| dc.description |
Land subsidence and coastal erosion are worldwide problems , particularly in
densely populated deltas . The Nile Delta is no exception . Currently , it is undergoing land
subsidence and is simultaneously experiencing retreat of its coastline . The impacts of
these long -term interrelated geomorphic problems are heightened by the economic ,
social and historical importance of the delta to Egypt . Unfortunately , the current
measures of the rates of subsidence and coastal erosion in the delta are rough estimates
at best . Sustainable development of the delta requires accurate and detailed spatial and
temporal measures of subsidence and coastal retreat rates .
Radar interferometry is a unique remote sensing approach that can be used to
map topography with 1 m vertical accuracy and measure surface deformation with 1 mm
level accuracy . Radar interferometry has been employed in this dissertation to measure
urban subsidence and coastal change in the Nile Delta . Synthetic Aperture Radar (SAR )
data of 5 .66 cm wavelength acquired by the European Radar Satellites (ERS -1 and ERS -
2 ) spanning eight years (1993 -2000 ) have been used in this investigation . The ERS data have been selected because the spatial and temporal coverage , as well as the short
wavelength , are appropriate to measure the slow rate of subsidence in the delta . The ERS
tandem coherence images are also appropriate for coastal change detection .
The magnitude and pattern of subsidence are detected and measured using
Permanent Scatterer interferometry . The measured rates of subsidence in greater Cairo ,
Mansura , and Mahala are 7 , 9 , and 5 mm yr -1 , respectively . Areas of erosion and
accretion in the eastern side of the delta are detected using the ERS tandem coherence
and the ERS amplitude images . The average measured rates of erosion and accretion are
-9 .57 and +5 .44 m yr -1 , respectively . These measured rates pose an urgent need of
regular monitoring of subsidence and coastline retreat in the delta .
This study highlighted the feasibility of applying Permanent Scatterer
interferometry in inappropriate environment for conventional SAR interferometry . The
study addressed possibilities and limitations for successful use of SAR interferometry
within the densely vegetated delta and introduced alternative strategies for further
improvement of SAR interferometric measurements in the delta . |
|