SEA-LEVEL RISE AND COASTAL CHANGE HAZARDS: IMPLICATIONS FOR THE FUTURE UNDER CHANGING CLIMATE

Observations show that the increase in global temperature is unequivocal; and, there is consensus in the scientific community that the warming and wide-spread environmental changes are primarily the result of the rapid increase in greenhouse gas emissions from fossil fuel burning since the late 19th century. One of the most significant climate-change impacts of the upward trend in global temperature is sea-level rise (SLR). Direct SLR impacts include: increased coastal erosion, more frequent storm-surge flooding, inundation of low-lying areas, saltwater intrusion into aquifers, wetland loss, and threats to human infrastructure in coastal zones. Recent climate-change assessments, such as IPCC (2007), CCSP SAP 4.1 (2009), USGCRP (2009), and IARU Congress (2009), suggest sea level is likely to rise by 0.5 to 1 m or more by year 2100; and, possibly much more due to climate processes that appear to be more dynamic than previously thought (e.g., Greenland and West Antarctica ice-sheet melting, ocean current disruptions). Further, some climate scientists suggest that highly accelerated melting in Greenland and West Antarctica could lead to SLR of about 5 m over the next several hundred years.

Accelerated SLR will have significant impacts on coastal systems, natural resources and habitats, and societies world-wide. Coastal scientists have well-established conceptual and qualitative frameworks based on field studies and modeling regarding the primary factors and processes that drive coastal change. Current techniques used to predict coastal change, however, can not at present provide reliable long-term quantitative predictions at spatial and temporal scales needed for detailed coastal planning.

With substantial acceleration of SLR, “traditional” coastal management and engineering practices (i.e., protecting and maintaining shoreline position with hard structures, beach nourishment) will become more difficult for society and may not be economically or environmentally sustainable for many coastal regions. Predicted accelerated rates of SLR need to be fully considered in coastal management plans and engineering design. Options such as strategic relocation of infrastructure to higher elevation and conversion of low-lying developed areas to open space may be more appropriate in managing for and adapting to future coastal change.