Sea Level Rise

The implications of rising sea levels in the Skagit region are critical because the Skagit delta is in a low-lying area near sea level.  Rising sea levels place pressure on dikes, reduce gravity fed drainage of agricultural lands, increase flood implications for Mt. Vernon and the other small cities, and affect other infrastructure and homes.

The Intergovernmental Panel on Climate Change (IPCC) has published global projections of sea level rise. However translating the global projections of sea levels into local projections for the Puget Sound hinge on multiple local factors, like atmospheric circulation patterns and vertical land movement.  For instance in Puget Sound the Olympic Peninsula shorelines are rising whereas the Skagit delta shorelines are sinking.

Converting the IPCC projections for sea level rise by accounting for local factors, estimates for the Puget Sound region range from about 6 inches for the low emissions scenario to about 50 inches for the highest emissions scenario. Due to the fact that the delta is sinking, relative sea level rise may be greater in the Skagit areas than in other parts of Puget Sound.

Recent work by Dr. Grossman and Roger Fuller provides information showing where flooding would occur under current mean higher high water and a typical winter storm surge if dikes and levees did not hold Puget Sound back.  Their work also shows projections at year 2050 and 2100 if dikes were not present given the best available science projecting future sea level rise.  These scenarios illustrate the potential risk if dikes or levees were to fail or overtop.  Dr. Grossman and Roger Fuller plan to complete their Skagit modeling by the end of 2012.

The science underpinning global sea level rise projections and estimates of local impacts are rapidly evolving, and more recent studies indicate higher rates of global sea level rise than those discussed above.