Flood hazard map of La Trinidad (NW Nicaragua). Method and results |
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Authors: | G Furdada L E Calderón M A Marqués |
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Institution: | (1) RISKNAT Group, Dept. Geodinàmica i Geofísica, Facultat de Geologia, Universitat de Barcelona, c/ Martí i Franquès s/n, 08028 Barcelona, Spain;(2) SINAPRED, Managua, Nicaragua |
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Abstract: | During the Mitch Hurricane event (October 1998), severe floods occurred in the village of La Trinidad (Departamento de Estelí,
NW Nicaragua), which spreads at the margin of La Trinidad river. As a consequence, the need for hazard assessment and land
use planning to reduce the effects of these natural processes arose. Nicaragua is a developing country, which means that there
is a scarcity of good quality data on which to base these hazard assessments (i.e., lack of detailed topographic maps, lack
of meteorological and discharge data series). Therefore, the main objective of the present work was to generate a flood hazard
map of La Trinidad by means of a simple method, with a resulting map easy to understand and to use by the municipality for
land use planning. There is no topographic map of the area at a more detailed scale than 1:50,000. So the main document that
supports all the data and on which the final hazard map was based is the orthophotograph at 1:5,000 scale (generated from
vertical aerial photographs taken in 2000). The method used was based on classical interpretation of vertical aerial photographs
(pre Mitch and a post Mitch event), detailed field work, inquiries among the population and analysis of the main pattern of
storms occurring in the area. All these data allowed the reconstruction of different extensions and water levels corresponding
to events of different frequency and magnitude, and the qualitative association of them to three hazard levels by means of
energy and frequency. The use of orthophotographs of 1:5,000 proved to be very useful both for the development of the work
and for the presentation of the final map, because they are very easily understandable for people not trained in the interpretation
of topographic maps. |
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Keywords: | Floods Orthophotographs Hazard maps Land use planning Nicaragua |
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