Iowa Spring Flood Outlook

1. Iowa Spring Flood Outlook February 22, 2010 Jeff Zogg

2. Topics • Outlook at-a-glance • Definitions • Current conditions • Latest spring food outlook • Questions

3. Outlook at-a-glance • High risk of significant flooding continues in many areas • At least near to above normal risk of flooding statewide. • Time period when flooding is most likely extends from mid-March into late April. • Above normal risk of flooding from ice jams. • Higher than normal risk of flooding also in areas that have little to no snow cover. • The flooding potential is more sensitive than normal to the occurrence and timing of weather events such as rapid warm ups and heavy precipitation.

4. Definitions

5. Definitions • Stage / Gage height • The level of the water surface of a stream above an established datum at a given location. The established datum may be a local elevation or sea level. • Reach • A section of stream between an upstream and downstream location, for which the stage or flow measured at a point somewhere along the section (e.g., gaging station or forecast point) is representative of conditions in that section of river or stream.

6. Definitions • Bankfull stage • An established gage height at a given location, above which a rise in water surface will cause the river or stream to overflow the river bank somewhere in the corresponding reach. • Flood stage • An established gage height for a given location at which a rise in water surface level begins to create a hazard to lives, property or commerce. The issuance of flood (or in some cases flash flood) warnings is linked to flood stage. Not necessarily the same as bankfull stage.

7. Definitions • Minor flooding • Minimal or no property damage, but possibly some public threat. • Moderate flooding • Some inundation of structures and roads near stream. Some evacuations of people and/or transfer of property to higher elevations. • Major flooding • Extensive inundation of structures and roads. Significant evacuations of people and/or transfer of property to higher elevations.

8. Definitions • Record flooding • Flooding which equals or exceeds the highest stage or discharge observed at a given site during the period of record keeping. The highest stage on record is not necessarily above the other three flood categories – it may be within any of them or even less than the lowest. Stage – flood category relationship

9. Current conditions

10. Winter average temperatures

11. Winter precipitation

12. Snow depth—now

13. Snow depth vs. normal—now

14. Snow water equivalent—now

15. Snow pack—historical (2009)

16. Snow pack—historical (2008)

17. Stream levels—now 14-day average flow

18. Ground frost Observed frost depth

19. Soil moisture—now Soil moisture percentiles Percentile key ~1: near record low <10: much below normal 10 -24: below normal 25-75: normal 76-90: above normal >90: much above normal ~99: near record high

20. Soil moisture—recent Soil moisture percentiles—December 2009 Percentile key ~1: near record low <10: much below normal 10 -24: below normal 25-75: normal 76-90: above normal >90: much above normal ~99: near record high

21. Latest spring flood outlook

22. Assumptions / notes • This outlook is biased toward normal temperatures and precipitation (i.e., climatology) during the outlook period. • If conditions are not near normal then the probabilities in this outlook may not be valid. • Ice jams • Any ice jams which do occur may result in locally higher river stages and rapid river rises. This outlook does not take into account potential flooding from ice jams. Any flooding from ice jams would be above and beyond the flooding potential indicated in this outlook.

23. 50% chance flood category—now

24. 50% chance flood category—last outlook

25. Risk of minor flooding—now West 1/3 of Iowa (Missouri River basin) East 2/3 of Iowa (Mississippi River basin)

26. Risk of minor flooding—first outlook West 1/3 of Iowa (Missouri River basin) East 2/3 of Iowa (Mississippi River basin)

27. Risk of moderate flooding—now West 1/3 of Iowa (Missouri River basin) East 2/3 of Iowa (Mississippi River basin)

28. Risk of moderate flooding—first outlook West 1/3 of Iowa (Missouri River basin) East 2/3 of Iowa (Mississippi River basin)

29. Risk of major flooding—now West 1/3 of Iowa (Missouri River basin) East 2/3 of Iowa (Mississippi River basin)

30. Risk of major flooding—first outlook West 1/3 of Iowa (Missouri River basin) East 2/3 of Iowa (Mississippi River basin)

31. 90-day detail—Waterloo

32. Weekly detail—Waterloo

33. 90-day detail—Cedar Rapids

34. Weekly detail—Cedar Rapids

35. 90-day detail—Humboldt

36. Weekly detail—Humboldt

37. 90-day detail—DSM 2nd Ave

38. Weekly detail—DSM 2nd Ave

39. 90-day detail—DSM Fleur

40. Weekly detail—DSM Fleur

41. 90-day detail—Burlington

42. Weekly detail—Burlington

43. 90-day detail—Spencer

44. Weekly detail—Spencer

45. Detail graphics—notes • The 90-day and weekly detail graphics are available online. • The following slides show how to find this information.

46. Finding river forecast information

47. Finding river forecast information

48. Finding river forecast information

49. Final thoughts

50. Final thoughts • Most homeowners’ insurance policies do not cover flood-related losses. • To cover flood-related losses, flood insurance must typically be purchased. This is in addition to homeowners insurance. • Disaster assistance, if it’s available, is typically a loan that you must repay with interest. • In most cases, flood insurance requires a 30-day waiting period before it becomes effective. • Visit http://www.floodsmart.gov/ for more information.