Hurricanes, Earthquakes, Tsunamis, and Floods in Hawaii

Hurricanes in Hawaii

Hawaiian hurricanes typically form in the Pacific Ocean. Hurricane season in Hawaii is roughly from between June 1 and November 30 each year. Hawaii typically experiences about four or five tropical cyclones each year; although during the 2015 hurricane season, Hawaii had around fifteen tropical cyclones.

When was the last hurricane in Hawaii?

In July 2020, Hurricane Douglas passed north of Hawaii, bringing heavy rain and strong winds to all the islands. While the hurricane once seemed to be targeting directly at the North Shore of Oahu, it passed slightly north, causing minimal damage to the islands. This was the closest hurricane to Oahu recorded in history.

Since historical records of hurricanes or tropical cyclones in Hawaii were recorded in 1949, at least 29 people have died. The deadliest tropical cyclone to hit Hawaii was Hurricane Iniki in 1992, which killed 6 people and caused $3.1 billion in damage, much of which was on the island of Kauai.

How can I prepare for a hurricane in Hawaii?

Make sure you have a way to get information through the local news on TV, the Internet, or radio. You can also sign up for local emergency notification systems. The City & County of Honolulu as well as Hawaii, Kauai, and Maui and the entire state have emergency notification sites, which can send automatic messages if you sign up.

For hurricanes, tropical storms, and other natural disasters, it is important to prepare, especially because of Hawaii’s isolation as an island. The State of Hawaii, Office of Public Health Preparedness, recommends the following:

• Create a personal/family emergency plan to make sure everyone knows where to go in case of an emergency. Here are ideas from the Hawaii Department of Health for making a family emergency plan.
• Have an emergency kit with enough supplies to last at least 14 days. Note that emergency shelters in Hawaii do not provide food, water, medication, or bedding. Include these items in your emergency kit: Water, non-perishable food, medication, hygiene items, radio, flashlight, cash, first-aid supplies, disinfectant supplies, clothes, bedding, infant, senior or pet supplies (if applicable)
• Secure your property before a storm by clearing drains and gutters, storing outdoor items inside, boarding windows or using hurricane shutters.
• Keep your cell phone charged before the storm.
• Know your evacuation zone and possible routes to get there.
• Help your neighbors with their hurricane plans and preparations, especially older people or anyone who may need additional help.

Tsunamis in Hawaii

A tsunami is a series of giant waves from that ocean, often caused by earthquakes, underwater landslides, volcanic eruptions, or asteroids. Tsunamis can travel around 20 to 30 miles per hour and can reach heights of 100 feet. Tsunamis can cause major flooding and also disrupt transportation, power, communication, and water supplies.

What is the history of tsunamis in Hawaii?

Since 1812, there have been a total of 135 confirmed tsunamis in Hawaii, according to the International Tsunami Information Center from the United Nations.

The worst tsunami in Hawaii, in terms of damage and deaths, occurred in 1946. An 8.6 magnitude earthquake off the coast of Alaska created a 16-foot-tall tsunami that created $150 million in damage (2016 dollars). There were 158 deaths: 121 on Hawaii Island (96 in Hilo), 17 on Kauai, 14 on Maui and 6 on Oahu.

How can I prepare for a tsunami in Hawaii?

If you are living or visiting Hawaii, it is not uncommon for a tsunami warning to happen almost every year. Therefore, it is important to prepare ahead of time the best that you can.

• Learn more about the risk of a tsunami in your location and the tsunami evacuation zones and routes. Tsunami shelters will typically be at least 100 feet or more above sea level, or at least one mile from the ocean. The State of Hawaii Emergency Management Agency has an interactive map with shelters and routes for tsunamis on Oahu, Kauai, Maui, and the Big Island.
• Realize the signs of a potential tsunami: an earthquake, a load roar from the ocean, or a sudden rising or draining of water in the ocean.
• Create a family emergency communication plan, which includes a contact off island and a high place to meet if your family gets separated.
• Have an emergency kit that includes the above items for a hurricane.
• In a tsunami, it is important to listen to authorities and evacuate immediately if told to do so.

Floods in Hawaii

In Hawaii, everyone lives in a flood zone. Floods in Hawaii happen from both the ocean and the mountain sides. The oceans will rise with the tides, including king tides, which are abnormally high tides due to the moon, causing flooding to nearby houses. Ocean swells with large waves also can produce flooding, especially during Hawaii winters. Rivers that transgress the mountains and flow to the ocean also can flood when the rains pour.

Hawaii homeowners should also note that homes in Hawaii have flood designations, which may require flood insurance to be purchased if you have a mortgage. The State of Hawaii Department of Land and Natural Resources (DLNR) manages the Hawaii flood designations.

Here are the Hawaii flood zones for properties:

• V Zones (V, VE) – High risk of flooding and is a special flood hazard area (SFHA)
• A Zones (A, AH, AO, AE) – High risk of flooding and is a special flood hazard area (SFHA)
• X and XS Zones – Low to moderate risk of flooding
• D Zones – Undetermined risk of flooding

What were some significant Hawaii floods?

On Oahu, most people will remember the October 2004 flood in Manoa. Intense rains caused the Manoa stream to overflow, and a bridge was clogged by debris in the river, creating a flood wave through residential Manoa areas and into the University of Hawaii at Manoa campus. The total damage was estimated at around $85 million with about 120 homes sustaining damage.

On the Big Island or Hawaii Island, one of the worst floods was recorded in November 2000, when rains and thunderstorms were fierce for more than 24 hours. Nearly 300 homes were destroyed or damaged and roads, bridges, and other infrastructure was destroyed, creating limited options to exit the town of Hilo and Pahala.

One of the worst floods in all the Hawaiian Islands in recent history occurred on Kauai and Oahu in April 1974. Severe storms created over $3.7 million in property damage, with the worst damage happening in the Haleiwa, Mapunapuna, and Fort Shafter neighborhoods. Hundred of vehicles and thousands of agricultural crops were destroyed. Four people died during this flood, including an infant.

How can I prepare for a flood in Hawaii?

If you are under a flood warning, it is important to find a safe shelter and evacuate if told to do so. Do not try to walk or drive through floods, as fast-moving water has a history of danger in Hawaii. Before the flood occurs, there are a number of preventative steps you can take:

• Know the flood risk for your home and business.
• Purchase flood insurance.
• Gather supplies ahead of time, like advised for a hurricane and tsunami.
• Create a plan for your household during a flood, including knowing where to go and who to contact in case a flood occurs.
• Keep your important documents in a waterproof container and also create password-protected digital copies.
• To protect your property, move valuables to higher levels and declutter drains and gutters. You might want to consider purchasing a sump pump with batteries and/or bringing sand bags around your property to prevent water from entering.

Earthquakes in Hawaii

All of the sudden the ground shakes rapidly; this is an earthquake. Hawaii is at a higher risk for earthquakes than other states in the United States; in fact, thousands of earthquakes occur every year in Hawaii, mostly due to the moving magma from Hawaii’s active volcanoes: Kilauea, Mauna Loa, Hualalai, Haleakala, and Loihi.

Hawaii also sometimes experiences tectonic earthquakes at the cross-section of Hawaii Island’s Kilauea Volcano’s south flank. The third type of earthquake that occurs in Hawaii is a mantle earthquake, in which the Earth’s crust and upper mantle bends due to the weight of the islands above.

What were the worst earthquakes in Hawaii?

Hawaii earthquake history includes a magnitude 7.9 quake in 1868 that struck the Ka‘u district of the Big Island and claimed 77 lives. Landslides as a result of the earthquake caused 31 casualties, and a tsunami from the earthquake claimed 46 lives.

The most recent fatal earthquake was a 7.2 magnitude quake, also on Hawaii Island, in 1975. This earthquake generated a tsunami that was as high as 47 feet on Hawaii Island. It caused the death of two people and around 28 injuries.

How can I prepare for an earthquake in Hawaii?

Preparing for an earthquake in Hawaii is important to do before it happens. Here are some important items to prepare for a Hawaii earthquake:

• Practice drop, cover, and hold on with family and coworkers.
• Prepare a supply kit.
• Make a family emergency communication and action plan.
• To protect your home, secure heavy items like appliances, televisions, bookcases, and pictures on the walls. Store heavy item on low shelves.
• You might want to consider purchasing an earthquake insurance policy, as a standard homeowner’s insurance policy does not cover for earthquake damage.

If an earthquake suddenly occurs, realize the best action for your location:

• Car = Pull over and stop. Set the parking brake.
• In bed = Turn face down. Cover your head and neck with a pillow.
• Outdoors = Stay away from buildings and tall trees. Move towards the mountains, if possible, due to tsunami risks.
• Inside = Stay inside and avoid doorways.

Natural Disasters and Hawaii Home Ownership: Important Information

Natural disasters do occur in Hawaii, and it is important to be prepared, especially since Hawaii is an isolated island away from other potential resources. For more information, read this comprehensive, Hawaii-specific guide from the University of Hawaii to prepare for all types of natural disasters, the Homeowner’s Handbook to Prepare for Natural Hazards.