Storms, storm surges, tsunamis, swell, seiche, sea level rise, freak waves, tidal motion may have extreme characteristics sometimes. Those should be investigated, monitored, modeled, observed, forecasted and necessary precautions can be developed for reduction of risk and safety of coastal communities.
A disaster is a sudden, calamitous event that seriously disrupts the functioning of a community or society and causes human, material, and economic or environmental losses that exceed the community’s or society’s ability to cope using its own resources. A disaster occurs when a hazard impacts on vulnerable people. The combination of hazards, vulnerability and inability to reduce the potential negative consequences of risk results in disaster. Disaster Management can be defined as the organization and management of resources and responsibilities for dealing with all humanitarian aspects of emergencies, in particular preparedness, response and recovery in order to lessen the impact of disasters. The first people to respond to a disaster are those living in the local community. They are the first to start rescue and relief operations. The Red Cross and Red Crescent National Societies therefore focus on community-based disaster preparedness, which assists communities to reduce their vulnerability to disasters and strengthen their capacities to resist them. When the capacity of a community or country to respond and recover from a disaster is overwhelmed, and upon request from the National Society, the International Federation uses its regional and international networks, assets and resources to bring assistance to the communities and National Red Cross Red Crescent Society which is assisting them. At an international level the International Federation advocates with Governments, international organisations and humanitarian donors for better practice and accountability in disaster management and greater respect of the dignity of the vulnerable people.
The United Nations Office of Disaster Risk Reduction UNISDR develop basic definitions on disaster risk reduction to promote a common understanding on the subject for use by the public, authorities and practitioners. The terms are based on a broad consideration of different international sources. The terminology is available at; https://www.unisdr.org/we/inform/terminology
1) How Oceans Behave Oceans cover about 70% of the Earth's surface. The oceans contain roughly 97% of the Earth's water supply. The ocean appears blue because it is reflecting the blue colour of the sky. The oceans of Earth serve many functions, especially affecting the weather and temperature. They moderate the Earth's temperature by absorbing incoming solar radiation (stored as heat energy). Moving ocean currents distribute this heat energy around the globe. This heats the land and air during winter and cools it during summer. The Earth's oceans are all connected to one another. Until the year 2000, there were four recognized oceans: The Pacific, Atlantic, Indian, and Arctic. In the spring of 2000, the International Hydrographic Organization delimited a new ocean, the Southern Ocean (it surrounds Antarctica and extends to 60 degrees latitude). 2) Wave Behaviour in Shallow Water Waves moving out away from a storm eventually organize themselves into a swell, and eventually, if they are not destroyed by interference, they reach the shore. The seafloor shallows as the waves approach shore, and eventually the waves touch bottom (they reach wave base). At this point we shift from "deep water" to "shallow water" (from the wave's perspective). The waves begin to slow down (celerity decreases) due to friction and wave celerity now depends on water depth. So as the waves come to shore from the sea,
- they change from deep-water waves to shallow water waves at wave base, where water depth = 1/2 wavelength,
- wavelength decreases, period stays the same
- height increases
- wave breaks and becomes
- swash, then backwash
1) Tsunami Tsunami is the Japanese word for harbor (tsu) wave (nami). Tsunami is a series of very large waves generated by an underwater disturbance: a submarine earthquake, a submarine landslide, a volcanic eruption or a meteorite. Tsunamis are very long waves. Due to their long wavelength, the distance between two crests may reach 100 km. The speed of a tsunami wave depends on ocean depth, therefore they travel faster in deep ocean and they slow in shallow waters. Tsunamis may travel very fast in deep ocean, as fast as a jet plane. Although, in deep ocean tsunami height does not exceed a few meters when they approach the coast and enter shallow waters they slow down but their height increase. The morphology of the ocean floor and of the coastline will influence the size of the wave. Tsunamis are different from wind waves, that we may observe on the beach. When tsunamis flood coastal areas they can penetrate large distances inland (more than 1 km); when the waves retreat they carry large objects, people and debris. A tsunami is not a single wave but a series of waves. Tsunamis can occur at any time, there is no tsunami season! Do you know?
- The Indian Ocean tsunami on 26 December 2004 in Indian Ocean claimed more than 230 000 lives throughout the Indian Ocean coast
- That there are natural warning signs of a possible tsunami: the earthquake itself- if you feel an earthquake near the coast you must evacuate towards higher ground; Sometimes tsunami arrival is preceded by a noticeable fall in sea level as the ocean retreats seaward exposing the seafloor.
- A tsunami occurred after the 1999 Ismit earthquake in Turkey. At Tavsancil, the sea in the local port receded first and when the sea came back it flooded the first floor of some hoses
- Central Presssure (Lower pressure will produce a higher surge)
- Storm Intensity (Stronger winds will produce a higher surge)
- Size (Larger storm will produce higher surge)
- Angle of approach to coast
- Shape of the coastline
- Width and Slope of the Ocean Bottom
- Local Features