Combination of Space and Terrestrial Surveys in Deformation Monitoring of Dykes

Since 1984, under a contract agreement with Maraven petroleum company in Venezuela, the Department of Surveying Engineering at the University of New Brunswick (UNB) in Canada, has been involved in monitoring and analysing ground deformations in oil fields along the east coast (Costa Bolivar) of Lake Maracaibo.
Oil extraction from a comparatively shallow (300 m to 1000 m) reservoir, produces significant ground subsidence over an area of about 2000 km2. In some places, the rate of subsidence reaches 0.2 m/yr. Since 1926, several subsidence basins have been created in the area with a total maximum subsidence of about 5 min some of them. As the original terrain consisted of swamps barely above lake level, dykes and drainage systems had to be built to protect these areas against flooding [Murria and Abi-Saab 1988]. Presently, the total length of earth dyking is over 40 km with heights exceeding 7 min the areas of maximum subsidence. The safety of the dyke is of national importance, therefore, considerable attention is paid to monitoring both the dyke deformation and the ground subsidence.