Table 2.
Populations affected by changes in the flow of baseline 1% AEP floods (millions of persons).
| NCA region | Future flow more than 1.50 times larger than baseline | Future flow the same size to 1.50 times larger than baseline | Future flow smaller than baseline | ||||||
|---|---|---|---|---|---|---|---|---|---|
| Age 0–4 | Age | All ages | Age 0–4 | Age | All ages | Age 0–4 | Age | All ages | |
| RCP4.5 in 2050 | |||||||||
| Northeast | 0.00 | 0.00 | 0.00 | 2.43 | 4.88 | 25.58 | 3.76 | 8.06 | 40.19 |
| Southeast | 0.00 | 0.00 | 0.00 | 4.03 | 9.87 | 44.94 | 3.48 | 8.60 | 38.93 |
| Midwest | 0.00 | 0.00 | 0.00 | 3.14 | 6.04 | 33.35 | 3.46 | 6.78 | 36.32 |
| Northern Great Plains | 0.00 | 0.00 | 0.00 | 0.58 | 1.23 | 6.28 | 0.01 | 0.02 | 0.13 |
| Southern Great Plains | 0.00 | 0.00 | 0.00 | 3.65 | 7.74 | 37.33 | 0.65 | 1.48 | 6.99 |
| Southwest | 0.00 | 0.00 | 0.00 | 6.74 | 14.46 | 68.44 | 0.98 | 2.16 | 10.02 |
| Northwest | 0.00 | 0.00 | 0.00 | 1.21 | 2.69 | 13.09 | 0.07 | 0.14 | 0.70 |
| Total | 0.00 | 0.00 | 0.00 | 21.79 | 46.90 | 229.03 | 12.40 | 27.24 | 133.28 |
| RCP4.5 in 2090 | |||||||||
| Northeast | 0.00 | 0.00 | 0.00 | 4.58 | 8.24 | 45.59 | 2.63 | 4.42 | 26.00 |
| Southeast | 0.00 | 0.00 | 0.00 | 6.64 | 12.92 | 67.43 | 2.51 | 5.21 | 25.97 |
| Midwest | 0.00 | 0.00 | 0.00 | 4.44 | 7.09 | 43.23 | 3.19 | 4.99 | 31.14 |
| Northern Great Plains | 0.00 | 0.00 | 0.00 | 0.69 | 1.25 | 7.01 | 0.04 | 0.05 | 0.35 |
| Southern Great Plains | 0.00 | 0.00 | 0.00 | 3.83 | 7.02 | 37.41 | 1.54 | 3.06 | 15.51 |
| Southwest | 0.02 | 0.12 | 0.31 | 8.71 | 16.07 | 84.52 | 0.98 | 1.84 | 9.58 |
| Northwest | 0.00 | 0.00 | 0.00 | 1.42 | 2.69 | 14.35 | 0.06 | 0.10 | 0.54 |
| Total | 0.02 | 0.12 | 0.31 | 30.30 | 55.28 | 299.53 | 10.94 | 19.67 | 109.09 |
| RCP8.5 in 2050 | |||||||||
| Northeast | 0.00 | 0.00 | 0.00 | 4.85 | 10.21 | 51.58 | 1.34 | 2.73 | 14.19 |
| Southeast | 0.00 | 0.00 | 0.00 | 5.38 | 13.28 | 60.00 | 2.14 | 5.18 | 23.87 |
| Midwest | 0.00 | 0.00 | 0.00 | 3.86 | 7.72 | 40.87 | 2.74 | 5.10 | 28.80 |
| Northern Great Plains | 0.00 | 0.00 | 0.00 | 0.56 | 1.21 | 6.11 | 0.03 | 0.05 | 0.29 |
| Southern Great Plains | 0.00 | 0.00 | 0.00 | 4.01 | 8.56 | 41.26 | 0.28 | 0.65 | 3.07 |
| Southwest | 0.00 | 0.00 | 0.00 | 7.70 | 16.56 | 78.28 | 0.02 | 0.05 | 0.19 |
| Northwest | 0.00 | 0.00 | 0.00 | 1.23 | 2.74 | 13.31 | 0.05 | 0.09 | 0.48 |
| Total | 0.00 | 0.00 | 0.00 | 27.61 | 60.29 | 291.40 | 6.59 | 13.86 | 70.90 |
| RCP8.5 in 2090 | |||||||||
| Northeast | 0.00 | 0.00 | 0.00 | 7.04 | 12.42 | 70.02 | 0.16 | 0.24 | 1.57 |
| Southeast | 0.00 | 0.00 | 0.00 | 8.68 | 17.10 | 88.52 | 0.46 | 1.03 | 4.87 |
| Midwest | 0.00 | 0.00 | 0.00 | 5.68 | 8.87 | 55.12 | 1.94 | 3.21 | 19.24 |
| Northern Great Plains | 0.00 | 0.00 | 0.00 | 0.67 | 1.16 | 6.71 | 0.06 | 0.13 | 0.66 |
| Southern Great Plains | 0.02 | 0.03 | 0.21 | 4.85 | 9.07 | 47.59 | 0.50 | 0.97 | 5.11 |
| Southwest | 5.30 | 9.14 | 50.27 | 4.08 | 8.21 | 40.88 | 0.33 | 0.68 | 3.27 |
| Northwest | 0.09 | 0.15 | 0.87 | 1.35 | 2.59 | 13.72 | 0.03 | 0.05 | 0.30 |
| Total | 5.41 | 9.33 | 51.34 | 32.36 | 59.42 | 322.56 | 3.49 | 6.32 | 35.03 |
Note: AEP, annual exceedance probability; NCA, National Climate Assessment; RCP, representative concentration pathway. Spatially explicit projections of exposure to changes in flow (magnitude) of inland floods (of 1% AEP frequency) were developed by integrating data from 29 global climate models (GCMs) under RCP8.5 and RCP4.5 in the mid- (2040–2059) and late- (2080–2099) 21st century with county-specific projections of U.S. populations for 2050 and 2090. Corresponding county- and state-level data are depicted in Figure 3 and Table S4, respectively. Populations are based on Integrated Climate and Land Use Scenarios (ICLUS) v2 county-level age group projections for the referenced year (i.e., 2050, 2090) (see Table S6 for corresponding projections holding population at 2010 levels and distribution).