noun ( pl. same or -mis ) a long high sea wave caused by an earthquake, submarine landslide, or other disturbance. ORIGIN late 19th cent.: from Japanese, from tsu ‘harbor’ + nami ‘wave.’
Tsunami are sometimes referred to as tidal waves. In recent years, this term has fallen out of favor, especially in the scientific community, because tsunami actually have nothing to do with tides. The once-popular term derives from their most common appearance, which is that of an extraordinarily high tidal bore. Tsunami and tides both produce waves of water that move inland, but in the case of tsunami the inland movement of water is much greater and lasts for a longer period, giving the impression of an incredibly high tide. Although the meanings of “tidal” include “resembling” or “having the form or character of the tides, and the term tsunami is no more accurate because tsunami are not limited to harbours, use of the term tidal wave is discouraged by geologists and oceanographers.
Tsunami Preparedness in Oregon
The principal generation mechanism (or cause) of a tsunami is the displacement of a substantial volume of water or perturbation of the sea. This displacement of water is usually attributed to either earthquakes, landslides, volcanic eruptions, or more rarely by meteorites and nuclear tests. The waves formed in this way are then sustained by gravity. Tides do not play any part in the generation of tsunamis.
Tsunami generated by seismicity Tsunami can be generated when the sea floor abruptly deforms and vertically displaces the overlying water. Tectonic earthquakes are a particular kind of earthquake that are associated with the Earth’s crustal deformation; when these earthquakes occur beneath the sea, the water above the deformed area is displaced from its equilibrium position. More specifically, a tsunami can be generated when thrust faults associated with convergent or destructive plate boundaries move abruptly, resulting in water displacement, owing to the vertical component of movement involved. Movement on normal faults will also cause displacement of the seabed, but the size of the largest of such events is normally too small to give rise to a significant tsunami.
1. EMERGENCY ALERT SYSTEM (EAS)
-KCST Radio 106.9 FM -Network TV Channels
2. NOAA WEATHER RADIO
-Channel 162.500 -Lane County S.A.M.E Code: 041039
3. FLORENCE AREA SIREN TONES
Test: 60 sec. steady tone Last Friday of month at 11:00 a.m. Warning: Wailing tone varying from high to low warble tone EVACUATE IMMEDIATELY from beaches and inundation zone All Clear: Westminster Chimes – Safe to return home
4. AUTOMATED TELEPHONE CALLS
To homes in inundation zone only
For tsunamis generated near the Oregon Coast 1. Dramatic Change in Sea Level at the Beach Those residents in the inundation zone are to immediately Evacuate on Foot to high ground or to designated evacuation sites along Highway 101. 2. Violent Shaking from Cascadia Subduction Zone earthquake If not in the inundation zone, Shelter-In-Place in undamaged home ONLY after all shaking stops and advised by authorities to do so.
When, where, how, what kind, how often?
- A tsunami can occur anytime of the day or year.
- It will happen in coastal communities within distance of subduction zone.
- It is caused by an undersea earthquake near or far from the Oregon coast.
- A tsunami could last up to 12 hours.
- There are two kinds of tsunamis. One is a local event (off the Oregon coast) and a distant event (an earthquake from the Oregon coast). The last event local event occurred in January 1700. In Oregon, geologists state that a local tsunami would occur every 300-500 years.
The Siren Tones
The sirens are at high-power capacity and have 2400 watts of power that cover up to a 4,000 ft radius. Optimum sound propagation conditions exist when there are no obstructions in the sound path, which means that wind speed and direction will be a prevailing factor in sound projection. The first tone is the TEST TONE, which is a long steady sound. The test tone will be activated on the last Friday of each month. It will last for a few minutes, beginning at 11 am. The test tone will be followed by the ‘all clear’ tone (see below) The second tone is the REAL TIME evacuation blast, known as a wail tone. Evacuation for a distant tsunami will generally be indicated by a siren blast and an announcement over NOAA weather radio that the local area has been put into an official TSUNAMI WARNING. The wail tone varies from a low to high warble sound. In isolated areas along the beaches and bays you may not hear a warning siren. A sudden change of sea level should prompt you to move immediately to higher ground. Should the evacuation blast be activated, first evacuate away from the shoreline areas, then turn your radio to KCST 106.9 FM for more information. The third tone is the ALL CLEAR sound, which resembles the Westminster Chimes. You will hear this tone if the tsunami warning has been cancelled. The protocols state that the ‘all clear’ will run for one minute followed by a two minute rest period. This process will be repeated five times. At that time it is ok for people to return to their homes.
What to do
- The tsunami sirens are intended to be used as a warning when a distant tsunami approaches the shoreline. The primary focus of the sirens is to warn those who are outside in the inundation zone or those who are on the beach.
- If you hear the REAL TIME evacuation tone, it is your signal to get to higher ground. There may be a window span of one to two hours for you to grab your emergency supplies and leave the inundation zone, but you must make the conscious decision ahead of time to leave the area when you hear this tone.
- If you feel the earth shaking, get to higher ground immediately and do NOT wait for the sirens. An earthquake in the Florence area is an indicator that a tsunami will reach us in 10-15 minutes.
- KCST Coast Radio 106.9 FM is the emergency broadcast station for Florence and its surrounding areas. They will provide further information on evacuations.
Floods are one of the most common hazards in the United States. The effects can be local, impacting a neighborhood or community, or very large, affecting entire river basins and multiple states. Some floods develop slowly over a period of days. But flash floods can develop quickly, sometimes in just a few minutes and without visible signs of rain. Flash floods often have a dangerous wall of roaring water that caries rocks, mud, and other debris and can sweep away most things its path. Overland flooding occurs outside a defined river or stream, such as when a levee is breached, but still can be destructive.
To prepare for a flood you should:
- Avoid building in a floodplain unless you elevate and reinforce your home.
- Elevate the furnace, water heater, and electric panel if susceptible to flooding.
- Install “check valves” in sewer traps to prevent flood water from backing up into the drains of your home.
- Construct barriers (levees, beams, floodwalls) to stop floodwater from entering the building.
- Seal walls in basements with waterproofing compounds to avoid seepage. During a Flood If a flood is likely in your area, you should Listen to KCST 106.9 FM or turn on your television.
- Be aware that flash flooding can occur. If there is any possibility of a flash flood, move immediately to higher ground. Do not wait for instructions to move.
- Be aware of streams, drainage channels, canyons, and other areas known to flood suddenly. Flash floods can occur in these areas with or without such typical warnings as rain clouds or heavy rains.
If you must prepare to evacuate, you should do the following:
- Secure your home. If you have time, bring in outdoor furniture. Move essential items to an upper floor.
- Turn off utilities at the main switches or valves if instructed to do so. Disconnect electrical appliances. Do not touch electrical equipment if you are wet or standing in water.
If you have to leave your home, remember these evacuation tips:
- Do not walk through moving water. Six inches of moving water can make you fall. If you have to walk in water, walk where the water is not moving. Us a stick to check the firmness of the ground in front of you.
- Do not drive into flooded areas.
- If flood waters rise around your car, abandon the car and move to higher ground if you can do so safely. You and the vehicle can be quickly swept away.
The following are guidelines for the period following a flood:
- Listen for news reports to learn whether the community’s water supply is safe to drink. Avoid floodwaters; water may be contaminated by oil, gasoline, or raw sewage. Water may also be electrically charged from underground or downed power lines.
- Avoid moving water.
- Be aware of areas where floodwaters have receded. Roads may have weakened and could collapse under the weight of a car.
- Stay away from downed power lines, and report them to the power company. Return home only when authorities indicate it is safe.
- Stay out of any building if it is surrounded by floodwaters. Use extreme caution when entering buildings; there may be hidden damage, particularly in foundations. Service damaged septic tanks, cesspools, pits and leaching systems as soon as possible. Damaged sewage systems are serious health hazards.
- Clean and disinfect everything that got wet. Mud left from floodwater can contain sewage and chemicals.
- Familiarize yourself with these terms: Flood Watch. This means that flooding is possible.
- Tune into KCST 106.9 FM, your NOAA Weather Radio, or television for more information Flash Flood Watch. Flash flooding is possible.
- Be prepared to move to higher ground.
- Tune into KCST 106.9 FM, your NOAA Weather Radio, or television for more information. Flood Warning. Flooding is occurring or will occur soon; if advised to evacuate, do so immediately. Flash Flood Warning. A flash flood is occurring; seek higher ground on foot immediately.
The flood hazard risk assessment for the City of Florence indicates that the city has a high probability and vulnerability to future flooding events. The most recent flood occurred in 1996 where entire housing developments in Florence were inundated. Currently, the city is a participant in the National Flood Insurance Protection Program which covers a total of 158 properties.