news|title=Kauai students from flood areas will start school year at temporary campus|date=August 4, 2018|author=Christie Wilson|newspaper=Honolulu Star Advertiser|access-date=February 1, 2019|url=https://www.staradvertiser.com/2018/08/04/hawaii-news/kauai-students-from-flood-areas-will-start-school-year-at-temporary-campus/|archive-date=February 2, 2019|archive-url=https://web.archive.org/web/20190202095255/https://www.staradvertiser.com/2018/08/04/hawaii-news/kauai-students-from-flood-areas-will-start-school-year-at-temporary-campus/|url-status=live}} The resort's staff won the Excellence in Community Service Award at the 29th Annual Na Po‘e Pa‘ahana Awards, a ceremony for excellence in the hospitality industry.{{cite news|title=Maui Hotel Workers Honored With Industry Awards|date=January 11, 2019|access-date=February 1, 2019|newspaper=Maui Now|url=https://mauinow.com/2019/01/11/maui-hotel-workers-honored-with-industry-awards/}}

On August 2, 2018, National Weather Service Senior Hydrologist Kevin Kodama inspected and calibrated record-breaking rain gauge at Waipā Garden, confirming that the instrument was functioning normally. On December 4, 2018, the National Climate Extremes Committee verified that the {{convert|49.69|in|mm|abbr=on}} accumulation was the highest 24-hour rainfall total in the U.S.