Sea-level rise and the
Bangladesh and Nile deltas
James M. Broadus†
The Bangladesh and Nile deltas are often cited as among the most vulnerable regions to sea-level rise driven by greenhouse warming (IPCC 1990a, b; Jacobson 1989b; Milliman, Broadus, and Gable 1989; Titus 1986). The geographic exposure of these two deltas, high population densities, poverty, and limited ability to defend themselves against natural disaster have placed them as archetypes among the world's “worst cases” of potential global-change impacts. Closer examination of these two cases, however, makes clear not only the importance of their vulnerability but also the huge uncertainties that remain about the impacts and the complex of options for response. As such, it emphasizes the critical role of uncertainties in global environmental-risk analysis, as argued in various chapters of this volume, beginning with chapter 1.
The presumption is that global warming, driven by the build-up of greenhouse gases from human activities almost entirely outside Egypt and Bangladesh and largely in industrialized countries, will increase the volume of water in the oceans (through a combination of thermal expansion and melting ice) and lead to sea-level rises throughout the world (IPCC 1990b; USNRC 1990). The impacts of sea-level rise include inundation of low coastal lands, shoreline erosion, loss or relocation of wetlands and beaches, increased exposure to storm surge and flooding, and increased salinity of rivers and aquifers (Bird 1986; IPCC 1990b). These impacts depend on the magnitude and pace of local relative sea-level change, of which change in global sea level is only one component (the