Levees and the National Flood Insurance Program (NAP)

The National Academies Press of the United States has recently released a report that will be of interest to those of you concerned with climate change (which better be every one of you dammit!). The report talks about increasing floods due to weather whiplash and sea level rise due to glacial melting (and subsidence), mainly in relation to the levees program and insurance, but also more generally. Here's a small excerpt to give you a flavor:

Community flood risk scenarios will continue to evolve as change occurs. Climate change will have a variety of regional impacts, and the geographic location of a community will affect how changing conditions affect risk. Some areas will have more droughts, some will have more frequent floods, and others will have more intense floods. Research to understand these hydrologic changes is ongoing (NRC, 2011, 2012a). A recent special report of the Intergovernmental Panel on Climate Change (IPCC, 2012) indicates a likely increase in many regions of the frequency of heavy precipitation events, and when coupled with increasing vulnerability presents a myriad of challenges for coping with climate-related disastersIPCC. Galloway (2009) cites 11 major international studies conducted from 1987 to 2002 that all predict significant climate change–induced hazards, including increased flooding, higher mean atmospheric temperatures, higher global mean sea levels, increased precipitation, increased strength of storms, more energetic waves, storm surges that reach further inland, undercapacity of urban sewer- age and drainage systems, increased vulnerability of port cities, and disproportionate impacts on disadvantaged population segments (Galloway, 2009). The rise in sea level and the increase in storm surge due to climate change puts many coastal areas at risk from intensified flooding (NRC, 2010).

Hirsch and Ryberg (2012), in examining trends in annual floods at 200 stream-gauge sites in the United States, found that , while there appeared to be no strong statistical evidence for flood magnitudes increasing with increasing global mean carbon dioxide concentration, there were differences in flood magnitudes among the four quadrants of the conterminous United States (Figure 6-8). They indicate that the attention should be paid to the effects of changes in the relative “importance of the role of snowpack and rain on snow events.” Raff (2013) suggests that the increase in magnitude of floods in the northeastern and midwestern United States (Figure 6-9, Upper Right), may have consequences in the Upper Mississippi, Ohio, and Missouri watersheds (Hirsch and Ryberg, 2012; Raff, 2013).

The Draft National Climate Assessment, issued in January 2013 by the National Climate Assessment Develop- ment Advisory Committee, begins with the statement:

Climate change is already affecting the American people. Certain types of weather events have become more frequent and/or intense, including heat waves, heavy downpours, and, in some regions, floods and droughts. . . . The largest increases have occurred in the Northeast, Midwest, and Great Plains, where heavy downpours have exceeded the capacity of infrastructure such as storm drains, and have led to flooding events and accelerated erosion.

The report goes on to point out the increasing vulnerability to flooding of those in floodplains and coastal areas

You can buy the report for a mere $53, or download it for free. (Downloading from the NAP involves signing in and stuff, but it is pretty easy, though at the moment their server is running a bit slow since they just publicized the report and everybody wants a copy of it.)

Go HERE to get the report.