Abstract

MATURANA CORDOBA, Zamir. Flood-threat zoning map of the urban area of Chocó (Quibdó): A study based on interpreting radar, satellite and aerial photograph images. Ing. Investig. [online]. 2007, vol.27, n.3, pp.24-34. ISSN 0120-5609.

A zoning map of areas which flood due to the Atrato River and its tributaries (the Cabí, Caraño and Yesca) overflowing in the urban area of Chocó (Quibdo) was drawn up to be used by aid authorities and Quibdó city as a planning and control tool. This research relied on CIAF (Centro Interamericano de Fotointerpretación) support and assessment. This entity is a subsidiary institution of the Instituto Geográfico Agustín Codazzi which provided their installations and the required geographical material. This research was initially based on interpreting radar (INTERA), satellite (LANDSAT) and aerial photographic images; this was verified by field verification of the interpreted data. Other variables such as climatic, geological, temperature, topographic conditions, historic and hydrological series and facts regarding the region were studied as additional information required for drawing conclusions. Aerial photographs provided the most reliable images due to their scales, quantity and quality and the date of when they were taken. Radar images (INTERA) were also important when visually analysing a sector’s topography as they were produced by an active microwave sensor (totally eliminating climatic obstacles). On the contrary, satellite images did not have great relevance due to the amount of clouds hampering any kind of analysis. Complementing these results, a calibration curve for analysing this section’s maximum flow values was based on historical series data regarding the Atrato River’s flows and maximum levels recorded at the Quibdo hydrographical station and the river-bed’s cross-section. Implications that the river would overflow or has overflowed were statistically estimated on these results, thereby setting the limits (supported by cartographic data) for the corresponding areas at risk of flooding. A map marking areas at risk of flooding in the urban zone of Quibdó was then designed and a document prepared concluding that neighbourhoods on land lying at 25-27 metres above sea-level (or less) and located near the banks of the Atrato river and its tributaries are considered as being mid- high-flood threat areas, having 5-20 and 50-100 year return periods, respectively.

Keywords : flood-threat zoning; radar image; satellite image; aerial photograph; topographic map; calibration curve; stream; Atrato river.

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