Field trip report on the development of national tsunami plans in Colombia and Ecuador, August 2002 by Emilio Lorca Mella, Servicio Hidrográfico y Oceanográfico de la Armada, Chile
During the XVIII Session of ICG/ITSU an agreement was reached regarding the visit of a tsunami consultant from Chile to go to Colombia and Ecuador to help developing Tsunami Mitigation Plans and Strategies for Tumaco (Colombia) and Esmeraldas (Ecuador). This visit was performed August 10 to the 25th, 2002.
Tumaco is a set of three small and low barrier islands located over the southern part of the Pacific coast, close to the border with Ecuador, over the subduction zone of the Nazca plate under the South American plate. Four big earthquakes during the 20th century have generated tsunamis. The last one in 1979 (magnitude 7.9) produced 2.5 meters waves and about 200 victims in surrounding villages. The northern coastline of Tumaco was locally inundated, shallowly flooding a number of houses. The highest wave rose only about 0.8 m above the former high-tide position. Tsunami damage would have been greater had the waves not arrived at the lowest tide.
Around 80,000 people live on the islands, most of them concentrated on one of them. Two narrow bridges link the islands with the mainland. There is no question about the potential risk of the region and the need of undertaking actions to mitigate the effects of the imminent attack of the next tsunami in the Bay of Tumaco.
A one-day tour around the islands was the first activity upon arrival to the area to get familiar with situation.
A Workshop was organized to work with the local emergency committee. The name of the workshop was “Iniciativas para la Consolidación de un Sistema Local de Respuesta Efectivo en caso de Tsunami (First Steps to Consolidate an Effective Local Response System in case of Tsunami).
All the local emergency agencies represented in the city and representatives of some private enterprises actively participated in the workshop, after answering a questionnaire previously distributed to show their potential and needs to face an emergency situation as a tsunami impact. Agencies participating were: City Hall, Police, Navy, Civil Defence, Fire Department, Red Cross and Hospital. Also represented at the workshop were agencies that are part of the National Tsunami Warning System; namely OSSO (Seismic Observatory), INGEOMINAS (Mining Engineering) and CCCP (Navy Pollution Control Centre).
On Monday 12 of August a formal meeting with the representatives of the National Tsunami Warning System was held to coordinate the activities and strategies within the workshop.
The Workshop was opened on the 13th of August by the representative of the Major of Tumaco, Mr. Marino Oliva who stressed the importance of the workshop for the future of the city. As an introduction to the session, a revision of the work already done was presented by Captain Carlos Tejada, Director of the CCCP. He also explained the objectives for the Workshop, namely to unify criteria around the role of every institution within the tsunami response activities and to get a preliminary evacuation plan. There was also a presentation regarding the scheme of the National Tsunami Warning System. Next, a presentation was done regarding the Chilean experiences in the operation of the National Tsunami Warning System and in the implementation of Local Tsunami Emergency Procedures. The work of the day was ended with the analysis of some of the responses to the questionnaire previously distributed.
The workshop continued on the 14th of August with three round tables analysing the following items: (!) Most probable tsunami scenario; (2) Possible evacuation procedures and (3) Warning modes.
(1) Most probable tsunami scenario: after a revision done on the seismic history of the area, it was decided to take into account the worst case scenario, meaning an 7.9 earthquake occurring in front of Tumaco at high tide.
(2) Possible evacuation procedures: after a revision of the results of the computer tsunami simulation done for the worst case scenario, it was determined that in the security areas there is room enough at every island to concentrate the people without evacuation through the narrow bridges.
(3) Warning modes: the numerical simulation done for the worst case scenario gave a tsunami travel time to Tumaco coast of 30 minutes. With this time lag there is no possible way of setting a local warning mode. It was decided that the best way to get a proper response during a tsunami emergency was to educate the people to recognize a big earthquake and proceed with the proper evacuation actions.
On the 15th of August the work was concentrated in setting the activities for the structure of the Evacuation Plan. Security areas as well as evacuation routes were discussed and defined.
On the last day of the visit, homework was given for each of the local emergency agencies represented at the workshop to develop their own particular plans under the general one, which will be discussed and integrated into the final comprehensive Tumaco Evacuation Plan.
The work done here was completely different than at Tumaco, since actual conditions of the National Tsunami Warning System is far from being in a good stage to initiate actions for a local tsunami warning system at Esmeraldas. The activities were concentrated at INOCAR (Oceanographic Institute of the Navy) in Guayaquil where I worked with the lady in charge of the Tsunami Program.
No tsunami simulation have been done for Esmeraldas, which was impacted by the same tsunami than Tumaco in 1979. The software exists, so I recommended to do it as a first stage to start working with the local emergency authorities.
Esmeraldas is a port with around 200,000 inhabitants located in the northern coast of Ecuador, close to the border with Colombia and located at the mouth of Esmeraldas river. There are very good facilities as broad streets, good communications by phone, good roads and the like. However, around 15% of the city is located close to the river at low altitudes. A big tsunami impact should be expected at these places.
The first three days at INOCAR were dedicated to give a comprehensive plan of action for the near future starting with the proper calculation of the tsunami risk at Esmeraldas through the use of the numerical simulation to get the Inundation Map to start with. A complete list of requirements to do this job was given and a list of actions with the Local Emergency Authorities was set in order to conform a Local Tsunami Emergency Team.
On the last two days, a trip by road to Esmeraldas was organized to get in touch with the Navy Port Authority, captain Daniel Donoso Velasquez. An account of what should be expected to do was given to him during a short interview. He is also the Head of an Environment Impact Committee where the local tsunami awareness activities could be focalised. I recommended to use it as a very good tool since most of the local emergency agencies are represented.
VALPARAISO, September 11, 2002
Emilio Lorca Mella
Servicio Hidrográfico y Oceanográfico de la Armada