Vol. 7, No. 2, 92-104, 2008
Paula Redweik, Fernando Marques and Rita Matildes
Abstract
Sea cliff retreat is mainly caused by the
occurrence of landslides of different types and dimensions, which are a
significant constraint for human activities and a source of considerable
natural risk. With the increasing use of cliffy coastal areas in recent
decades, mainly with urban areas and leisure resorts, this problem has growing
importance in many areas of the world, in terms of natural risk reduction and
of related environmental, landscape and heritage preservation issues.
The Algarve cliffs were subject of detailed studies based on systematic comparison of aerial photos from 1947 to 1991 performed with simplified methods. The inventory built with the gathered information provided a very rich database allowing the cliff retreat to be modelled, but it did not help to assess the measurement errors involved. To set up methods for cliff instability identification and measurement with the required accuracy, a photogrammetric study was made in the 16 km long Burgau-Lagos cliff-dominated coast in southern Algarve in order to achieve 3D results of the morphology changes. Several aerial surveys covering the area are available having different dates, scales and quality. The available complementary information includes camera calibration certificates for the more recent surveys and a set of ground control points identifiable in the 2002 flight.
First results of this study made it possible to establish a reference status of the coast based on the ground control information of 2002. Several events that were already mentioned in the inventory dating from 1991 were correctly detected, as well as new events occurred in the period 1991- 2002.
Submitted: 13 Feb 2008
Revised: 10 Aug 2008
Accepted: 18 Aug 2008
Published: 16 Sept 2008
Responsible editor: Jacques Populus Citation
Redweik P, F Marques & R Matildes, 2008. A strategy for detection and measurement of the cliff retreat in the coast of Algarve (Portugal) by photogrammetry. EARSeL eProceedings, 7(2): 92-104
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EARSeL European Association of Remote Sensing Laboratories, Strasbourg, France |
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BIS-Verlag |