The flood hazard caused by Atrato River in Quibdó, northwest of Colombia is assessed using statistical modeling techniques (Gumbel and GRADEX), hydraulic modeling with HEC-RAS and the Geographic Information Systems (GIS). Three flood hazard maps for return periods of 10, 20 and 50 years are generated. The flood hazard modeling reveals that the flooded zone is more significant out of the left (West) bank than out of the right (East) bank of Atrato River. For the three return periods the maximum depth of water reached by the river and extent of flooding are estimated. Sensitivity analysis on roughness coefficient and peak discharge is performed. For 50 year return period (Q = 3054 m 3 /s), water depth on the left and right bank of Atrato River is 3.7 m and 3.1 m, respectively. This information is useful in defining the minimum height of flood protection structures such as dikes to protect the area from flooding. The results can be useful for evacuation planning, estimation of damages and post flood recovery efforts.
We compare country risk rankings derived from two recently published global disaster risk analyses. One set of country rankings is based on the Disaster Risk Index (DRI) developed by the United Nations Environment Program (UNEP) Division of Early Warning and Assessment Global Resource Information Database project under a contract to the United Nations Development Program (UNDP). The other is based on an index of disaster mortality risk developed by the Global Natural Disaster Risk Hotspots project implemented by Columbia University, the World Bank and associated partners. We convert data from these sources into two comparable indexes of disaster mortality risk and rank countries according to the resulting values for a set of natural hazards common to both studies. The country rankings are moderately correlated, ranging from .41 to .56 for individual hazards to .31 for multi-hazard mortality risks. We identify the top 25 countries according to the mortality risk values we recomputed from each study's results to show the degree to which countries are highly ranked in common. The numbers of countries common to both lists for individual hazards range from 7 to 16 out of 25. The correspondence among the top 25 ranked countries is lowest for earthquakes and floods. Only 6 out of 25 countries are common to both lists in the multi-hazard case. We suggest that while the convergence in the results for some hazards is encouraging, more work is needed to improve data and methods, particularly with respect to assessing the role of vulnerability in the creation of risk and the calculation of multi-hazard risks.
The macroseismic intensity of the 18 October 1992 Murindo-Atrato earthquake that\ud affected the northwestern states of Colombia (Choco´ and Antioquia) is reassessed using the\ud newly developed INQUA Environmental Seismic Intensity Scale (ESI 2007) which is based on\ud the evaluation of earthquake environmental effects. To generate the ESI 2007 isoseismal map of\ud northwestern Colombia, a geographical information system was used. Unifying the available\ud information on the seismological and active tectonics framework including historical seismicity,\ud hypocentral depths, foreshocks, aftershocks, focal mechanism, macroseismic data under the\ud same GIS and the map of Quaternary faults allowed us to reinterpret the geological and environmental\ud effects of the 1992 earthquakes sequence. A total of 24 sites from the areas of Quibdo´ ,\ud Bojaya´, Rio Sucio, Murindo, Vigı´a del Fuerte and Turbo were evaluated. A systematic comparison\ud among evaluated intensities (Modified Mercalli and ESI scale) revealed differences from one to\ud two degrees. According to the ESI 2007 scale, the epicentral intensity Io is XI. This represents\ud one degree higher than the epicentral intensity obtained using MM and Medveded Sponhauer\ud Karnik (MSK) intensity scales, probably due to the lack of suitable observations on building\ud damage in this poorly populated and developed region. This information is also useful in order\ud to shed some light on the persistent question of the exact location and dimension of the main\ud rupture zone associated with the earthquake. The isoseismal map derived from the integration of\ud the whole set of environmental effects with other macroseismic data strongly suggests that the causative\ud tectonic structure is the Murindo fault. However, the rupture length derived from the distribution\ud of ground effects is greater than the Murindo fault length, implying that other nearby fault\ud segments were activated during the 1992 event. The new isoseismal map resulting from this work is\ud relevant for the assessment of future seismic risk in the northwestern region of Colombia. Overall,\ud the application of the ESI 2007 scale to the 18 October 1992 earthquake, and to similar strong\ud events in the region, can be useful for disaster management and planning, estimation of damage,\ud and post-earthquake recovery efforts
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