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A recurring threat: floodwaters in Tumbes, Peru (Photo: PCI-Geomatics)
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Landslide risk on Guatemala City's slopes
(Photo: Int'l Land Systems, Inc.)
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Evidence of El Niņo's destructive power could be seen all along Peru's northern coast last February, but it was impossible
for disaster management officials at the Instituto Nacional de Defensa Civil to determine the exact extent of the flooding. The
IDB proposed a demonstration project to see if satellite imagery and GIS methods could be used for this purpose. Canadian
consulting firm PCI-Geomatics produced the maps (See pictures-sequence on left first icon) by superimposing images taken by
two satellites: the U.S. Landsat and Canada's RADARSAT. The latter satellite is equipped with a synthetic aperture radar than
can "see through" thick cloud cover--a crucial capability since most of Peru was overcast during the flooding. In the resulting
image, (first photo from the left), flood waters around the city of Tumbes, near the Ecuadorian border, are visible as dark areas
on Februay 10. The second image (on the right side), taken on March 6, shows changes along the edges of local floodplains
after the waters receded. Image processing experts subsequently produced maps showing the exact extent of the damage and
indicating which roads, bridges, pipelines and neighborhoods will be at risk in the future. In earthquake-prone Guatemala,
landslides pose a constant threat. So when the government launched an IDB-financed program to provide low-cost housing loans
to families in Guatemala City, municipal officials wanted to make sure they did not pay to build houses on slopes that were at
high risk of a landslide. Classifying each of the hundreds of hillsides already under development in the metropolitan area
would have been hugely expensive. But by creating a GIS that combined a detailed satellite image with data on existing housing
use, bedrock geology, and areas damaged in the infamous landslides of 1976, consultants from International Land Systems Inc.,
were able to quickly produce the map displayed on the left (second icon on the left). Areas shaded in red are considered to be at
high risk of landslides; blue represents medium risk. Red areas are excluded from future development. People wanting to build in
blue areas could still obtain a loan, but they had to build retaining walls and other safeguards.
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