Adapting to sea-level rise: relative sea level trends to 2100 for the United States

Global sea levels have slowly risen during this century, and that rise is expected to accelerate in the coming century due to anthropogenic global warming. A total rise of up to 1 m is possible by the year 2100 (relative to 1990). To deal with this change, coastal managers require site-specific information on relative (i.e., local) changes in sea level to determine what might be threatened. Therefore as a first step, global sea-level rise scenarios need to be transformed into relative sea-level change scenarios which take account of local and regional factors, such as vertical land movements, in addition to global changes. Even present rates of relative sea-level rise have important long-term implications for coastal management-projecting existing trends predicts a relative sea-level rise from 1990 to 2100 of up to 0.4 m and 1.15 m for the Mid-Atlantic Region and Louisiana, respectively. Ignoring sea-level rise will lead to unwise decisions and increasing hazard with time.This article adapts the Intergovernmental Panel on Climate Change (IPCC) global scenarios for sea-level rise (Warrick et al., 1996) to three relative sea-level rise scenarios for the contiguous United States. These scenarios cover the period 1990 to 2100 and provide a basis to assess possible proactive measures for sea-level rise. However, they are subject to the same uncertainties as the global scenarios as most of the sea-level rise will occur decades into the future. When considering what should be done now in response to future sea-level rise, given these large uncertainties, it is best to identify (1) low-cost, no regret responses which would maintain or enhance the choices available to tomorrow's coastal managers; and (2) sectors where reactive adaptation would have particularly high costs and where allowance for future sea-level rise can be considered a worthwhile “insurance policy.”; Sea-level rise will impact an evolving coastal landscape which already is experiencing a range of other pressures. Therefore, to be most effective, responses to sea-level rise need to be integrated with all other planning occurring in the coastal zone

The implications of accelerated sea-level rise and developing countries: a discussion

Any accelerated rise in sea level could have a major impact on the countries considered in this issue; the resulting problems will vary from country to country and depend on coastal geomorphology and present and future human activities in the coastal zone. Based on their highly-populated deltaic areas, China, Bangladesh, and Egypt are highly susceptible to sea-level rise. Sea-level rise could also cause significant problems in Senegal, and particularly Uruguay; this being largely related to tourist-based developments and to the high cost of beach nourishment. Considering the 10 countries contained in this issue, Bangladesh, Senegal, Nigeria, and Egypt appear most vulnerable — that is have the least ability to cope with sea-level rise based on their existing physical and human susceptibility, large and rapidly expanding coastal populations, and limited experience of likely adaptation techniques. Coastal wetlands are expected to experience losses at a global scale given accelerated sea-level rise, exacerbating existing rates of loss due to natural and human-induced factors, such as direct reclamation. The above conclusions are largely based upon the present pattern and distribution of coastal development in these countries. Their rapidly expanding coastal populations make continuing rapid and major coastal development almost certain; without careful planning, this will increase the vulnerability already described. Protection is technically feasible and likely in developed areas; although, increasingly large populations would be dependent on coastal defenses and would face catastrophic consequences in the event of failure. In some deltaic and wetland settings, comprehensive natural system engineering approaches such as controlled flooding and sediment management may be useful. However, there are limits to the ability of humans to counter all the projected losses of coastal wetlands. The uncertainty associated with future sea-level rise demands flexible policies in the coastal zone which can adapt to changing conditions. Sea-level rise exacerbates existing problems, rather than creating fundamentally new problems; thus, these approaches are best integrated with solutions to existing coastal problems. Thus, the coastal implications of climate change are one possible trigger for integrated coastal zone management. This will provide a strategic perspective of the coastal zone and contribute towards its more effective long-term management

Historic evolution of a marsh island: Bloodsworth Island, Maryland

High rates of relative sea-level rise in the Chesapeake Bay of about 0.3 m/century has caused rapid land loss of the Bay islands. This study is the first quantitative analysis of both perimeter and interior land loss for one of the large marsh islands?Bloodsworth Island. A geographical information system (GIS) was used for the analysis at a resolution of about 16 meters. From 1849 to 1992, the area of Bloodsworth Island declined by 579 ha, or 26% of the land area in 1849. The land loss can be divided into four geomorphic types: perimeter land loss, channel widening, channel ponding, and non- channel ponding. Perimeter land loss is largest at 3.0 ha/yr from 1942 to 1992, but the three interior land loss types are also significant, totalling 1.6 ha/yr from 1942 to 1992. Channel ponding and widening were responsible for nearly all interior land loss prior to 1942. The initial formation of non- channel ponds is attributed to a short-term acceleration in sea-level rise (to 7 mm/yr from 1930 to 1948). Subsequently, non-channel ponding has been significant, particularly in the southeastern quadrant of the island. Compared to the mainland marshes, interior land loss has occurred at much slower rates; this is probably due to the low thickness of the marsh deposits on Bloodsworth. To date, bombing appears to have only had a secondary impact on land loss at the scale of this study. In the future, the island appears increasingly vulnerable to interior break- up, particularly given another short-term acceleration of sea-level rise

EP139_2009-02

A preliminary assessment of the Toronto Lake Watershed in southeastern Kansas

EP141_2009-02

A preliminary assessment of the Lower Little Blue Watershed in northeast Kansas

EP140_2009-02

A preliminary assessment of the Lower Big Blue Watershed in northeast Kansas

Erosional and Depositional Characteristics of Regional Overwash Deposits Caused by Multiple Hurricanes

Regional-scale washover deposits along the Florida Gulf and Atlantic coasts induced by multiple hurricanes in 2004 and 2005 were studied through coring, trenching, ground-penetrating radar imaging, aerial photography, and prestorm and poststorm beach-profile surveys. Erosional and depositional characteristics in different barrier-island sub-environments, including dune field, interior wetland and back-barrier bay were examined. Over the eroded dune fields, the washover deposits are characterized by an extensive horizontal basal erosional surface truncating the old dune deposits and horizontal to slightly landward-dipping stratification. Over the marshes in the barrier-island interior, the washover deposits are characterized by steep tabular bedding, with no erosion at the bottom. Overwash into the back-barrier bay produced the thickest deposits characterized by steep, prograding sigmoidal bedding. No significant erosional feature was observed at the bottom. Washover deposits within the dense interior mangrove swamp demonstrate both normal and reversed graded bedding. The washover deposits caused by hurricanes Frances (2004) and Jeanne (2004) along the southern Florida Atlantic coast barrier islands are substantially different from those along the northern Florida barrier islands caused by Ivan (2004) and Dennis (2005) in terms of regional extension, erosional features and sedimentary structures. These differences are controlled by different overall barrier-island morphology, vegetation type and density, and sediment properties. The homogeneity of sediment along the northern Florida coast makes distinguishing between washover deposits from Ivan and Dennis difficult. In contrast, along the Atlantic coast barrier islands, the two overwash events, as demonstrated by two phases of graded bedding of the bimodal sediments, are easily distinguishable