Riverine Flood Risk in Iowa

All Iowa counties ranked by FEMA National Risk Index riverine flood score

Riverine Flood risk — rivers and streams overflowing their banks after heavy rain or snowmelt — is rated for 99 of 99 Iowa counties in FEMA's National Risk Index. Polk County carries the state's highest riverine flood score at 92.1, with $61M in expected annual riverine flood losses.

No Iowa county reaches the High band for riverine flood, and expected annual losses from riverine flood total roughly $725M statewide. The full ranking below links to each county's complete 18-hazard risk profile.

County Rankings — Riverine Flood

#CountyRiverine Flood ScoreRatingAnn. Freq.Ann. Loss
1 Polk County
92.1
Medium 5.07 / yr $61M
2 Scott County
88.4
Medium 3.46 / yr $40M
3 Linn County
86.7
Medium 2.21 / yr $36M
4 Johnson County
79.8
Medium 1.96 / yr $27M
5 Woodbury County
78.2
Medium 2.21 / yr $18M
6 Black Hawk County
76.6
Medium 4.50 / yr $20M
7 Pottawattamie County
74.6
Medium 1.25 / yr $18M
8 Lee County
70.4
Low 2.36 / yr $13M
9 Wapello County
69.3
Low 3.32 / yr $12M
10 Story County
69.1
Low 2.68 / yr $16M
11 Cerro Gordo County
69.0
Low 2.21 / yr $12M
12 Clinton County
66.9
Low 2.54 / yr $12M
13 Dubuque County
65.4
Low 1.64 / yr $19M
14 Marshall County
63.1
Low 2.43 / yr $10M
15 Muscatine County
62.6
Low 2.54 / yr $10M
16 Delaware County
61.7
Low 1.21 / yr $10M
17 Dallas County
60.4
Low 4.25 / yr $17M
18 Fayette County
59.2
Low 1.68 / yr $8M
19 Clayton County
58.0
Low 4.36 / yr $9M
20 Floyd County
56.3
Low 1.82 / yr $8M
21 Crawford County
56.1
Low 0.82 / yr $9M
22 Des Moines County
56.0
Low 2.86 / yr $8M
23 Clay County
53.8
Low 3.64 / yr $11M
24 Hardin County
52.9
Low 1.71 / yr $7M
25 Allamakee County
50.5
Low 1.61 / yr $6M
26 Dickinson County
49.9
Low 2.75 / yr $8M
27 Sioux County
49.5
Low 3.29 / yr $11M
28 Washington County
48.4
Low 1.68 / yr $6M
29 Winneshiek County
47.5
Low 1.50 / yr $8M
30 Webster County
47.1
Low 3.82 / yr $7M
31 Jones County
46.4
Low 1.39 / yr $9M
32 Plymouth County
45.2
Low 3.36 / yr $6M
33 Cass County
43.4
Low 1.25 / yr $4M
34 Jackson County
43.3
Low 1.39 / yr $7M
35 Tama County
42.4
Low 1.54 / yr $5M
36 Marion County
41.2
Low 3.43 / yr $7M
37 Hamilton County
41.0
Low 2.18 / yr $6M
38 Van Buren County
40.8
Low 1.29 / yr $4M
39 Benton County
40.3
Low 1.18 / yr $8M
40 Jasper County
40.2
Low 1.79 / yr $6M
41 Chickasaw County
39.6
Low 1.25 / yr $5M
42 Cherokee County
39.1
Low 1.89 / yr $5M
43 Buchanan County
38.6
Low 2.11 / yr $7M
44 Carroll County
37.5
Low 1.82 / yr $5M
45 Butler County
37.2
Low 3.21 / yr $7M
46 Harrison County
37.0
Low 0.89 / yr $4M
47 Madison County
36.6
Low 1.43 / yr $4M
48 Mahaska County
36.4
Low 3.96 / yr $5M
49 Mitchell County
36.2
Low 1.14 / yr $5M
50 Warren County
35.9
Low 2.86 / yr $7M
51 Wright County
35.1
Low 1.86 / yr $4M
52 Montgomery County
34.6
Very Low 0.93 / yr $4M
53 Bremer County
33.4
Very Low 1.46 / yr $7M
54 Buena Vista County
32.9
Very Low 2.07 / yr $4M
55 Davis County
32.7
Very Low 0.96 / yr $3M
56 Iowa County
32.6
Very Low 1.89 / yr $4M
57 Union County
30.1
Very Low 1.04 / yr $3M
58 Appanoose County
30.0
Very Low 1.71 / yr $3M
59 Keokuk County
29.6
Very Low 1.32 / yr $4M
60 Boone County
28.8
Very Low 1.71 / yr $6M
61 Cedar County
27.6
Very Low 0.96 / yr $5M
62 Page County
27.5
Very Low 0.71 / yr $3M
63 Mills County
27.4
Very Low 0.96 / yr $5M
64 Kossuth County
26.7
Very Low 2.57 / yr $5M
65 Henry County
26.7
Very Low 0.82 / yr $3M
66 Winnebago County
25.6
Very Low 1.18 / yr $3M
67 Howard County
25.4
Very Low 1.04 / yr $4M
68 Monona County
25.0
Very Low 0.64 / yr $3M
69 Adair County
23.8
Very Low 1.32 / yr $2M
70 Lucas County
22.7
Very Low 3.21 / yr $2M
71 Guthrie County
22.0
Very Low 1.79 / yr $4M
72 Hancock County
21.6
Very Low 1.39 / yr $3M
73 Taylor County
20.9
Very Low 1.00 / yr $2M
74 Louisa County
20.9
Very Low 2.25 / yr $3M
75 Calhoun County
20.6
Very Low 1.79 / yr $2M
76 Emmet County
20.4
Very Low 2.71 / yr $3M
77 Jefferson County
20.4
Very Low 0.68 / yr $2M
78 Poweshiek County
20.3
Very Low 0.89 / yr $3M
79 Audubon County
19.8
Very Low 0.96 / yr $2M
80 Lyon County
19.6
Very Low 2.36 / yr $4M
81 Shelby County
19.5
Very Low 0.14 / yr $4M
82 Humboldt County
18.9
Very Low 2.79 / yr $3M
83 O'Brien County
18.5
Very Low 1.46 / yr $4M
84 Ida County
18.4
Very Low 0.71 / yr $2M
85 Fremont County
18.4
Very Low 2.36 / yr $2M
86 Pocahontas County
18.1
Very Low 1.50 / yr $2M
87 Sac County
17.2
Very Low 1.61 / yr $3M
88 Decatur County
15.8
Very Low 1.82 / yr $2M
89 Osceola County
14.9
Very Low 0.36 / yr $2M
90 Grundy County
14.2
Very Low 1.61 / yr $3M
91 Wayne County
14.0
Very Low 2.71 / yr $1M
92 Franklin County
14.0
Very Low 1.54 / yr $2M
93 Greene County
12.0
Very Low 1.93 / yr $2M
94 Adams County
11.5
Very Low 0.96 / yr $2M
95 Worth County
10.7
Very Low 1.11 / yr $2M
96 Clarke County
9.6
Very Low 1.82 / yr $2M
97 Monroe County
9.1
Very Low 1.64 / yr $2M
98 Palo Alto County
9.0
Very Low 1.86 / yr $2M
99 Ringgold County
5.0
Very Low 0.79 / yr $985K

99 Iowa counties with measurable riverine flood risk. See the national riverine flood ranking or all Iowa counties by overall risk.

Frequently Asked Questions

Which Iowa county has the highest riverine flood risk?

Polk County has the highest FEMA riverine flood risk score in Iowa at 92.1 (Medium), with $61M in expected annual losses and about 5.07 events per year.

How many Iowa counties face significant riverine flood risk?

99 Iowa counties record measurable riverine flood risk in FEMA's National Risk Index; 0 of them are rated High or Very High.

Other Hazards in Iowa

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