Historical Urban Landscape as a Descriptive Feature for Risk Assessment: the ‘Quebradas’ of Quito

Abstract:

Over the last decades the city of Quito has undergone notable spatial transformations, most of which have not been recorded given the unplanned nature of the city’s growth. Amongst the various unplanned changes that have shaped the modern Quito, the filling of ravines or ‘quebradas’, is one of major concern due to the numerous hazardous events associated to it. Determining the exact location of these areas and assessing their extent is therefore crucial for the city development planning. This paper assessed the potential of historical cartography and aerial photography to document urban landscape change and to determine risk areas in a digital geospatial environment. Historical planimetric cartography (1932) and aerial photography (1956) were rectified using a DLT Geometric Correction Model in order to reconstruct the historical urban landscape of Quito and locate ancient ravines or ‘quebradas’ which have been filled over the last century. The results show that the DLT Geometric Correction Model performed by ERDAS v10 renders high accuracy raster coverages from historical cartography which can be efficiently used in change detection. This study also emphasizes the importance of historical cartographic documents as the sole source of reliable information on urban historical landscape before aerial photography and the need for making this information available also in a vector format to government and academic institutions for decision making and research purposes.

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