Environmental Engineering Reference
In-Depth Information
Flandrian
sea levels, rising some 110-130 m between 15 ka and 5 ka BP, drove
sediment landward. The mid-Holocene end to this
transgression
limits future beach
nourishment from this source, even with modest further sea-level rise.
All sediment movement is subject to general rules set out in Chapter 14. The breaking-
wave zone forms a seaward barrier to coarse sediment transfers except
Figure 17.6
A coastal sediment budget.
COASTAL MANAGEMENT AND SEA-LEVEL RISE
human impact
The 2001 forecasts of global sea-level rise by AD 2100 have been revised downwards
slightly by the IPCC, to between 0·09-0·88 m for the period AD 1990-2100. This has
occurred despite substantial upward revisions in forecast temperatures, the principal
cause of sea-level rise, as a result of improved modelling of glacier responses. Glacier
melt is forecast now to be partially offset by precipitation increases and the fact that low
ice-volume alpine glacial systems respond first. Increased water demand, reducing water
return to the oceans, and delta subsidence will also restrict rise (Figure 1). Thermal
expansion, therefore, forms the principal source of initial rise and will continue for
several centuries because of the slow response time of ocean temperatures, even if
greenhouse emissions are stabilized. Other climate change impacts on sea level help to
explain why the assumption of global uniform rise is a myth. Warmer ocean waters
expand faster than colder waters and regional differences in salinity and circulatory
systems maintain slight differentials.
