The Application of InSAR for Satellite Based Monitoring of Dams
Todays dam owners operate in a climate where increasing attention from regulators and public tightens demands and specifications of the instrumentation, the measurements accuracy and the monitoring intervals.Further, most large dams constructed in the 1950s and 60s are rapidly approaching their estimated design life.In the northern climate of Scandinavia where dam sites often are located in remote areas, new tools to improve efficiency and performance of dam surveillance, while lowering costs, are of interest.Traditionally general monitoring of deformations in dams is done manually using leveling instruments.In recent years however the rapid progress in satellite and data processing technology, with ever increasing accuracy in satellite positioning of objects on the ground surface, has opened up the possibility of satellite based deformation monitoring of dams.One of these methodologies is InSAR (differential Interferometric Synthetic Aperture Radar), which has matured into operational use during the last decade.The InSAR technique is based on comparing two radar images, taken at different times, to observe surface deformation with accuracy on the mm to cm scale.The spatial resolution of current, high-resolution, satellites is down to 1 m.The method of satellite-based monitoring can be particularly useful in remote areas where access is an issue, or when the deformation takes place in larger areas-thereby making measurements from benchmarks complicated.Experience from applying remote sensing to Danm Safety is limited, but a recent pilot study covering Svartevann Dam in Norway (Voege, Frauenfelder, Larsen, 2012) , have promising results.Based on this Norwegian trial it became obvious that the InSAR method has potential for long-te.rm monitoring of deformation in dams.To further validate the ability of the method to correctly monitor vertical deformations in dams, the 125 meter high embankment dam at Tr(a)ngslet in Sweden has been the subject of a trial in 2012, where InSAR was used to verify the dam s vertical deformation pattern using historical data.The historical records of vertical discplacement measurement in this dam stretches all the way back to 1961, but images from 1993 ~2000 were used to model historical settlement during parts of a hiatus in this regular monitoring program from 1988 ~2003, for which there are no records.The study thus verified the effectiveness of applying satellite monitoring to dam safety,while at the same time collecting historical data to fill the monitoring hiatus.The result from the satellite images shows a clear trend for the sampled points, where the remote sensing data falls in line with the established trend.This highlighted divergences in the more recent historical records, which indicated significant divergences between recorded and calculated displacement.The divergences in the manual data recorded after the hiatus is most likely related to multiple changes of benchmarks during the lifetime of the dam, in addition to the focus on relative displacement between instrumentation readings and not on absolute displacement since the completion of the dam.Another contributing factor is that the older readings were only carried out sporadically and not being related to the reservoir s water level, which may influence the displacement-in particular horizontal, especially during large reservoir regulation amplitudes.The findings are that the accuracy and resolution of InSAR indeed appear to be sufficient for monitoring of vertical displacements in dams,and that the method is cost competitive with traditional measurements in regard of area monitored.
dam Safety monitoring displacements satellite surveillance settlements radar remote sensing
(o)yvind E Lier Ingvar Ekstr(o)m Yngvar Larsen Tom R Lauknes
Sweco, Box 34044, 100 26 Stockholm, Sweden Sweco, Box 34044, 100 26 Stockholm, Sweden.ingvar Norut, P.O.Box 6434 Forskningsparken,NO-9294 Troms(o), Norway, yngvar Norut, P.O.Box 6434 Forskningsparken,NO-9294 Troms(o), Norway, tom.rune
国际会议
昆明
英文
441-450
2013-11-01（万方平台首次上网日期，不代表论文的发表时间）