Date of Award
Doctor of Philosophy
Dr. Mohamed Sultan
Dr. Alan Kehew
Dr. Michelle Kominz
Dr. Richard Becker
Many of the deltas of the world are experiencing land deformation, subsidence or uplift of landmass, due to natural or anthropogenic causes, or a combination of both processes and causes. These deltaic settings are densely populated and border some of our world’s largest water bodies (oceans and seas). The land deformation, especially the subsidence component, when combined with the climate change-induced sea level rise, coastal erosion, and other anthropogenic drivers, will undoubtedly impact the population and economy of coastal areas of deltas. For the Nile Delta of Egypt, the land deformation processes and the factors that control the deformation processes were investigated using an integrated approach (remote sensing, geology, hydrogeology, and geodesy). Moreover, the impact of sea level rise and land deformation on the coastal areas and communities was assessed by simulating sea encroachment scenario and measuring ongoing deformation.
Persistent scatterer interferometric analyses were conducted on a stack of 84 Envisat ASAR scenes spanning 7 years (2004 to 2010) over the entire Nile Delta of Egypt and surroundings (area: 40,416 km2) to monitor the ongoing spatial and temporal land deformation,identify the factors controlling the deformation, and model the interplay between sea level rise and land subsidence to identify areas and populations threatened by sea encroachment by the end of the 21st century. Findings include: (a) general patterns of subsidence (average rate: −2.4mm/yr) in the northern delta, near-steady to slight subsidence in the southern delta (average rate: 0.4 mm/yr), separated by a previously mapped flexure zone (minimum width: 20–40 km) undergoing uplift (average rate: 2.5 mm/yr); (b) high subsidence rates (up to −8.9 mm/yr) over the north-central and northeastern delta (area: ~4815 km2), possibly due to compaction of recent(old), thick (>5m) silt and clay-rich Holocene sediments; (c) the terminus and bifurcation points of the now defunct distributaries of the Nile where thick accumulation of compressible sediments are anticipated also show high subsidence rates (up to −7.8 mm/yr); the paleo-distributaries were delineated using high-resolution digital elevation model (10 m horizontal resolution) extracted from 195 high-resolution (1:25,000 scale; 0.5 m contour interval) topographic map sheets, ; (d) high subsidence rates (up to −9.7 mm/yr) in areas where the highest groundwater extraction rates were reported in southern delta (Menoufia governorate) and in reclaimed desert land in the western delta (Beheira governorate); (e) high subsidence rates (up to −9.7 mm/yr) over onshore gas fields, notably the Abu Madi gas field, where high gas extractionrates have been recorded; (f) using extracted deformation rates, high-resolution TanDEM-X digital elevation model, a eustatic sea level rise of 0.4 m, and applying a bathtub inundation model, an estimated 2660 km2 in northern delta will be inundated by year 2100.
Gebremichael, Esayas Gebrekidan, "Assessing Land Deformation and Sea Encroachment in the Nile Delta: A Radar Interferometric and Modeling Approach" (2018). Dissertations. 3371.